PART II: CUVELAI AREA of NAMIBIA INTERIM REPORT No. 1: WATER
`
REPUBLIC OF NAMIBIA
MINISTRY OF AGRICULTURE, WATER AND FORESTRY
EoI 1/18/2 – 02/2011
A PRE-FEASIBILITY STUDY INTO: THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI
PART II: CUVELAI AREA OF NAMIBIA
INTERIM REPORT No. 1: WATER DEMANDS AND WATER RESOURCES
25 JULY 2014
SUBMITTED BY:
IN JOINT VENTURE WITH
WITH SUB-CONSULTANTS
ENVES
AND OTHERS THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
PREFACE
Namibia is an arid country where water supply is the primary limiting factor to development. As with most parts of the country, both the Central and the Cuvelai Areas of Namibia experience an annual water deficit since evaporation rates far exceed the average annual rainfall.
Both the Central Area of Namibia and the Cuvelai area play very important roles in the social and economic development of the country, as both areas experience population and economic growth rates well above the average for Namibia. Both areas are prone (presently and in the near future) to water supply interruptions which would jeopardise prospective new economic growth.
Most of the water sources within the Central Area of Namibia and the Cuvelai have been developed and are nearing the limit of their supply potential. Further development and growth in both the CAN and the Cuvelai, and by extension in Namibia as a whole, is dependent on securing the long-term water supply for current and prospective future consumers. Failure to ensure adequate water supplies to these areas will result in reduced economic activity with serious social and economic consequences for the continued development of Namibia and its people (WTC, 1997a).
The long-term water security for the Central Area of Namibia and the Cuvelai area and their inhabitants necessitates a further investigation into alternative, additional and / or new sources of supply. Such an investigation must be undertaken and the recommended measures implemented before any shortfall occurs, which on the basis of recent demand modelling, is projected to occur around 2020, provided that the Windhoek Managed Aquifer Recharge project is fully developed as soon as possible (for the Central Area of Namibia).
The main objective of this Pre-Feasibility Study is to examine all the nominally feasible options for augmenting the water supply to the Central and the Cuvelai Areas of Namibia where existing sources might become inadequate in the near future. In terms of alleviating the supply shortfalls which are expected to occur in the future, additional water sources are to be examined on the basis of augmentation and back-up – i.e. whether the proposed source and / or scheme is to serve for augmentation and / or supply, is to be investigated.
This Pre-Feasibility Study will be undertaken in three main phases as follows:
1. Phase 1: Investigations and Water Demands, 2. Phase 2: Modelling and Concept Schemes, 3. Phase 3: Engineering and Environmental Evaluations.
The Interim Reports No. 1, submitted in two parts; Part I which deals with the Central Area of Namibia and Part II which deals with the Cuvelai Area of Namibia, mark the milestones for the conclusion of Phase 1 of the Pre-Feasibility Study. Interim Reports No. 1 provide details of the water demands in and water resources currently and potentially available to the Central and Cuvelai Areas of Namibia.
Preface I THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
INDEX TO ALL VOLUMES
The Interim Reports for Phase 1 of this Pre-Feasibility Study are submitted in two parts; Part I deals with the Central Area of Namibia and Part II deals with the Cuvelai Area of Namibia.
Part I: Central Area of Namibia Part II: Cuvelai Area of Namibia Volume 1 Volume 1 Chapter 1 Project Background Chapter 1 Project Background Chapter 2 Overview of Namibia Chapter 2 Overview of Namibia Chapter 3 Introduction to the Central Area of Chapter 3 Introduction to the Cuvelai Area of
Namibia Namibia Chapter 4 Water Resources and Supply Chapter 4 Water Resources Available to the Infrastructure in the Central Area Cuvelai Area of Namibia Chapter 5 Water Demand Projections in the Chapter 5 Water Supply Infrastructure in the
Central Area of Namibia Cuvelai Area Chapter 6 Water Demands Along the Chapter 6 Historic Water Consumption in the
Eastern National Water Carrier Cuvelai Area Chapter 7 Water Demands Supplied by the Chapter 7 Water Demands in the Cuvelai Area
Von Bach Water Treatment Plant Chapter 8 Raw Water Demands: Von Bach – Chapter 13 Approval of Report and Swakoppoort – Okongava and Recommendations Navachab Mine Chapter 9 Water Demands Supplied by the
Karibib Water Treatment Plant Chapter 10 Other Towns and Centres not Linked to the Central Area Water Supply System Chapter 11 Other Towns with own Water Resources not Linked to the CAN System Chapter 12 Summary of Water Demands in
the Central Area of Namibia Chapter 13 Approval of Report and
Recommendations
Index to All Volumes I THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
CONTENTS
PREFACE I INDEX TO ALL VOLUMES I CONTENTS i TABLES IN TEXT vi FIGURES IN TEXT ix ABBREVIATIONS xii GLOSSARY OF TERMS xvii REFERENCES xxi
CHAPTER 1 : INTRODUCTION 1-1 1.1 PROJECT BACKGROUND 1-1 1.1.1 Project Advertisement and Award 1-1 1.1.2 Engineering, Environmental and Social Consultants and External Reviewers 1-2 1.2 PROJECT AREA 1-3 1.2.1 The Central Area of Namibia 1-5 1.2.2 The Cuvelai Area of Namibia 1-6 1.3 PROJECT OBJECTIVE 1-7 1.4 OVERALL PROJECT APPROACH AND METHODOLOGY 1-7 1.4.1 Overall Project Methodology 1-7 1.4.2 Underlying Approach to this Study 1-8 1.4.3 Planning Horizon 1-8 1.4.4 Client Liaison 1-9
CHAPTER 2 : OVERVIEW OF NAMIBIA 2-1 2.1 OVERVIEW OF NAMIBIA 2-1 2.1 CLIMATE AND GEOLOGY 2-1 2.2.1 The Climatic Systems of Southern Africa 2-1 2.2.2 The Köppen-Geiger Climate Classification 2-2 2.2.3 Rainfall 2-4 2.2.4 Temperature 2-7 2.2.5 Evaporation of Water Deficit 2-7 2.2.6 Geology, Elevation, Relief and Soils 2-9 2.3 POPULATION AND DEMOGRAPHICS 2-13 2.3.1 Namibia's Population 2-13 2.3.2 Analysis of Population and Income Levels 2-15 2.3.3 The Effect of HIV/AIDS on Population Growth (UNDP Website 2014) 2-16 2.3.4 Population Growth Rates 2-17
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CONTENTS (continued)
2.4 WATER RESOURCES 2-20 2.4.1 Surface Water 2-20 2.4.2 Groundwater 2-24 2.4.3 Unconventional Water Resources 2-27 2.4.4 Inter-Basin Transfers 2-30 2.5 THE WATER SUPPLY DILEMMA IN NAMIBIA 2-31 2.6 WATER DEMAND PROJECTIONS 2-33 2.6.1 General 2-33 2.6.2 Factors Which Influence Water Demand 2-35 2.6.3 Water Demand Norms Used 2-35 2.7 LEGISLATIVE AND POLICY ENVIRONMENT 2-37 2.7.1 National Legislation and Policies 2-37 2.7.2 Regional Policies and Agreements 2-42 2.7.3 International Law and Principles 2-42
CHAPTER 3 : INTRODUCTION TO THE CUVELAI AREA 3-1 3.1 PROJECT AREA IN THE CUVELAI 3-1 3.1.1 Introduction 3-1 3.1.2 Climate 3-2 3.1.3 Biophysical Environment 3-4 3.1.4 Water Supply 3-11 3.1.5 Population 3-11 3.2 ECONOMIC & OTHER IMPORTANCE OF THE CUVELAI AREA 3-14 3.2.1 Population Growth and Private Consumption 3-14 3.2.2 Building and Construction in Oshakati 3-14 3.3 HISTORY OF WATER SUPPLY IN THE CUVELAI 3-15 3.3.1 The Assessment and Planning of Water Supply Infrastructure in the Cuvelai 3-15 3.3.2 Use of Surface Water Sources 3-27 3.3.3 Groundwater in the Cuvelai Area 3-33 3.3.4 Current Water Supply Situation in the Cuvelai 3-34 3.4 BILATERAL RELATIONS REGARDING THE KUNENE RIVER 3-35 3.4.1 Bilateral Agreements 3-35 3.4.2 Permanent Joint Technical Commission 3-37 3.4.3 Terms of Reference of the Permanent Joint Technical Commission 3-38 3.4.4 Kunene Transboundary Water Supply Project 3-39
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CONTENTS (continued)
CHAPTER 4 : WATER RESOURCES AVAILABLE TO THE CUVELAI AREA 4-1 4.1 CURRENTLY USED WATER RESOURCES 4-1 4.2 THE KUNENE RIVER 4-1 4.2.1 The Kunene River Basin 4-1 4.2.2 Hydrology 4-9 4.2.3 Dams on the Kunene River 4-18 4.2.4 Water Quality 4-22 4.2.5 Proposed Developments in the Kunene River Basin 4-23 4.3 SURFACE FLOW IN THE CUVELAI BASIN 4-24 4.3.1 Major Drainage Zones in the Cuvelai 4-24 4.3.2 Floods in the Cuvelai System 4-28 4.3.3 Potential use of the Surface Flow in the Cuvelai 4-31 4.4 GROUNDWATER IN THE CUVELAI AREA 4-32 4.4.1 Introduction 4-32 4.4.2 Hydrogeology 4-34 4.4.3 Aquifer Characteristics 4-37 4.4.4 Groundwater Sub-Basins 4-44 4.4.5 Water Quality 4-47 4.4.6 Groundwater Supply Potential 4-53 4.4.7 Summary of the Potential of Groundwater in the Cuvelai Etosha Basin 4-54 4.4.8 Current Utilisation of Groundwater Resources in the Cuvelai Area 4-56 4.4.9 Recharge 4-57
CHAPTER 5 : WATER SUPPLY INFRASTRUCTURE IN THE CUVELAI AREA 5-1 5.1 BASIC LAYOUT OF WATER SUPPLY INFRASTRUCTURE IN THE CUVELAI AREA 5-1 5.1.1 Introduction 5-1 5.1.2 Separation of Schemes and Water Supply Zones 5-2 5.2 INFRASTRUCTURE AT CALUEQUE 5-4 5.2.1 Calueque Dam 5-4 5.2.2 Calueque Pump Station 5-8 5.2.3 Calueque Pipeline 5-9 5.2.4 Summary of the Raw Water Abstraction Capacity at Calueque 5-10 5.3 CALUEQUE - OSHAKATI CANAL 5-11 5.4 OLUSHANDJA DAM AND THE ETAKA CANAL 5-14 5.4.1 Olushandja Dam 5-14 5.4.2 Etaka Canal 5-17 5.5 WATER PURIFICATION PLANTS 5-18
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CONTENTS (continued)
5.6 NAMWATER'S PIPELINES, PUMP STATIONS AND RESERVOIRS 5-20 5.6.1 Extent of NamWater's Bulk Transfer Infrastructure 5-20 5.6.2 Capacity of the Major Pipeline Arteries 5-20 5.7 RURAL WATER SUPPLY PIPELINE SCHEMES 5-21 5.8 EXTENT OF THE BOREHOLE INFRASTRUCTURE 5-22
CHAPTER 6 : HISTORIC WATER CONSUMPTION IN THE CUVELAI AREA 6-1 6.1 WATER CONSUMPTION AND HISTORIC SALES DATA 6-1 6.1.1 Pipeline and Borehole Potable Water Use 6-1 6.1.2 Irrigation Water 6-1 6.1.3 NamWater's Historic Sales Data 6-1 6.2 HISTORIC WATER CONSUMPTION 6-2 6.2.1 Historic Monthly Consumption 6-2 6.2.2 Historic Annual Consumption 6-3 6.2.3 Water Consumption by Consumer Category 6-4 6.2.4 Urban and Rural Water Consumption 6-9 6.2.5 Irrigation Water Consumption 6-10 6.3 NUMBER OF WATER CONSUMERS IN THE CUVELAI AREA 6-12 6.3.1 Determination of the Number of Billed Consumers 6-12 6.3.2 Number of Billed Consumers 6-12 6.4 WATER BALANCE FOR THE CUVELAI AREA 6-14 6.4.1 Volumes Abstracted at the Calueque Dam 6-14 6.4.2 Comparison of the Water Abstraction and Water Sales 6-15
CHAPTER 7 : WATER DEMANDS IN THE CUVELAI AREA 7-1 7.1 OVERVIEW OF THE ESTIMATION OF THE WATER DEMANDS 7-1 7.1.1 Zonal Division 7-1 7.1.2 Demand Scenarios 7-1 7.1.3 Water Demands and Losses 7-1 7.2 POPULATION AND POPULATION GROWTH RATES 7-3 7.2.1 Total Population and Growth Rates 7-3 7.2.2 Urban Population and Growth Rates 7-3 7.2.3 Rural Population and Growth Rates 7-4 7.2.4 Selected Population Growth Rates for the Cuvelai Area 7-5 7.3 FUTURE DEVELOPMENT CONSIDERATIONS 7-9 7.3.1 Known and Unknown Future Developments 7-9 7.3.2 Ruacana South Rural Water Supply Project 7-9 7.3.3 King Kaluma Rural Water Supply Project 7-10 7.3.4 Expansion of the Etunda Irrigation Area 7-11
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CONTENTS (continued)
7.4 ESTIMATION OF THE URBAN WATER DEMANDS 7-12 7.7.4 Defined Urban Areas 7-12 7.4.2 Population and Institutional Areas by Water Supply Zone 7-13 7.4.3 Income Distribution Factors 7-13 7.4.4 Water Demand Norms 7-14 7.4.5 Current Urban Water Demand Estimation 7-14 7.4.6 Adopted Urban Water Demand for 2012/13 7-14 7.4.7 Projected Future Urban Water Demands for the Cuvelai Area 7-16 7.5 ESTIMATION OF THE RURAL WATER DEMANDS 7-17 7.5.1 Defined Rural Areas 7-17 7.5.2 Rural Population and Livestock Numbers 7-18 7.5.3 Water Demand Norms 7-20 7.5.4 Current Rural Water Demand Estimation 7-21 7.5.5 Adopted Rural Water Demand for 2012/13 7-23 7.5.6 Projected Future Rural Water Demands 7-23 7.6 COMBINED URBAN AND RURAL DEMANDS 7-25 7.7 ESTIMATION OF IRRIGATION DEMANDS 7-26 7.7.1 Defined Irrigation Areas 7-26 7.7.2 Water Demand Norms 7-27 7.7.3 Current Demand Estimation 7-27 7.7.4 Adopted Irrigation Water Demand 7-27 7.7.5 Projected Future Irrigation Water Demands 7-27 7.8 TOTAL CURRENT AND FUTURE DEMANDS OF THE CUVELAI AREA 7-29 7.9 TOTAL CURRENT AND FUTURE WATER SUPPLY AND ABSTRACTION REQUIREMENTS FOR THE CUVELAI AREA 7-30 7.9.1 Water Supply Requirements 7-30 7.9.2 Abstraction Requirements at Calueque 7-31 7.9.3 Future Required Abstraction at Calueque Dam 7-33 7.9.4 Summary of the Projected Water Demands and Abstraction Requirements 7-33
CHAPTER 8 : APPROVAL OF REPORT AND RECOMMENDATIONS 8-1
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TABLES IN TEXT
Table 2.1 Rainfall and Evaporation Date for Selected SADC Countries (Pallet, 1997) 2-4 Table 2.2 2009/10 Namibia Household Income and Expenditure Survey (NSA, 2012b) 2-16 Table 2.3 Regional Growth Rates According to 2011 Census Data 2-19 Table 2.4 Urban Population Growth Rates in the Study Area 2-19 Table 2.5 Estimated Runoff in Ephemeral Rivers in the Interior of Namibia 2-22 Table 2.6 Runoff in Perennial Rivers Bordering Namibia 2-23 Table 2.7 Groundwater Resources which Supply the Central Area of Namibia 2-25 Table 2.8 Types of Water Demand Projections and Major Applications (PI, undated) 2-34 Table 2.9 Domestic and Other Non-Domestic Water Consumption Norms 2-36 Table 2.10 Norms for Agricultural Use 2-36 Table 3.1 Geological Formations in North Central Namibia 3-6 Table 3.2 2011 Population of the Ohangwena, Omusati, Oshana and Oshikoto Regions 3-12 Table 3.3 2011 Urban Population of the Ohangwena, Omusati, Oshana and Oshikoto Regions 3-13 Table 3.4 Value of Projects Implemented by the Oshakati Town Council in 2013/14 3-15 Table 4.1 Catchment Area and Long-Term Mean Annual Runoff for Gauges on the Kunene River (1961 – 1972) (Pitman and Midgley, 1974) 4-11 Table 4.2 Summary of the Characteristics of the Structures on the Kunene River (KUNRAK, DWA, 1991) 4-19 Table 4.3 Flow Categories and Occurrences in the Cuvelai (DWA, 1968) 4-30 Table 4.4 Aquifer Names and related Geological Formations 4-36 Table 4.5 Summary of the Groundwater Potential in the Cuvelai Area (Mendelsohn et al., 2013) 4-56 Table 4.6 Groundwater Utilisation in the Cuvelai-Etosha Basin (2010) 4-56 Table 5.1 Design Flood Peaks for Calueque Dam (LCE, 1992a) 5-6 Table 5.2 Capacity of Raw Water Abstraction and Transfer Infrastructure at Calueque 5-10 Table 5.3 Summary of the Properties of the Calueque – Oshakati Canal 5-13 Table 5.4 Characteristics of Olushandja Dam (NamWater, 2004) 5-16 Table 5.5 Summarised Details of the Purification Plants in the Cuvelai Area (LCE, 2009) 5-19 Table 5.6 Extent of NamWater’s Bulk Water Supply Infrastructure in the Cuvelai Area (LCE, 2009) 5-20 Table 5.7 Capacity of the Major Pipeline Arteries in the Cuvelai Area (LCE, 2009) 5-21 Table 5.8 Extent of the Rural Water Supply Pipeline Schemes (LCE, 2011) 5-22 Table 6.1 Consumption in the Cuvelai Area by Different Categories per Volume, Excluding Irrigation 6-6
Table of Contents vi THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
TABLES (continued)
Table 6.3 Annual Urban and Rural Sales Volumes for the Cuvelai Area 6-9 Table 6.4 Irrigation Sales Volumes per Irrigation Scheme in the Cuvelai Area (Mm3/a) 6-11 Table 6.5 Billed Consumers in Different Categories as a Percentage of the Total 6-13 Table 6.6 Volume of Non-Revenue Water and Percentage of the Total Volume Abstracted at Calueque 6-16 Table 7.1 Water Demand Scenario Details 7-2 Table 7.2 Summary of Overall Population and the Population Growth Rates in the Ohangwena, Omusati, Oshana and Oshikoto Regions (NSA, 2012) 7-3 Table 7.3 Summary of Urban Population and Growth in the Ohangwena, Omusati, Oshana and Oshikoto Regions (NSA, 2012) 7-3 Table 7.4 Summary of Rural Population and Growth in the Ohangwena, Omusati, Oshana and Oshikoto Regions (NSA, 2012) 7-4 Table 7.5 Population Growth Rate Assumptions for the Cuvelai Area 7-8 Table 7.6 2011 Population per Urban Area in the Cuvelai Area (2011 Census) 7-12 Table 7.7 Estimated Current (2012/13) Zonal Population and Institutional Area Values 7-13 Table 7.8 Assumed Income Distribution per Demand Scenario 7-13 Table 7.9 Assumed Urban Water Demand Norms per Demand Scenario 7-14 Table 7.10 Estimated Current (2012/13) Urban Water Demands for the Cuvelai Area 7-15 Table 7.11 Future Urban Water Demands for 2049/50 per Demand Scenario 7-16 Table 7.12 Rural Area Size According to the 2011 Census GIS Data 7-17 Table 7.13 Estimated Current (2012/13) Domestic Rural Population in the Cuvelai Area 7-18 Table 7.14 Estimated Current (2012/13) Number of Scholars for the Cuvelai Area 7-19 Table 7.15 Estimated Current (2012/13) Number of Clinic Out Patients for the Cuvelai Area 7-19 Table 7.16 Estimated Current Number of Livestock for the Cuvelai Area 7-20 Table 7.17 Assumed Rural Water Demand Norms per Demand Scenario 7-20 Table 7.18 Estimated Current (2012/13) Rural Water Demands for the Cuvelai Area 7-22 Table 7.19 Estimated Current (2012/13) Rural Population and Livestock Information for the Additional Schemes in the Cuvelai Area 7-23 Table 7.20 Future Rural Theoretical Demands for 2049/2050 per Demand Scenario 7-24 Table 7.21 Estimated Current (2012/13) Irrigation Water Demand for the Cuvelai Area 7-27 Table 7.22 Future Irrigation Demands for the Cuvelai Area for 2049/50 7-28 Table 7.23 Estimated Current (2012/13) Water Supply Requirements for the Cuvelai Area 7-30 Table 7.24 Future (2049/50) Water Supply Requirements in the Cuvelai Area 7-31 Table 7.25 Variable Proportions of Non-Revenue Water for the Different Demand Scenarios 7-32
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TABLES (continued)
Table 7.26 Estimated Current (2012/13) Abstraction Requirements for the Cuvelai Area at Calueque 7-32 Table 7.27 Estimated Future (2049/50) Abstraction Requirements for the Cuvelai Area at Calueque 7-33
Table of Contents viii THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
FIGURES IN TEXT
Figure 1.1 Preliminary Extent of the Study Area 1-4 Figure 1.2 Schematic Layout of the Bulk Water Supply Infrastructure in the CAN 1-5 Figure 1.3 Layout of the Water Supply Infrastructure in the Cuvelai Area 1-6 Figure 2.1 Köppen-Geiger Climate Classification for Africa (Wikipedia) 2-3 Figure 2.2 Median Annual Rainfall in Namibia (Mendelsohn et al., 2009) 2-5 Figure 2.3 Variation in Rainfall across Africa (Mendelsohn et al., 2009) 2-6 Figure 2.4 Variation in Rainfall across Africa (Mendelsohn et al., 2009) 2-6 Figure 2.5 Average Annual Evaporation in Namibia (Mendelsohn et al., 2009) 2-8 Figure 2.6 Average Annual Water Deficit in Namibia (Mendelsohn et al., 2009) 2-9 Figure 2.7 Major Geological Divisions and Groups in Namibia (Mendelsohn et al., 2009) 2-11 Figure 2.8 Rock Types in Namibia 2-12 Figure 2.9 Dominant Soils in Namibia 2-13 Figure 2.10 Population Density across Namibia (Mendelsohn et al., 2009) 2-14 Figure 2.11 Rivers, Basins, Pans and Lakes (Mendelsohn et al., 2009) 2-21 Figure 2.12 Perennial Rivers and the Cuvelai System (Mendelsohn et al., 2009) 2-23 Figure 2.13 Groundwater Basins of Namibia 2-26 Figure 2.14 Types of Aquifers and their Productivity (DWA, 2001) 2-26 Figure 2.15 Types of Aquifers and their Productivity (Mendelsohn et al., 2009) 2-27 Figure 2.16 Major Water Supply Schemes in Namibia (Mendelsohn et al., 2009) 2-32 Figure 3.1 Location of the Cuvelai Area of Namibia 3-1 Figure 3.2 The Cuvelai-Etosha Basin 3-2 Figure 3.3 Average Annual Rainfall across the Cuvelai Area (Mendelsohn et al., 2000) 3-3 Figure 3.4 Geology of the Cuvelai Basin 3-5 Figure 3.5 Drainage System of the Cuvelai Basin (Mendelsohn et al., 2000) 3-8 Figure 3.6 Soils in the Cuvelai Basin (Mendelsohn et al., 2000) 3-9 Figure 3.7 Vegetation in the Cuvelai Basin (Mendelsohn et al., 2000) 3-10 Figure 3.8 Distribution of Population Densities (2008) (LCE,2011) 3-12 Figure 3.9 Proposed Route of the Okavango – Oshakati Pipeline (TIDI, 1998) 3-22 Figure 3.10 Proposed Route of the Okavango – Okankolo Pipeline (TIDI, 1998) 3-23 Figure 3.11 Typical Excavation Dam Layout (DWA, 1991) 3-28 Figure 3.12 Typical Section through a Pumped Storage Facility (DWA, 1991) 3-29 Figure 3.13 Water Demand Zones in the Cuvelai (DWA, 1991) 3-31 Figure 3.14 Coverage of Bulk Water Supply Infrastructure in the Cuvelai in 1990 3-31 Figure 3.15 Increased Coverage of Water Services in the Cuvelai Area 1990 to 2003 3-32 Figure 3.16 Current (2009) Extent of the Bulk Water Supply Network (Canals, Pipelines and Pump Stations in the Cuvelai (LCE, 2009) 3-32 Figure 3.17 Major Groundwater Areas in the Cuvelai (DWA, 1991) 3-34 Figure 3.18 Organisational Structure of the PJTC (KUNENERAK) 3-39
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FIGURES (continued)
Figure 4.1 The Kunene River Basin (KUNENERAK) 4-2 Figure 4.2 The Kunene River Elevation Profile (KUNENERAK) 4-3 Figure 4.3 Sub-Basins of the Kunene River (KUNENERAK) 4-3 Figure 4.4 Climate Classification for the Kunene River Basin (KUNENERAK) 4-4 Figure 4.5 Precipitation Across the Kunene River Basin (KUNENERAK) 4-5 Figure 4.6 Upper Kunene Sub-Catchment (KUNENERAK) 4-6 Figure 4.7 Middle Kunene Sub-Catchment (KUNENERAK) 4-7 Figure 4.8 Lower Kunene Sub-Catchment (KUNENERAK) 4-8 Figure 4.9 Daily Flow Rates (m3/s) Recorded at Ruacana 4-12 Figure 4.10 Daily Flow Rates (m3/s) Recorded at Ruacana per Hydrological Year 4-13 Figure 4.11 Daily Flow Rates (m3/s) Recorded at Ruacana per Hydrological Year (Selected Years) 4-13 Figure 4.12 Comparison of Average Monthly Volumes of Flow (Mm3/m) at Ruacana from Different Periods 4-14 Figure 4.13 Average Monthly Volumes of Flow (Mm3/m) at Calueque and Ruacana 4-16 Figure 4.14 Comparison of Flow in the Kunene River and Water Sales in the Cuvelai Area (Monthly Values as a percentage of Annual Totals) 4-17 Figure 4.15 Location of Existing and Proposed Infrastructure in the Kunene River Basin (KUNENERAK) 4-18 Figure 4.16 Major Drainage Zones in the Cuvelai Basin (Mendelsohn et al., 2013) 4-25 Figure 4.17 Flooding the Cuvelai Area 4-29 Figure 4.18 Flood Levels in the Cuvelai (Mendelsohn et al., 2013) 4-31 Figure 4.19 Location of the Main Aquifer Systems in the Cuvelai Area (BGR) 4-35 Figure 4.20 Schematic Layout of the Ohangwena Aquifers (after BGR, 2013) 4-39 Figure 4.21 Groundwater Sub-Basins, Existing Water Supply Infrastructure and Elevations (LCE, 2011) 4-45 Figure 4.22 Borehole Depths in the Cuvelai Area (m) 4-45 Figure 4.23 Water Levels in the Cuvelai Area Boreholes (m bgl) 4-46 Figure 4.24 Yields of the Boreholes in the Cuvelai Area (m3/h) 4-46 Figure 4.25 Total Dissolved Solids Concentrations in the Cuvelai Groundwater (mg/ℓ) 4-48 Figure 4.26 Calcium Concentrations in the Cuvelai Groundwater (Ca in mg/ℓ) 4-48 Figure 4.27 Magnesium Concentrations in the Cuvelai Groundwater (Mg in mg/ℓ) 4-49 Figure 4.28 Chloride Concentrations in the Cuvelai Groundwater (Cl in mg/ℓ) 4-50 Figure 4.29 Fluoride Concentrations in the Cuvelai Groundwater (F in mg/ℓ) 4-51 Figure 4.30 Nitrate Concentrations in the Cuvelai Groundwater (N in mg/ℓ) 4-52
Figure 4.31 Sulphates Concentrations in the Cuvelai Groundwater (SO4 in mg/ℓ) 4-53 Figure 4.32 Block diagram showing recharge in the southern Cuvelai Basin (DWA, 2001) 4-57
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FIGURES (continued)
Figure 5.1 Layout of the Water Supply Infrastructure in the Cuvelai Area 5-1 Figure 5.2 Schematic Layout of the Bulk Water Infrastructure in the Cuvelai Area (LCE, 2009) 5-3 Figure 5.3 Eight Water Supply Zones in the Cuvelai Area (LCE, 2009) 5-4 Figure 5.4 Aerial View of Calueque Dam (LCE, 2011) 5-5 Figure 5.5 Calueque Dam 5-6 Figure 5.6 Layout of Skimming Weir and Diversion Canal at Calueque Dam (NamWater, 2004) 5-7 Figure 5.7 Storage and Surface Area Curves of Calueque Dam (LCE, 1992a) 5-8 Figure 5.8 Calueque Pump Station: View Into Pump Well Showing the Electric Motors 5-9 Figure 5.9 Calueque Pipeline 5-10 Figure 5.10 Portions of the Calueque – Oshakati Canal 5-11 Figure 5.11 Schematic Layout of the Calueque – Oshakati Canal (LCE, 2009) 5-12 Figure 5.12 Arial View of Olushandja Dam 5-15 Figure 5.13 North and South Walls of the Olushandja Dam 5-16 Figure 5.14 Storage and Surface Area Curves of Olushandja Dam (NamWater, 2004) 5-17 Figure 5.15 Start of the Etaka Canal at the South Wall of the Olushandja Dam 5-18 Figure 5.16 Location and Type of Borehole Water Points in the Omusati Region (LCE, 2011) 5-23 Figure 5.17 Location and Type of Borehole Water Points in the Ohangwena and Oshikoto Regions (LCE, 2011) 5-23 Figure 6.1 Monthly Water Consumption for the Whole Cuvelai Area, Excluding Irrigation 6-2 Figure 6.2 Distribution of Monthly Sales Volumes as a Percentage of Total Volume for the Cuvelai Area, Excluding Irrigation 6-3 Figure 6.3 Annual Sales Volumes for the Whole Cuvelai Area, Excluding Irrigation 6-4 Figure 6.4 Proportion of Sales Volumes per Consumption Category, Excluding Irrigation (Percentage of the Total) 6-5 Figure 6.5 Annual Sales Volumes to Ministerial Customers in the Cuvelai Area 6-8 Figure 6.6 Annual Urban and Rural Water Sales for the Cuvelai Area (Mm3/a) 6-10 Figure 6.7 Total Irrigation Water Use in the Cuvelai Area (Mm3/a) 6-11 Figure 6.8 Total Number of Billed Consumers per Month in the Cuvelai Area 6-13 Figure 6.9 Average Annual Number of Billed Consumers per Category in the Cuvelai Area 6-14 Figure 6.10 Monthly Abstraction at Calueque (Mm3/m) 6-15 Figure 6.11 Comparison of Annual Inflow into- and Consumption Volumes in the Cuvelai Area 6-16 Figure 6.12 Relationship between the Proportion of the Non-Revenue Water and the Total Consumption Values, Including and Excluding Irrigation Consumption 6-17
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FIGURES (continued)
Figure 7.1 Water Supply Zones of the Cuvelai Area 7-2 Figure 7.2 Constant Growth Rates Applied to Population of the Four Northern Regions 7-5 Figure 7.3 Growth Rate Illustration Number 1: Constant Growth Rates 7-6 Figure 7.4 Growth Rate Illustration Number 2: Variable Growth Rates 7-7 Figure 7.5 Growth Rate Illustration Number 3: Variable Growth Rates 7-8 Figure 7.6 Supply Area 2 for the Ruacana South Rural Water Supply Project 7-10 Figure 7.7 King Kauluma Rural Water Supply Project 7-11 Figure 7.8 Urban Sales and Water Demand Projections for the Cuvelai Area 7-16 Figure 7.9 Rural Sales and Water Demand Projections for the Cuvelai Area 7-25 Figure 7.10 Combined Sales and Water Demand Projections for the Cuvelai Area 7-26 Figure 7.11 Historical Consumption and Theoretical Demands for Irrigation Use 7-28 Figure 7.12 Overall Historical Consumption and Theoretical Demands for the Project 7-29 Figure 7.13 Historic and Estimated Abstraction Requirements for the Cuvelai Area 7-34 Figure 7.1 Water Supply Zones of the Cuvelai Area 7-2 Figure 7.2 Constant Growth Rates Applied to Population of the Four Northern Regions 7-5 Figure 7.3 Growth Rate Illustration Number 1: Constant Growth Rates 7-6 Figure 7.4 Growth Rate Illustration Number 2: Variable Growth Rates 7-7 Figure 7.5 Growth Rate Illustration Number 3: Variable Growth Rates 7-8 Figure 7.6 Supply Area 2 for the Ruacana South Rural Water Supply Project 7-10 Figure 7.7 King Kauluma Rural Water Supply Project 7-11 Figure 7.8 Urban Sales and Water Demand Projections for the Cuvelai Area 7-16 Figure 7.9 Rural Sales and Water Demand Projections for the Cuvelai Area 7-25 Figure 7.10 Combined Sales and Water Demand Projections for the Cuvelai Area 7-26 Figure 7.11 Historical Consumption and Theoretical Demands for Irrigation Use 7-28 Figure 7.12 Overall Historical Consumption and Theoretical Demands for the Project 7-29 Figure 7.13 Historic and Estimated Abstraction Requirements for the Cuvelai Area 7-34 Figure 7.1 Water Supply Zones of the Cuvelai Area 7-2 Figure 7.2 Constant Growth Rates Applied to Population of the Four Northern Regions 7-5 Figure 7.3 Growth Rate Illustration Number 1: Constant Growth Rates 7-6
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ABBREVIATIONS amsl Above Mean Sea Level AIDS Acquired Immunodeficiency Syndrome ART Anti-Retroviral Therapy bgl Below Ground Level BGR Bundenstalt für Geowissenschaften und Rohstoffe (German Federal Institute for Geosciences and Natural Resources) BOOT Build, Own, Operate and Transfer BWMP Bulk Water Master Plan c Capita ca Circa (approximately) CAJVC Central Area Joint Venture Consultants CAN Central Area of Namibia CAWMP Central Area Water Master Plan CBS Central Bureau of Statistics CEB Cuvelai-Etosha Basin CENORED Central Regional Electricity Distributor CNWSA Central North Water Supply Area (alternative term for the area of the Cuvelai supplied by NamWater’s pipeline and canal infrastructure) CoW City of Windhoek CRRWSDP Combined Regional Rural Water Supply Development Plan CSU Colorado State University CWSA Central Water Supply Area (alternative term for the Central Area of Namibia supplied by the ENWC and downstream schemes) DO Otavi Dolomite Aquifer DOA Auros, Gauss and Berg Aukas Formations DPC Dynamic Prime Cost DRM Directorate of Resource Management DRWS Directorate of Rural Water Supply (now the DWSSC) DWA Department of Water Affairs DWAF Department of Water Affairs and Forestry DWSSC Directorate of Water Supply and Sanitation Coordination (previously the DRWS) ENVES Environmental Engineering Services CC ENWC Eastern National Water Carrier, also the Grootfontein – Omakato, Canal EoI Expression of Interest EPA Environmental Protection Agency (United States Government) EPSMO Environmental Protection and Sustainable Management of the Okavango River Basin FSL Full Supply Level GDP Gross Domestic Product GRN Government of the Republic of Namibia GROWAS Groundwater Database GRP Glass Reinforced Plastic (pipes)
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ABBREVIATIONS (continued)
GTZ Gesellschaft für Technische Zusammenarbeit (German Technical Cooperation) ha Hectare ha/LSU Hectare per Large Stock Unit HIV Human Immunodeficiency Virus Hz Hertz IAEA International Atomic Energy Association IFA Integrated Flow Assessment IPPR Institute for Public Policy Research IWRM Integrated Water Resources Management IWRMP Integrated Water Resources Management Plan IWRMPJVN Integrated Water Resources Management Plan Joint Venture Namibia JVC Joint Venture Consultants km Kilometre km2 Square kilometre km3 Cubic kilometre KEL Etosha Limestone Aquifer KfW Kreditanstalt für Wiederaufbau (Reconstruction Credit Institute, a German government-owned development bank KOH Ohangwena Multi-layered Aquifer KOM Omusati Multi-zoned Aquifer KOS Oshana Multi-layered Aquifer KOV Oshivelo Multi-layered Aquifer KTWSP Kunene Transboundary Water Supply Project KUNENERAK Kunene River Awareness Kit kg Kilogram kV Kilo Volt kVA Kilo Volt-Ampere kW Kilo Watt ℓ/c/d Litres per capita (person) per day ℓ/bed/d Litres per bed (hospital) per day ℓ/house/d Litres per household per day ℓ/LSU/d Litres per (equivalent) large stock unit per day ℓ/m2/d Litres per square metre per day ℓ/patient/d Litres per clinic outpatient per day (typically rural areas) ℓ/SSU/d Litres per (equivalent) small stock unit per day LCE Lund Consulting Engineers CC LSU Large Stock Unit (equivalent)
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ABBREVIATIONS (continued) masl Metres above sea level m Metre m2/d Square metres per day m3 Cubic metres m3/a Cubic metres per annum m3/d Cubic metres per day m3/h Cubic metres per hour m3/ha/a Cubic metres per hectare per annum m3/m Cubic metres per month m3/s Cubic metres per second (cumec) mg/ℓ Milligrams per litre (also parts per million) mm Millimetres mm/a Millimetres per annum mm/m Millimetres per month Mm3 Million cubic metres Mm3/a Million cubic metres per annum Ma Million years MAP Mean Annual Precipitation MAR Managed Aquifer Recharge also Mean Annual Runoff MAWF Ministry of Agriculture, Water and Forestry (previously the MAWRD) MAWRD Ministry of Agriculture, Water and Rural Development (now the MAWF) MFMR Ministry of Fisheries and Marine Resources MHAI Ministry of Home Affairs and Immigration MHSS Ministry of Health and Social Services MLR Ministry of Lands and Resettlement MME Ministry of Mines and Energy MoD Ministry of Defence MoE Ministry of Education MRCE Manfred Redecker Consulting Engineer MRLGHRD Ministry of Ministry of Regional, Local Government and Housing and Rural Development MSS Ministry of Safety and Security MW Mega Watts NamPower Namibia Power Corporation (previously SWAWEK) NamWater Namibia Water Corporation Ltd NDP National Development Plan NDP3 3rd National Development Plan NDP4 4th National Development Plan NEPRU Namibian Economic Policy Research Unit NHIES Namibia Household Income and Expenditure Survey NPC National Planning Commission NRW Non-Revenue Water
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ABBREVIATIONS (continued)
NSA Namibia Statistics Agency NTU Nephelometric Turbidity Units NWQG Namibia Water Quality Guidelines NWQS Namibia Water Quality Standard ODA Otavi Dolomite Aquifer OKACOM Permanent Okavango River Basin Water Commission OOTP Office of the President ORASECOM Orange Senqu River Commission PI Pacific Institute PJTC Permanent Joint Technical Commission PLC Programmable Logic Controller also Public Limited Company PMCC Pedro Maritz Civil Consultant PSC Project Steering Committee rpm Revolutions Per Minute RAISON Research and Information Services of Namibia RWSIDP Regional Strategic Water Infrastructure Development Programme SAIEA Southern African Institute for Environmental Assessment SADC Southern African Development Community SCE Seelenbinder Consulting Engineers CC SSU Small Stock Unit TDS Total Dissolved Solids TEM Transient Electro-Magnetic TIDI Tianjin Investigation, Design and Research Institute ToR Terms of Reference UDA Urban Dynamics Africa UNDP United Nations Development Programme VM Virtual Marketing WHO World Health Organisation WMARS Windhoek Managed Aquifer Recharge Scheme WDM Water Demand Management WMARS Windhoek Managed Aquifer Recharge Scheme WTC Water Transfer Consultants $ Namibian Dollar
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GLOSSARY OF TERMS
Alluvium Sediments deposited by flowing rivers.
Aquiclude A solid, impermeable area underlying or overlying an aquifer through which virtually no water flows.
Aquitard A bed of low permeability along an aquifer, or a zone within the earth that restricts the flow of groundwater from one aquifer to another.
Aquifer An aquifer is an underground layer of water-bearing permeable rock or unconsolidated materials (gravel, sand, or silt) from which groundwater can be extracted using a water well or borehole.
Aquifer, alluvial Aquifer consisting of alluvium or alluvial sediments, typically in the context of this Report, in an ephemeral river bed, for example in the Omaruru River.
Aquifer, confined An aquifer which is overlain by a confining bed which has a significantly lower hydraulic conductivity than the aquifer.
Aquifer, fractured Water is stored in cracks, fissures and fractures in otherwise solid rock.
Aquifer, unconfined An aquifer which does not feature a confining layer (an aquitard or aquiclude), where the water table is exposed to the atmosphere through openings in the overlying materials, often the shallowest aquifer at a given location.
Artesian well A well which derives its water from a confined aquifer in which the water level is above the ground surface, synonymous with flowing artesian well.
Artificial recharge The artificial enhancement or the recharge of an aquifer is a process where surface water runoff is impounded in a dam to allow the sediments and silt in the water to settle in the dam without the addition of chemicals. The clear water is decanted off and recharged into an aquifer by discharging the water into an infiltration pond over the aquifer, which enables the water to infiltrate into the ground and recharge the aquifer.
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GLOSSARY OF TERMS (continued)
CAN Central Area of Namibia, defined as that part of the country served with water by the Grootfontein – Omatako Eastern National Water Carrier (ENWC) canal and the 3-dam system consisting of the Omatako, Von Bach and Swakoppoort Dams.
Conventional water resources Surface water (rivers and dams) and groundwater sources.
Correlation coefficient The value of the correlation coefficient quantifies to what extent two variables or datasets follow the same variation. The value of the coefficient varies between +1.0, indicating perfect correlation, and -1.0, indicating a perfect negative correlation. A value of around zero would indicate that the two sets of data are not in any way related.
Cuvelai area Sometimes also referred to as NamWater’s Central North Water Supply Area (CNWSA), covers those portions of the Omusati, Oshana, Ohangwena and Oshikoto Regions supplied with water via the bulk (belonging to NamWater) and rural (belonging to the MAWF) pipeline networks.
Desalination The removal of salt (mostly sodium chloride) and other minerals from the sea water to make it suitable for human consumption and other uses in industry, manufacturing or mining.
Ephemeral river River which flows for a short period of time only following good rains.
Gini coefficient The Gini coefficient or index is a measure of statistical dispersion, which measures the inequality among values of a frequency distribution. It is commonly used to represent the income distribution of a nation’s residents. A Gini coefficient of zero expresses perfect equality (where everyone has the same income), whilst a coefficient of one expresses maximal inequality.
Groundwater Groundwater is water located beneath the earth's surface in soil pore spaces and in the fractures of rock formations.
Hydrogeology The study of water flow in aquifers and the characterisation of aquifers.
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GLOSSARY OF TERMS (continued)
Iishana Plural of oshana; shallow, seasonally inundated depressions or pans.
Inter-basin Transfer Inter-basin transfers or trans-basin diversions describe man-made conveyance schemes which move water from one river basin, where it is available, to another basin where it is less available, or could be better utilised for human and industrial development.
Karst aquifer Karst topography is a landscape formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterised by underground drainage systems with sinkholes, dolines, and caves, formed where the fractures in the rocks have been enlarged by the chemical solution of the rock in the water percolating through the aquifer system. The main example in Namibia is the Grootfontein-Tsumeb-Otavi Mountain Land area.
Oshana Shallow, seasonally inundated depression or pan.
Perched aquifer Groundwater which accumulates above a low-permeability unit or strata, such as a clay layer. This term is generally used to refer to a small local area of groundwater (smaller than an unconfined aquifer) that occurs at an elevation higher than a regionally extensive aquifer.
Perennial river River which flows continuously all year.
Reclamation (water) The reclamation of domestic sewage water is the treatment of this effluent to potable water quality standards for direct reuse as potable water.
Recycling (water) The recycling of industrial wastewater is the reuse of water in the same industrial or mining process without any further treatment, for example by recycling water from slimes or tailings dams.
Reuse, direct The treatment of wastewater and the distribution thereof for consumption. This could be via a dual pipe system for irrigation purposes (sports grounds, golf courses, parks and gardens), or could be the augmentation of potable supply or direct groundwater recharge.
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GLOSSARY OF TERMS (continued)
Reuse, indirect The discharge of treated wastewater to the environment in a surface stream for reuse downstream, for ecosystem maintenance and / or for recreation.
Storativity, storage coefficient Also called storage coefficient, this is one of the physical properties which characterise the capacity of an aquifer to release groundwater. This is the volume of water an aquifer releases from or takes into storage per unit surface area of the aquifer per unit change in hydraulic head. This is equal to the product of specific storage and the aquifer thickness. In an unconfined aquifer, the storativity is equivalent to the specific yield.
Transmissivity The rate at which groundwater flows horizontally through an aquifer. The more transmissive the aquifer is in the area around production boreholes, the greater the volume of water that can be abstracted from storage.
Unconventional water resources Water resources other than surface water (rivers and dams) and groundwater sources, for example recycled water and desalinated sea water.
Water banking Water banking in an aquifer is a process where raw water in a dam is abstracted and treated in a conventional water purification plant before the water is mechanically injected into the aquifer. The major difference between water banking and artificial recharge is that the latter is based on natural processes such as the settling of silt and the infiltration of water into the ground.
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REFERENCES
Asano and Bahri, 2011: “Global Challenges to Wastewater Reclamation and Reuse”, by Prof. T. Asano and Dr. A. Bahri, On the Water Front, World Water Week, 2011.
Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), 2013: “Groundwater Investigation in the Cuvelai-Etosha Basin (CEB): Information Meeting Eenhana April 2013 Presentation”, Presentation by the BGR in collaboration with the Department of Water Affairs and Forestry, April 2013.
Central Area Joint Venture Consultants (CAJVC), 2004a: “Feasibility Study on Water Augmentation to the Central Area of Namibia: Volume 1: Summary Report”, Report for NamWater, Report No. NWPC-IP-TSUM97-01, by Central Areas Joint Venture Consultants, Windhoek, December 2004.
CAJVC, 2004b: “Feasibility Study on Water Augmentation to the Central Area of Namibia: Volume 2: Water Sources, Existing Supply Schemes and Updating of the Central Area Model”, Report for NamWater, Report No. NWPC-IP-TSUM97-01, by Central Areas Joint Venture Consultants, Windhoek, December 2004.
CAJVC, 2004c: “Feasibility Study on Water Augmentation to the Central Area of Namibia: Volume 3: Water Demand and Water Demand Management”, Report for NamWater, Report No. NWPC-IP-TSUM97-01, by Central Areas Joint Venture Consultants, Windhoek, December 2004.
CAJVC, 2004d: “Feasibility Study on Water Augmentation to the Central Area of Namibia: Volume 4: Water Quality and Environmental Impact Identification”, Report for NamWater, Report No. NWPC-IP-TSUM97-01, by Central Areas Joint Venture Consultants, Windhoek, December 2004.
Central Bureau of Statistics (CBS), 2006: “Namibia Household Income and Expenditure Survey (NHIES) 2003/2004”, Central Bureau of Statistics, National Planning Commission, Private Bag 13356, Windhoek, November, 2006.
Claassen and Page, 1978: “Ontwikkelingsplan vir Owambo”, ISBN 0 908 422 47 7, by P. E. Claassen and D. Page, Instituut vir Beplanningsnavorsing, Universiteit van Stellenbosch, Stellenbosch, 1978
Colorado State University (CSU) Extension, 2010: “Nitrates in Drinking Water”, Fact Sheet No. 0.517, 7/95, Revised 2010/08.
Director of Water Affairs (DWA), 1968: “Owamboland Master Water Plan”, prepared for the Director of Water Affairs, South West Africa Administration, Water Affairs Branch, Windhoek, September 1968.
Table of Contents xxi THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
REFERENCES (continued)
Department of Water Affairs (DWA), 1990: “Views and Recommendations to Improve the Rural Water Supply in the Cuvelai Drainage Basin in the Owambo Region”, Report for the Department of Water Affairs by Horst Kugele, Windhoek, November 1990.
DWA, 1991: “Regional Master Water Plan for the Owambo Region”, Report by the Planning Division of the Department of Water Affairs of the Ministry for Agriculture, Water and Rural Development, File No. 13/1/6/9, Report No. 2700/1/6/G, Windhoek, March 1991.
DWA, 1995: “Re-Evaluation of the Potential for Large Dams in the Cuvelai Delta”, Report by the Hydrology Division of the Department of Water Affairs of the Ministry for Agriculture, Water and Rural Development, File No. 11/4/3/1, Report No. 2700/3/1/H2, Windhoek, August 1995
DWA, 2001: “Groundwater in Namibia: An Explanation to the Hydrogeological Map”, publication which complements the Hydrogeological Map of Namibia, prepared as a Namibian – German technical cooperation project of the Department of Water Affairs, Ministry of Agriculture, Water and Rural Development, the Geological Survey of Namibia, Ministry of Mines and Energy, the Namibia Water Corporation and the Federal Institute for Geoscience and Natural Resources on behalf of the German Ministry of Economic Cooperation and Development, Windhoek, First Edition, December 2001.
Environmental Protection Agency (EPA), 2009: “National Primary Drinking Water Regulations”, United States Environmental Protection Agency, 816-F-09-004, May 2009.
Government of the Republic of Namibia (GRN), 2009, “Post Disaster Needs Assessment (PDNA): Floods 2009”, August 2009, by the GRN with support from the International Community.
Integrated Water Resources Management Plan Joint Venture Namibia (IWRMPJVN), 2010a: “Development of an Integrated Water Resources Management Plan for Namibia: Theme Report 1: Review and Assessment of Existing Situation”, Report for the Ministry of Agriculture, Water and Forestry, by Integrated Water Resources Management Plan Joint Venture (Windhoek Consulting Engineers, Environmental Engineering Services CC, Heyns International Water Consultancy, Environmental Evaluation Association of Namibia, Institute for Management and Leadership Training and Dynamic Water Resources Management, Windhoek, August 2010.
IWRMPJVN, 2010b: “Development of an Integrated Water Resources Management Plan for Namibia: Theme Report 2: The Assessment of Resource Potential and Development Needs”, Report for the Ministry of Agriculture, Water and Forestry, by Integrated Water Resources Management Plan Joint Venture (Windhoek Consulting Engineers, Environmental Engineering Services CC, Heyns International Water Consultancy, Environmental Evaluation Association of Namibia, Institute for Management and Leadership Training and Dynamic Water Resources Management, Windhoek, August 2010.
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REFERENCES (continued)
Joint Venture Consultants (JVC), 1993a: “Central Area Water Master Plan: Phase 1, Volume 1: Summary Report”, Report for the Ministry of Agriculture, Water and Rural Development (Department of Water Affairs), Report No. DIR/1/93/1, by Joint Venture Consultants (Consulting Engineers Salzgitter, Lund Consulting Engineers and Windhoek Consulting Engineers), Windhoek, July 1993.
Joint Venture Consultants (JVC), 1994: “Feasibility Study for the Development of Water Supply for the Area Between Katima Mulilo and Kongola in the Eastern Caprivi”, Report for the Ministry of Agriculture, Water and Rural Development (Department of Water Affairs), File No. 16/6/1/2, Report No. 2300/6/1/2/PI, by Joint Venture Consultants (Consulting Engineers Salzgitter and Lund Consulting Engineers), Windhoek, October 1994.
Kunene River Awareness Kit, KUNENERAK: An information and knowledge management tool for the Kunene River basin, and a PJTC initiative: http://www.kunenerak.org/
Liebenberg 2009, “Technical Report on Irrigation Development in the Namibia Section of the Okavango River Basin”, Report for the Permanent Okavango River Basin Water Commission (OKACOM), by P. J. Liebenberg, Maun, Botswana, June 2009.
Lund Consulting Engineers CC (LCE), 1992a: “Calueque Dam: Assurance of Water for Transfer to Owambo”, Feasibility Study Draft Report for the Ministry of Agriculture, Water and Rural Development, Ref. 192/1, prepared by Chunnet, Fourie and Partners for and in association with Lund Consulting Engineers, Windhoek, January 1992.
LCE 1992b, “Phase 2 of the Reinstatement of the Calueque – Olushandja Component of the Calueque Dam Water Supply Scheme”, Draft Planning Report, Volume 1: Report, Tables and Figures, Report for the Ministry of Agriculture, Water and Rural Development, File No. 14/4/1/7/2, 4/4/7/2/5, by Lund Consulting Engineers, Windhoek, February 1992.
LCE 1992c, “Phase 2 of the Reinstatement of the Calueque – Olushandja Component of the Calueque Dam Water Supply Scheme”, Planning Report, Report for the Ministry of Agriculture, Water and Rural Development, File No. 14/4/1/7/2, by Lund Consulting Engineers, Windhoek, June 1992.
LCE, 2004: “Feasibility Study on the Provision of Irrigation Off-takes from and Rehabilitation of the Calueque – Border Canal”, Report for the Namibia Water Corporation Ltd. (NamWater), Report No. C-CALOM00, by Lund Consulting Engineers CC, Windhoek, May 2004.
LCE, 2009: “Water Supply Infrastructure Development and Capital Replacement Master Water Plan for the Central North Water Supply Area”, Report for the Infrastructure Planning Division of the Namibia Water Corporation Ltd. (NamWater), Report No. NWC-IP-NZWW106, by Lund Consulting Engineers CC, Windhoek, September 2009.
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REFERENCES (continued)
LCE, 2011: “Combined Regional Rural Water Supply Development Plan for the Oshikoto, Ohangwena Oshana and Omusati Regions”, Report for the Ministry of Agriculture, Water and Forestry, by Lund Consulting Engineers CC, Final Report, Volume 1, Windhoek, December 2011.
Mendelsohn et al., 2000: “A profile of North – Central Namibia”, J. Mendelsohn, S. el Obeid and C. Roberts, ISBN 99916-0-215-1, produced by Environmental Profiles Project, Directorate of Environmental Affairs, Ministry of Environment and Tourism, Windhoek, Gamsberg Macmillan, 2000.
Mendelsohn et al., 2009: “Atlas of Namibia: A Portrait of the Land and its People”, J. Mendelsohn, A. Jarvis, C. Roberts and T. Robertson, ISBN 978-1-920289-16-4, Published for the Ministry of Environment and Tourism by Sunbird Publishers, Cape Town, South Africa, Third Edition 2009
Mendelsohn et al., 2013: “A Profile and Atlas of the Cuvelai – Etosha Basin”, J. Mendelsohn, A. Jarvis and T. Robertson, ISBN 978-99916-780-7-8, Published for the Sustainable Integrated Water Resources Management Project in the Cuvelai-Etosha Basin of the Ministry of Agriculture, Water and Forestry by John Meinert Printing, Windhoek 2013.
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NamWater, 2004: “Situation Assessment on Calueque Pump Station”, Report by the Infrastructure Planning Division of the Namibia Water Corporation Ltd (NamWater), Report No. NWC-IP-WRC0104-01, Windhoek, August 2004.
National Planning Commission (NPC), 2002: “2001 Population and Housing Census: Preliminary Report”, Census Office, National Planning Commission, ISBN 0-86976-571-X, Windhoek, March 2002.
NPC, 2006: “Population Projections 2001 – 2031: National and Regional Figures”, Central Bureau of Statistics, National Planning Commission, ISBN 0-86976-676-7, Windhoek, January 2006.
NPC, 2008: “Third National Development Plan (NDP3): 2007/08 – 2011/12, Volume 1: Executive Summary”, ISBN 978-0-869 76-778-8, Windhoek, 2008.
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REFERENCES (continued)
NPC, 2012: “Namibia 2011 Population and Housing Census: Preliminary Results”, National Planning Commission, ISBN 978-99945-0-051-2, Windhoek, April 2012.
NPC, NDP4: “Namibia’s Fourth National Development Plan: 2012/13 to 2016/17”, ISBN 978- 99945-0-055-0, Office of the President, National Planning Commission.
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NSA, 2012b: “Namibia Household Income and Expenditure Survey (NHIES) 2009/2010”, Namibia Statistics Agency, Windhoek, 2012.
Office of the President (OOTP), 2004: “Namibia Vision 2030: Policy Framework for Long-Term National Development”, ISBN 999916-56-04-9, published for the Office of the President by Namprint, Windhoek, 2004.
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Pallet, J. (Ed.) 1997: “Sharing Water in Southern Africa”, ISBN 99916-43-21-4, Desert Research Foundation of Namibia, Windhoek, 1997.
Pacific Institute (PI), undated: Water Rates: Water Demand Forecasts”, www.pacinst.org.
Pitman and Midgley, 1974: “Synthesised Monthly Flows in the Cunene River System”, Report for the Department of Water Affairs, South West Africa, Report No. 2/74, by W. V. Pitman and D. C. Midgley of the Hydrological Research Unit, University of the Witwatersrand, Johannesburg, March 1974.
Smith, 2011: “Overcoming Challenges in Wastewater Reuse: A Case Study of San Antonio, Texas”, by Tiziana Smith, Thesis in the Bachelor of Arts for the Committee on Degrees in Environmental Science and Public Policy, Harvard College, Cambridge, Massachusetts, March 2011.
Tianjin Investigation and Design Institute (TIDI), 1998: “Okavango River – Ohangwena/Oshikoto
Water Supply Pipeline Project: Preliminary Planning Report, (F66G-A2-1),: Volume 1: Summary Report”, Report by Tianjin Investigation and Design Institute for the Ministry of Water Resources, People’s Republic of China, January 1998.
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REFERENCES (continued)
Urban Dynamics Africa (UDA), 2006: “Integrated Land Use Plan for the four North Central Regions of Namibia”, Report by Urban Dynamics Africa, for the Ministry of Lands, Resettlement and Rehabilitation, Windhoek, August 2006.
Van der Merwe et al., 2013: “Securing Water Supply to Windhoek through Unconventional Water Resources”, B. F. van der Merwe, H. I. Peters, H. Drews, paper presented at the 9th International Water Association International Reuse Conference, Windhoek, October 2013.
Virtual Marketing (VM), 2010/11: “Who’s Who of Namibia: Engineering: 2010/2011”, published by Virtual Marketing, Windhoek.
Water Transfer Consultants (WTC), 1997a: “Feasibility Study on the Okavango River to Grootfontein Link of the Eastern National Water Carrier: Volume 1: Summary Report”, File Number 13/2/2/2, Report for the Ministry of Agriculture, Water and Rural Development (Department of Water Affairs), by Water Transfer Consultants (Bicon Namibia, Lund Consulting Engineers and Parkman), Windhoek, August 1997.
WTC, 1997b: “Feasibility Study on the Okavango River to Grootfontein Link of the Eastern National Water Carrier: Volume 2: Water Resources”, File Number 13/2/2/2, Report for the Ministry of Agriculture, Water and Rural Development (Department of Water Affairs), by Water Transfer Consultants (Bicon Namibia, Lund Consulting Engineers and Parkman), Windhoek, August 1997.
World Health Organisation (WHO), 2003: “Chloride in Drinking Water: Background Document for Development of WHO Guidelines for Drinking Water Quality”, WHO/SDE/WSH/03.04/03, World Health Organisation, 20 Avenue Appia, 1211 Geneva 27, Switzerland, 2003.
WHO, 2004: “Sulphate in Drinking Water: Background Document for Development of WHO Guidelines for Drinking Water Quality”, WHO/SDE/WSH/03.04/114, World Health Organisation, 20 Avenue Appia, 1211 Geneva 27, Switzerland,
WHO, 2011a: “Nitrate and Nitrite in Drinking Water: Background Document for Development of WHO Guidelines for Drinking Water Quality”, WHO/SDE/WSH/07.01/16/Rev/1, World Health Organisation, 20 Avenue Appia, 1211 Geneva 27, Switzerland, 2011.
WHO, 2011b: “Total Dissolved Solids in Drinking Water: Background Document for Development of WHO Guidelines for Drinking Water Quality”, WHO/SDE/WSH/03.04/16, World Health Organisation, 20 Avenue Appia, 1211 Geneva 27, Switzerland, 2011.
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INTRODUCTION
1.1 PROJECT BACKGROUND
1.1.1 Project Advertisement and Award In July 2011, the Ministry of Agriculture, Water and Forestry (MAWF) openly advertised for expressions of interest from all Namibian registered, reputable, experienced and qualified engineering consultancy firms to form a consortium of all necessary disciplines and submit an Expression of Interest for the feasibility study of the “Kavango Link to the Eastern National Water Carrier and to the Cuvelai Water Supply Scheme”.
In order to put together a consultancy team with the required capacity and expertise to successfully tackle a project of this nature, Lund Consulting Engineers CC and Seelenbinder Consulting Engineers CC formed a joint venture, into which several other experts, both individuals and companies, and incorporating engineering, environmental, legal, social and other expertise, were incorporated as sub-consultants. This consortium of experts submitted an Expression of Interest to the Ministry of Agriculture, Water and Forestry, which submission was evaluated by them and by NamWater, and which was ultimately successful. The Consultant was consequently appointed to prepare a Terms of Reference (ToR) document for the Consultancy Services for an envisaged Feasibility Study into the “Kavango Link to the Eastern National Water Carrier and to the Cuvelai Water Supply Scheme”.
During the process of preparing the Terms of Reference, the Ministry of Agriculture, Water and Forestry and NamWater agreed, that in order to comply with the Equator Principles and international best practice, the following changes would be made to the Project:
1. The environmental (and social) component (investigations and assessments) of the Study will be completely separate from the engineering component of the Study 2. Consequently independent consultancy teams will be appointed to work on these project components, 3. The first phase of this Project will be a desk study, pre-feasibility investigation into alternative water sources for the Cuvelai and Central Areas of Namibia, and 4. The title of the Project, at least for the first phase, will be changed to the following: “Augmentation of Water Supply to the Central Area of Namibia and the Cuvelai”, 5. The independent consultancy teams will report to a Project Steering Committee (PSC).
On this basis, the consortium prepared and, incorporating feedback from the MAWF and NamWater, finalised the ToR, which were submitted on 19 February 2013.
Following the submission of the Final Draft Terms of Reference, and in line with the altered project scope, the consortium which had submitted the Expression of Interest was split in two; the Engineering Consultancy / Consultant was separated from the Environmental and Social Consultancy / Consultant.
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These two teams both prepared Technical and Financial Inception Reports for their respective components of the Pre-Feasibility Study, which documents were submitted to the MAWF on 30 April 2013. The Technical Inception Reports set out the tasks and activities for the engineering and environmental and social components respectively, whilst the Financial Inception Reports contain the cost estimates associated with these tasks and activities.
These Inception Reports were evaluated by the PSC, which it had been agreed would consist of the MAWF, NamWater and the City of Windhoek, and feedback thereon was submitted to the Engineering and Environmental and Social Consultants for compilation and clarification. Project Meeting No. 4 between the PSC, the Engineering Consultant and the Environmental and Social Consultant was held on 24 July 2013 to discuss the various comments on these Inception Reports and to finalise and agree on the scope of services to be undertaken. The minutes of this meeting, containing these clarifications, form an addendum to the respective Technical Inception Reports.
The Technical and Financial Inception Reports, as clarified / amended were found acceptable, and following approval of the minutes of Project Meeting No. 4, the respective portions of the Pre-Feasibility Study: Augmentation of Water Supply to the Central Area of Namibia and the Cuvelai, were awarded to the Engineering Consultant and the Environmental and Social Consultant in August 2013.
1.1.2 Engineering, Environmental and Social Consultants and External Reviewers
1.1.2.1 Engineering Consultant The Engineering Consultant consisted of a joint venture between Lund Consulting Engineers CC (LCE) and Seelenbinder Consulting Engineers CC (SCE), incorporating the following firms as sub-consultants:
1. Environmental Engineering Services CC (ENVES), 2. Manfred Redecker Consulting Engineer (MRCE), 3. Pedro Maritz Civil Consultant (PMCC), 4. Professional Environmental Technologies CC, 5. Dynamic Water Resources Management, 6. The Maproom, and 7. AECOM (previously BKS).
The Engineering Consultant, being a purely engineering team, concentrated on the engineering, financial and other technical aspects of this Study.
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1.1.2.2 Environmental and Social Consultant and External Review The Environmental and Social Consultant was led by Sustainable Solutions Trust, incorporating the following firms and individuals:
1. Ashby Associates CC, 2. Dr. J. King, 3. Coleen Mannheimer, Associate Researcher, National Botanical Research Institute, 4. Research and Information Services of Namibia (RAISON), 5. Nakamhela Attorneys, 6. Design and Development Services.
The Southern African Institute for Environmental Assessment (SAIEA) will provide external review and evaluation of the environmental and social component of the Study.
This Environmental and Social Consultant has functioned independently from the Engineering Consultant, as the separation of the technical and environmental assessments is one of the key requirements of the Equator Principles.
1.1.2.3 Liaison and Information Sharing Although the Engineering and Environmental and Social Consultants have carried out their respective assessments independently, there has been liaison and information sharing between the two teams as and when required. Senior members of both Consultants have attended the regular progress meetings with the PSC.
1.2 PROJECT AREA
The initial water supply area for the Study consisted of the Central Area of Namibia (CAN) and the Cuvelai area, which latter area corresponds with the largest portion of the four north central regions, being the Omusati, Oshana, Ohangwena and Oshikoto Regions.
During the compilation of the ToR for this Study, it was decided that the area east of Okakarara as far as Gam, as well as Otjinene and the areas south to Rietfontein, including Okondjatu, Talismanis, Gam and Tsumkwe be included in the investigation, as well as the areas along the Okavango River upstream of Rundu and the areas along any proposed pipeline route from the Okavango River. It was furthermore agreed that other areas which experience water shortages from time to time such as Omaruru, Otjimbingwe; both urban and rural, including the resettlement farms included in the Otjimbingwe bulk supply, and Otjiwarongo, after local sources are fully developed, also be included in the Project Area.
The various portions of the Study Area are shown in Figure 1.1 below.
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Figure 1.1: Preliminary Extent of the Study Area
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1.2.1 The Central Area of Namibia
The CAN, which is sometimes also referred to as NamWater’s Central Water Supply Area, encompasses those areas supplied with water by the Eastern National Water Carrier (ENWC) Canal (refer to Figure 1.2).
Figure 1.2: Schematic Layout of the Bulk Water Supply Infrastructure in the CAN
Okavango River Previously envisaged Kavango Link to the ENWC
Local Boreholes
Brandberg
Berg Aukas
Karst Aquifer including Grootfontein Goblenz Kombat Raw Water Reservoir
Grootfontein-Omatako Canal Central Reservoir
Okakarara & WTP
Navachab Mine Reservoir Omatako Dam Base Pump Station
Booster Pump Station
Okahandja Karibib WTP Otakarru Reservoir Gross Barmen OkangavaOkongava Okahandja ReservoirReservoir Boreholes
Von Bach Dam & Water Treatment Plant (WTP)
Swakoppoort Dam & Booster Pump Stns Base Pump Station Otjihase Mine
Goreangab Reclamation Windhoek Bulk Reservoir
Hosea Kutako Airport
Seeis Aquifer Windhoek Windhoek Aquifer
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The CAN is supplied with water from dams constructed on ephemeral rivers, groundwater sources mostly in the Karst areas and from reclaimed domestic effluent (in Windhoek only).
The groundwater abstracted in the Karst areas is delivered into the ENWC canal, through which it gravitates to Omatako Dam, from where it is pumped to Von Bach Dam. Water drawn from the Von Bach Dam is purified and transferred to Windhoek as well as to Otjihase Mine and the Windhoek International Airport. Water which enters Swakoppoort Dam is pumped westwards to Karibib and the Navachab Mine where it is respectively purified according to its intended use, and is also pumped eastwards to Von Bach Dam for eventual transfer to Windhoek.
1.2.2 The Cuvelai Area of Namibia
In the Cuvelai area, which is sometimes also referred to as NamWater’s Central North Water Supply Area (CNWSA) covers those portions of the Omusati, Oshana, Ohangwena and Oshikoto Regions supplied with water via the bulk (belonging to NamWater) and rural (belonging to the MAWF) pipeline networks. Areas to the west and east of the central pipeline network of the Cuvelai are supplied with groundwater via individual borehole installations. The water supply infrastructure in the Cuvelai is shown in Figure 1.3.
Figure 1.3: Layout of the Water Supply Infrastructure in the Cuvelai Area
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The water supplied via the pipeline network in the Cuvelai area is drawn from Calueque Dam, which is situated in Angola, some 30 km upstream of the Ruacana Falls and 15 km north of the Namibian – Angolan Border, under an abstraction agreement between the Namibian and Angolan Governments which dates back to 1969.
This water is pumped a short distance, after which it gravitates into Namibia via the Calueque – Oshakati Canal, after which some water is drawn off to supply the Etunda Irrigation Scheme. The remainder of the water gravitates past Olushandja Dam towards Oshakati via the canal, where it is purified for distribution to the north, south and east. Water drawn from the canal between Olushandja and Oshakati is also treated at Olushandja, Outapi (Ombalantu) and Ogongo prior to further distribution. Water is drawn from the canal into Olushandja Dam for emergency storage only.
Bulk water supply is the responsibility of NamWater as a State-owned enterprise, whilst the development of infrastructure in rural areas is done by the MAWF, Directorate of Water Supply and Sanitation Coordination (DWSSC). Upon completion, infrastructure developed by the DWSSC is often handed over to NamWater for operation and maintenance, possibly also ownsership, under an agreement between the parties.
1.3 PROJECT OBJECTIVE
The main objective of this Study was to examine all the nominally feasible options for securing the long term, up to 2050, water supply to the Central Area of Namibia (CAN) and the Cuvelai area of Namibia where existing sources might become inadequate in the near future.
1.4 OVERALL PROJECT APPROACH AND METHODOLOGY
1.4.1 Overall Project Methodology
The overall methodology followed with the execution of this Study was the following:
1. Analysis and confirmation of the Project Area, including which areas of the Central Area of Namibia (CAN) and the Cuvelai are to be served for back-up and / or for augmentation purposes, 2. Determination of the realistic water demands for the Project Area, being the following areas initially included in the Project Area (later confirmed): a. The CAN, b. The Cuvelai area, c. The Eastern Otjozondjupa and Omaheke Regions, d. Other areas which experience water shortages from time to time such as Omaruru, Otjimbingwe; both urban and rural, including the resettlement farms included in the Otjimbingwe bulk supply, Otjiwarongo, after local sources are fully developed, Otjinene, Okondjatu, Talismanis, Rietfontein, Gam and Tsumkwe, 3. Analysis of the potential savings or reductions in water demands which can be realised from intensified water demand measures (realistic water demands),
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4. Updating and confirming the capacities of the various currently available water supply sources, 5. A comparison of the water demands to be met over the planning horizon with the capacities of existing water supply sources in order to determine the expected extent and timing of supply shortfalls, 6. Establishing as far as possible the expected or potential capacities of future and / or additional water supply sources, 7. A comparison of the expected shortfalls (using current supply sources) with the expected capacities of additional water supply sources in order to determine which additional or combination of additional water supply sources are suitable and will be required in the future, 8. Preparing concept configurations and cost estimates for supply schemes to develop the suitable future or additional water supply sources, 9. Preparing financial analyses for the most feasible future / additional supply schemes up to the level of Dynamic Prime Cost (DPC), 10. Providing the technical information to the environmental / social team in order for them to assess the likely environmental impacts and costs of the various options considered, 11. Considering the results of the financial analyses of the proposed future schemes, the environmental impacts and costs as well as other considerations, to select the overall optimum or best trade-off (most financially viable, economically beneficial and environmentally acceptable) future water supply schemes which are to be investigated in further detail in a following stage of this overall Project.
1.4.2 Underlying Approach to this Study The underlying approach approved for this Pre-Feasibility Study, was that of a desk study which used the information which is available from whatever sources, in particular that from previous studies, updating this information where required, in order to arrive at an up to date and relevant pre-feasibility investigation. It was envisaged that major field work, associated components and more detailed investigations will only become necessary in a later, detailed feasibility or design phase, should the decision be made to proceed with the Project.
1.4.3 Planning Horizon
A planning horizon is the time frame for planning strategic activities and for accomplishing strategic goals, which means that establishing a planning horizon is a strategic decision for an organisation or agency.
NamWater assumed a 15 year planning period for the compilation of their Bulk Water Infrastructure Development and Capital Replacement Master Plans, under which water demand projections were prepared and supply sufficiencies analysed up to 2029/30. For rural water supply projects planned and implemented by the MAWF, a 15-year planning horizon is also usually applied.
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This Study however examines options which are of a strategic nature, with the aim of securing water supplies to the CAN and the Cuvelai for the medium to long term. Such projects typically have a long implementation period (up to 10 years) which should also be taken into account. The recent Master Plan for the Central Water Supply Area (the CAN) completed for NamWater determined that a new water source for the CAN is expected to become a necessity by 2020.
This is therefore the proposed implementation / commission date of the recommended project infrastructure, following which a sufficiency period of 30 years (for the supply of water and the minimum lifespan of infrastructure) should be used for the Study.
Water demands will therefore be prepared up to 2050 and all water supply options will be examined for supply sufficiency up to this date.
1.4.4 Client Liaison
The MAWF served as the principal Client for the purposes of this Study. In particular, the Engineering Consultant (as well as the Environmental and Social Consultant) reported to the Director in the Directorate of Resources Management in the MAWF.
In terms of technical matters, the Engineering Consultant however liaised with the PSC which was formed between designated officials from the MAWF, NamWater and the CoW and kept them informed on the progress of the Study.
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OVERVIEW OF NAMIBIA
2.1 OVERVIEW OF NAMIBIA
Namibia is the second largest country in Southern Africa, behind South Africa, and is situated roughly between 17° and 29° South of the equator and lies along the south-western coast of the African continent. The country is bounded by Angola and Zambia to the north, Zimbabwe and Botswana to the east, and by South Africa to the east and south. The western, coastal, border with the Atlantic Ocean is some 1,570 km long between the mouth of the Orange River in the south and that of the Kunene River in the north. Namibia covers an area of some 823,680 km2 and spans 1,320 km at its longest, 350 km at its narrowest and 1,440 km at its widest points (after Mendelsohn et al., 2009) and is home to some 2.1 million inhabitants (NPC, 2012).
2.2 CLIMATE AND GEOLOGY 2.2.1 The Climatic Systems of Southern Africa
An accurate understanding of Namibia’s climate as well as the interaction between climatic and physical determinants is essential for sustainable planning and management of the water sector (IWRMPJVN, 2010b).
Namibia’s climate is governed by its location on the south-western side of the African continent in the Subtropical High Pressure Zone between the Inter-Tropical Convergence Zone to the north and the Temperate Zone to the south. The Inter-Tropical Convergence Zone which straddles the equator is an area of intense weather activity where moist air, much of it carried by winds off the Indian and Atlantic Oceans, converges in a zone of low pressure. The warm, moist air rises, cools and condenses to form water vapour at higher altitudes, forming giant cloud masses which produce large amounts of rain in the tropics (after Mendelsohn et al., 2009). The movement of the Inter-Tropical Convergence Zone is caused by the convergence of the northeast and southeast trade winds.
The Temperate Zone wraps the bottom part of the earth in another broad band of moist air. Prevailing westerly winds carry a succession of low pressure systems and cold fronts from west to east in this zone. These systems originate as bursts of cold air from the Antarctic and many of these cold fronts sweep across southern Africa in winter (Mendelsohn et al., 2009).
In between the Inter-Tropical Convergence and the Temperate Zones lies the Subtropical High Pressure Zone in which Namibia is located. Quasi-stationary cells of high pressure dominate this broad area and two of these cells, the Botswana Anticyclone and the South Atlantic Cyclone, are what make Namibia’s climate so dry. The Botswana Anticyclone, which is prominent in winter, feeds dry air over Namibia and obstructs the flow of moist in from the Inter- Tropical Convergence Zone to the north. This gives rise to clear skies and warm to hot temperatures and this cell is the original cause of the Kalahari Desert and the surrounding arid and semi-arid areas.
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The South Atlantic cyclone blows cool air onto the coast from the south west, and has been in place a long time. This mechanism is the reason why there is a sea of sand in the Namib, as these strong winds have blown sand from the shore inland over millions of years (after Mendelsohn et al., 2009 and IWRMPJVN, 2010b).
The different seasons experienced in Namibia are driven by the northward and southward movement of these zones, in response to the apparent movements of the sun. The movement of the Inter-Tropical Convergence Zone south during the Namibian summer results in the rainfall season, normally starting in October and ending in April. In the far south, the Temperate Zone moves northwards during the Namibian winter, resulting in the winter rains which occur in the far southwest of the country. Small variations in the timing of these movements result in the considerable differences in the weather experienced in Namibia from one year to the next (IWRMPJVN, 2010b).
2.2.2 The Köppen-Geiger Climate Classification The Köppen Climate Classification is a widely used climate classification system, which was first published by the Russian-German climatologist Wladimir Köppen in 1884. Köppen himself later modified the system in 1918 and 1936, after which the German climatologist Rudolf Geiger collaborated with Köppen in making changes to the classification system, which is thus referred to as the Köppen-Geiger Climate Classification. This system is based on the concept that native vegetation is the best expression of climate. Climate zone boundaries have therefore been selected with vegetation distribution in mind, combined with average annual and monthly temperatures and precipitation and the seasonality of precipitation. This system divides climates across the world into five main groups, each with several types and subtypes.
Group A climates are tropical climates, Group B are dry (arid and semi-arid) climates, Group C are mild temperate climates, Group D are continental / microthermal climates and Group E are polar climates.
From Figure 2.1 it can be seen that Namibia is classified as being in Group B, which contains dry, arid and semi-arid climates, which are characterised by the actual precipitation being less than a threshold value set equal to the potential evapotranspiration. The sub-classifications in Group B which cover almost equal areas of Namibia are warm desert climate (BWh) and warm semi-arid climate (Bsh). The south western coastal belt is classified as being a cold desert climate (Bwk).
The majority of the southern and coastal areas of Namibia classified as a hot desert climate (BWh), which describes areas which loose more water via evapotranspiration than falls in precipitation. Hot desert climates are typically found in subtropical areas, and feature unbroken sunshine for most of the year due to stable descending air and high pressure (refer above).
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Figure 2.1: Köppen-Geiger Climate Classification for Africa (Wikipedia)
The coastal belt in the southwest of the country, from the mouth of the Orange River northwards, is classified as a cold desert climate (Bwk), which is a variant of the hot desert climate, due to the coastal location. This area is characterised by cooler temperatures than are encountered elsewhere at comparable latitudes due to the presence of cold ocean currents, onshore winds and frequent fog and low clouds. Nevertheless, these places rank amongst the driest on earth in terms of precipitation received.
The majority of the northern and eastern parts of Namibia are classified as a hot semi-arid or steppe climate (BSh), which describes areas with precipitation values below the potential evapotranspiration rates. In terms of ecological characteristics and agricultural potential, these areas are intermediate between desert climates and humid climates. Hot semi-arid areas tend to be located in the tropics and subtropics and are most commonly found around the fringes of subtropical deserts.
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2.2.3 Rainfall
Namibia is the most arid country in Southern Africa, with the driest climate in Africa south of the Sahara (JVC, 1993a), where it is estimated that only about 2% of the rainfall ends up as surface run-off and a mere 1% becomes available to recharge the groundwater (IWRMPJVN, 2010a). Rainfall and evaporation data for selected Southern African Development Community (SADC) countries are shown in Table 2.1.
Table 2.1: Rainfall and Evaporation Data for Selected SADC Countries (Pallet, 1997)
Potential Total Surface Runoff Average Rainfall Range Evaporation Country Rainfall (mm/a) Range (mm) (km2) (mm/a) (mm/a)
Angola 25 – 1,600 800 1,300 – 2,600 104 130.0
Botswana 250 – 650 400 2,600 – 3,700 0.6 0.35 Lesotho 500 – 2,000 700 1,800 – 2,100 136 4.13 Malawi 700 – 2,800 1,000 1,800 – 2,000 60 7.06 Mozambique 350 – 2,000 1,100 1,100 – 2,000 275 220.0 Namibia 10 – 700 250 2,600 – 3,700 1.5 1.24 South Africa 50 – 3,000 500 1,100 – 3,000 39 47.45 Swaziland 500 – 1,500 800 2,000 – 2,200 111 1.94 Tanzania 300 – 1,600 750 1,100 – 2,000 78 74.0 Zambia 700 – 1,200 800 2,000 – 2,500 133 100.0 Zimbabwe 350 – 1,000 700 2,000 – 2,600 34 13.1
Rainfall in Namibia is low, unpredictable, unreliable, erratic and spatially unevenly distributed across the country (IWRMPJVN, 2010a). The variability of rainfall is such that the total rainfalls in one year are often several times greater than the falls in other years (Mendelsohn et al., 2009). The spatial variation is such that the Zambezi (Caprivi) Region in the extreme north east has a Mean Annual Precipitation (MAP) of over 600 mm/a, which decreases to the south and west, such that the Namib Desert receives less than 50 mm/a on average. The country-wide average rainfall is approximately 272 mm (IWRMPJVN, 2010a).
However, although average rainfall is a widely used measure, the median rainfall is a better reflection of “normal” rainfall, since averages are easily exaggerated by very high falls (as experienced in 2010/11), whilst medians are not (after Mendelsohn et al., 2009).
The distribution of median rainfall is shown in Figure 2.2, from which it can be seen that even across the CAN and Cuvelai areas, rainfall varies widely. In the Cuvelai, rainfall, almost all of which falls in the summer months between November and April, generally increases from the west, where Ruacana has a median rainfall of about 350 mm per annum, to the east, where Okongo has a median rainfall in the order of 500 mm per annum. Rainfall is also generally more reliable in the eastern than in the western areas (after LCE, 2011). The area around Oshakati, with a median rainfall of 450 to 500 mm per annum, however receives slightly more rain than the immediately surrounding areas.
Chapter 2: Overview of Namibia 2-4 THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART I: THE CENTRAL AREA OF NAMIBIA
Figure 2.2: Median Annual Rainfall in Namibia (Mendelsohn et al., 2009)
Whilst the rainfall in the CAN follows a similar pattern to that of the Cuvelai (higher in the east than in the west), the variation is greater than that encountered in the Cuvelai: In the west, Karibib has a median rainfall of between 200 and 250 mm per annum, whilst in the north east, Grootfontein has a median rainfall in the region of 500 mm per annum. Windhoek has a median rainfall in the order of 300 to 350 mm per annum.
Figure 2.3 shows that with a coefficient of variation of greater than 40%, Namibia, together with the Sahara Desert, has the most variable rainfall in Africa. As a result, frequent shortages of rain are normal, whilst rainfall totals in some years may be several times greater than the amounts received in other years, as was the case in the 2010/11 rainy season (after Mendelsohn et al., 2009).
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Figure 2.3: Variation in Rainfall across Africa (Mendelsohn et al., 2009)
Figure 2.4: Variation in Rainfall across Namibia (Mendelsohn et al., 2009)
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Whilst on a continental scale, Namibia as a whole has the highest coefficient of variation in rainfall; mostly greater than 40%, on a national scale, this varies even more dramatically. The coefficient of variation (also the variation coefficient) of rainfall, shown in Figure 2.4, shows the extent of variability of rainfall relative to the mean or average on a national scale. Large portions of the CAN, including the eastern parts of the Omaheke and Otjozondjupa Regions, and the Cuvelai area have a coefficient of variation in the order of 30 to 40%. Variation in rainfall is higher in the western areas of both the CAN and the Cuvelai and in the extreme eastern portions of the Omaheke Region.
2.2.4 Temperature
Namibia is generally considered to be a hot country, although temperatures vary a great deal – during the day, from day to day, seasonally and over much longer periods. The highest temperature on official record was 43.5 C at Gobabeb on 21 February 1970 and the lowest was -10.5 C at Röhrbeck, north east of Mariental, on 02 August 1974. Average annual temperatures are generally lower along the west coast, increasing towards the interior and to the north, although higher altitudes make the central highlands cooler than would otherwise be expected. The central areas in the southern parts of Namibia are both the hottest, with the highest average maximum temperatures, and the coldest, with the lowest average minimum temperatures. The moderating effects of the coastal winds make the coast belt more temperate (Mendelsohn et al., 2009). The average daily temperature is 25 C and Namibia has an average of 10 hours of sunshine per day, though as with other climatic conditions, this varies greatly across the country (after JVC, 1933a).
2.2.5 Evaporation and Water Deficit Namibia’s low and variable rainfall is compounded by generally high rates of evaporation. Temperature, humidity, wind, vegetation and cloud cover all influence evaporation rates, which mean that these vary across the country. Whilst evaporation rates are generally high throughout, they are higher in the southern areas (more than 2,600 mm/a) than in the north eastern and coastal areas (less than 1,680 mm/a), due to higher cloud cover and cool and humid conditions respectively (refer to Figure 2.5) (after Mendelsohn et al., 2009).
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Figure 2.5: Average Annual Evaporation in Namibia (Mendelsohn et al., 2009)
The whole country potentially loses much more water through evaporation than it receives in rain. The water deficit, being the difference between the average annual rainfall and the average rate of evaporation, shown in Figure 2.6, however varies across the country. Water deficits are lower in the west and along the coast (1,700 – 1,900 mm/a), and are highest in a wide band extending from the south-east (where they are the highest in the country at over 2,500 mm/a) to the north-west, decreasing again to the north-east (less than 1,300 mm/a), as a result of higher rainfall and less evaporation.
The water deficit varies from about 1,700 mm/a to about 1,300 mm/a from west to east across the Cuvelai. The water deficit in the CAN is higher than that in the Cuvelai, varying from about 2,100 mm in the west near Karibib to about 1,500 mm/a in the Grootfontein area.
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Figure 2.6: Average Annual Water Deficit in Namibia (Mendelsohn et al., 2009)
2.2.6 Geology, Elevation, Relief and Soils
2.2.6.1 Geology1 Rock formations are clearly visible in many places in Namibia, which is due to the current arid environment which has produced little topsoil and vegetation to cover the underlying rocks. Namibia can be divided into two broad geological areas, one covering the western parts and the other the east parts. The western part of Namibia consists of a great variety of rock formations, most of them exposed in rugged landscapes of valleys, escarpments, mountains and large open plains. By contrast, the eastern part of Namibia is overlaid by sands and other sediments which were deposited much more recently. These landscapes are much more uniform, as the predominance of Kalahari sands on the surface means that there is much less variation from one area to another (after Mendelsohn et al., 2009).
1 The explanation of Namibia’s geology is extracted from “Groundwater in Namibia: An Explanation to the Hydrogeological Map”, DWA, 2001.
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Namibia’s varied geology encompasses rocks from the Archeaean to Cenozoic age, covering more than 2,600 million years (Ma) of the earth’s history. Nearly half of the country’s surface area is bedrock exposure, while the remainder is covered by the relatively younger, superficial deposits of the Kalahari and Namib Deserts (DWA, 2001).
Metamorphic inliers consisting of highly deformed gneisses, amphibolites, meta-sediments and associated intrusive rocks occur in the central and northern parts of the country, and represent some of the oldest rocks of Palaeoproterozoic age (ca. 2,200 to 1,800 Ma) in Namibia. The Kunene and Grootfontein Igneous Complexes in the north, the volcanic Orange River Group and the Vioolsdrif Suite in the south, as well as the volcano-sedimentary Khoabendus Group and Rehoboth Sequence also belong to this group.
The Mesoproterozoic (1,800 to 1,000 Ma) is represented by the Namaqua- land Metamorphic Complex, which comprises granitic gneisses, metasedimentary rocks and magmatic intrusions, and by the volcano-sedimentary Sinclair Sequence of central Namibia, with associated granites (e.g. Gamsberg Granite Suite).
The coastal and intra-continental arms of the Neoproterozoic Damara Orogen (800 to 500 Ma) underlie large parts of north-western and central Namibia, with platform carbonates in the north and a variety of meta-sedimentary rocks pointing to more variable depositional conditions further south. Along the south-western coast, the volcano-sedimentary Gariep Complex is interpreted as the southern extension of the Damara Orogen. During the later stages of orogenic evolution, the shallow-marine clastic sediments of the Nama Group, which covers much of central southern Namibia, were derived from the uplifted Damara and Gariep Belts.
Sedimentary and volcanic rocks of the Permian to Jurassic Karoo Sequence occur in the Aranos, Huab and Waterberg Basins, in the south-eastern and north-western parts of the country. They are extensively intruded by dolerite sills and dyke swarms, which in association with predominantly basaltic volcanism and a number of alkaline sub-volcanic intrusions, mark the break-up of Gondwanaland and the formation of the South Atlantic ocean during the Cretaceous period.
The currently last chapter of Namibia’s geological history is represented by the widespread Tertiary to recent (< 50 Ma) sediments of the Kalahari Sequence which cover large portions of the eastern part of the country (DWA, 2001).
The major geological divisions and groups of Namibia are shown in Figure 2.7 and the major rock types in Figure 2.8.
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Figure 2.7: Major Geological Divisions and Groups in Namibia (Mendelsohn et al., 2009)
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Figure 2.8: Rock Types in Namibia
2.2.6.2 Elevation and Relief Much of Namibia consists of a wide, rather flat plateau that continues north, south and east into Botswana and other neighbouring countries. The height of this plateau ranges between about 900 m and 1,300 m above sea level. There is however a great variation in altitude to the west and south, where the escarpment rises from the coast. The highest point in Namibia is the Brandberg, at 2,570 m above sea level, followed by Moltkeblick at 2,479 m above sea level in the Aus Mountains just south of Windhoek (Mendelsohn et al., 2009).
2.2.6.3 Soils As with rainfall, the Namibian soils vary greatly, both on a broad scale and in terms of a high degree of variability at a local level; from deep sands which are found in the Kalahari, to clayey and salty soils which are found in the Cuvelai (after Mendelsohn et al., 2009). As with the rainfall, the soils generally deteriorate in both quality and quantity from north east to south west with the notable exceptions being the rocky areas along the edge of the escarpment and the loose sediment cover of the Kalahari in the east (after JVC, 1993a). Most of Namibia’s soils however are unsuited to crop growth, although there are zones rated as having medium potential where moderately fertile soils cover between 20% and 50% of the area. Nevertheless, even those soils which area the most fertile in the Namibian context do not rate highly on a world scale of soil potential. These soils moreover occur in areas where rainfall is too low for rain-fed cultivation (after Mendelsohn et al., 2009).
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Figure 2.9: Dominant Soils in Namibia
2.3 POPULATION AND DEMOGRAPHICS 2.3.1 Namibia’s Population
Namibia’s population, estimated at 2.1 million inhabitants (NPC, 2012), is very unevenly spread across the country. Large areas of land are uninhabited and many others are very sparsely populated, whilst people are concentrated in towns and a few small rural areas.
In the Kavango Region, houses are clustered along the Okavango River and along the main roads, whilst areas in the interior of the region are more sparsely populated.
Largely as a consequence of the fertility of the soils and the availability of water in shallow hand-dug wells, the Cuvelai is much more densely populated than other rural areas in Namibia (after Mendelsohn et al., 2013). In fact, the north-central part of Namibia is the most densely populated part of the country, and contained 43% of the population in 2001 (NPC, 2002) and 40% of the population in 2011, on approximately 10% of the total area of Namibia (NPC, 2012). The population density in the Cuvelai area is highest in the central portion which is served by the pipeline network, decreasing gradually to the east and more abruptly to the west and south, largely as a consequence of the scarcity of water.
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Population density varies dramatically across the CAN, which generally has a low population density as large portions thereof are farmland. Inhabitants are concentrated in the main towns and cities, whilst the areas served by the pipeline network of the Waterberg Water Supply Area feature population densities higher than those of the surrounding areas, though not as high as in the Cuvelai. Due to the scarcity of water supplies, some areas in the eastern parts of the Omaheke and Otjozondjupa Regions are very sparsely populated.
Figure 2.10: Population Density across Namibia (Mendelsohn et al., 2009)
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2.3.2 Analysis of Population and Income Levels
The Gini coefficient1 for Namibia is 0.597 according to the results of the 2009/10 National Housing, Income and Expenditure Survey (NHIES) (NSA, 2012b). Although the inequality in the distribution in income decreased from 0.701 in 1993/94 and 0.604 in 2003/04 (CBS, 2006), it is still among the highest in the world. The poorest 30% of the households represent 41.7% of the population earning 9.3% of the income, whilst the highest 10% of the households represent 6.0% of the population earning 42.7% of the income (NSA, 2012b).
The 2003/04 NHIES determined that approximately 3.9% of the households spending more than 80% of their income on food were classified as severely poor and 23.9% were classified as poor, spending 60% to 79% of household income on food in Namibia, (CBS, 2006). With the 2009/10 NHIES, the definitions or poor and severely poor were changed from the use of the conventional food consumption ratio, as used with earlier surveys, to the use of a cost of basic needs approach. Monthly per capita poverty lines were determined, on which basis households considered poor and very poor were determined. Approximately 20% of households were found to be poor (a monthly per capita income of less than N$ 377.96 per person per month) and approximately 10% of households were found to be severely poor (a monthly per capita income of less than N$ 277.54 per person per month) (after NSA, 2012b).
There is a substantial disparity in poverty between rural and urban areas; 27% of rural households and regarded as poor versus 9.5% of urban households, whilst 13.6% of rural households are regarded as very poor, versus 4.4% of urban households (NSA, 2012b).
The regions with the highest percentage poor households are the Kavango2 (43.4%), Zambezi1 (41.7%), Oshikoto (33.9%) and Ohangwena (23.7%) Regions. In the Khomas and Erongo Regions, only 7.6% and 5.1% of the households respectively can be classified as poor according to this definition (after NSA, 2012b), as summarised in Table 2.2.
Consumption gives an indication of the expenditure of households. The results reveal the huge disparity between rural and urban areas, where the average annual consumption per capita in rural areas is N$ 7,841 compared with the N$ 23,592 in urban areas. Rural areas represent 57% of the households and 62% of the population, but they account for only 35% of the total consumption (NSA, 2012b).
1 The Gini coefficient or index is a measure of statistical dispersion, which measures the inequality among values of a frequency distribution. It is commonly used to represent the income distribution of a nation’s residents. A Gini coefficient of zero expresses perfect equality (where everyone has the same income), whilst a coefficient of one expresses maximal inequality.
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Table 2.2: 2009/10 Namibia Household Income and Expenditure Survey (NSA, 2012b)
Average Adjusted Population Poor in Household per Capita Consumption Region National Region Income per Income per per Capita (%) (%) Annum Annum (N$) (N$) (N$) Zambezi1 4.9 41.7 33,969 8,387 6,709 Erongo 9.0 5.1 84,989 27,079 22,702 Hardap 3.6 17.2 68,788 18,573 14,791 Karas 4.9 15.3 68,885 21,516 17,828 Kavango2 10.0 43.4 36,740 6,766 5,521 Khomas 19.1 7.6 132,209 36,238 31,173 Kunene 3.9 16.8 47,772 12,807 10,175 Ohangwena 8.9 23.7 46,622 9,162 7,295 Omaheke 3.5 20.9 56,289 15,940 12,491 Omusati 10.3 12.6 49,076 11,034 8,881 Oshana 8.0 13.5 65,445 15,482 12,938 Oshikoto 7.3 33.9 34,880 8,163 6,693 Otjozondjupa 6.4 22.9 60,108 17.006 13,194 Namibia 100 19.5 68,878 16,895 13,813 Urban 43.3 9.5 102,952 28,020 23,592 Rural 56.7 27.2 42,893 9,785 7,841 Notes: 1. Previously the Caprivi Region. 2. The Kavango Region before it was divided into the Kavango East and Kavango West Regions. These changes were made after the 2009/10 NHIES and the 2011 population census.
Based on family income a large percentage of households both in urban and rural areas cannot afford to pay the full cost for water services and may require a subsidy or cross subsidy to make water more affordable. If household income increases with the implementation of Vision 2030, the demand for water may increase substantially because of the income elasticity of demand (higher income families use more water on luxury consumption such as swimming pools, gardens and housing utensils than low income families).
2.3.3 The Effect of HIV/AIDS on Population Growth (UNDP Website 2014)
Namibia’s relatively small population of 2.1 million people has one of the highest HIV prevalence rates among pregnant women. Over the last 4 years, HIV prevalence rates within the general population have been estimated to be around 13.5%. Although the prevalence rate among pregnant women dropped from 22% in 2002 to 18.8% in 2010(2), the social and economic impacts of HIV and AIDS continue to be felt. The HIV and AIDS pandemic continues to pose a challenge due to its dynamic nature in the way it impacts on the Namibian population at large.
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By 2010, approximately 189,000 people were living with HIV. This number is predicted to increase to 201,000 in 2015/16. In 2010/11, approximately 9,300 people were newly infected with HIV with an estimated number of 25 new infections per day. Of the new infections in 2010, about 40 percent were among young people aged 15-24 and 68 percent of the new infections in this age group were among young women. The spread of HIV is further exacerbated by high unemployment rates, widespread poverty, prevalent sexual practices and high levels of violence against women and children. With about 2 to 3 babies being born HIV positive each day, HIV remains an important cause of infant and child mortality and reaching the virtual elimination target will require sustained efforts in promoting access to prevention commodities, treatment, care and support services.
Although Namibia has made remarkable progress in rolling out Anti-Retroviral Therapy (ART) services to those in need, the number of people who need treatment continues to increase from 99,700 in 2010/11 to 158,000 by 2015/16 (high bound estimates). The number of orphans and other vulnerable children registered with the Ministry of Gender Equality and Child Welfare has increased to around 140,000. Ultimately, AIDS-related illnesses remain the number one cause of death in Namibia. The epidemic has mainly affected the health, livelihoods and economic perspectives of many poor Namibians.
It is difficult or impossible to estimate the long term effect of HIV/AIDS on the population accurately and hence future water demand. There are two scenarios and these are dependent on local culture and the acceptance of HIV/AIDS positive status by the community. The scenarios are that:
1. Infected people will migrate to larger urban centres for better medical care or; 2. That infected people will return to the rural areas
Based the higher death rates in rural areas (2011 Census) it seems that the infected people may return to rural areas. This may be attributed to the high cost of living in most urban areas.
2.3.4 Population Growth Rates
There are several factors which influence population growth rates, of which the prevalence of HIV/AIDS, increasing access to anti-retroviral medication, declining fertility rates and rural-urban migration are probably the most pertinent to an estimation of the urban population growth rates. Based on the 2001 census results, the Central Bureau of Statistics in the National Planning Commission generated population projections per region for 30 years until 2031 (NPC, 2006).
The NPC population projections are based on the United Nations’ software package, MORTPAK, which uses a variety of input criteria, 12 in total, such as mortality rates, fertility rates, fertility patterns, life expectancy, migration rates and patterns. The input criteria “mortality rate” for example is influenced by the access to health facilities. Should a number of clinics be built in the short term, the access to health facilities would change drastically and with it the mortality rate and the population growth rate.
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The NPC multiplied the figures generated by the MORTPAK package with adjustment factors in order to derive final projection figures for each region, so that the aggregate of the regions populations would tally with the national population estimate.
The low variant population growth rates generated by the NPC, were taken as a basis for this Report because the results of the 2011 Census (NPC, 2012) correspond closely with the low growth scenario until 2031 (NPC, 2006). According to the 2011 Census, the crude birth rate for 2010/11 corresponds with the low variant population projection, whilst the crude death rate corresponds with the high variant population projection made in 2006. This may be a result of urbanisation (smaller families), education and economic growth, which lead to declining family birth rates while mortality rates are much lower in urban areas.
Rural-urban migration is a well-known, though poorly documented phenomenon in Namibia, and it is known that the growth rate of urban centres exceeds that of the natural population as a result. Therefore, with the preparation of the water demand projections, different population growth rates for the urban and rural areas need to be assumed. To make adjustment for rural- urban migration, it was accepted that the rural population will remain fairly constant. Based on the 2011 Census results, the rural population declined by 0.1% between 2001 and 2011.
The Khomas Region and Erongo Region have experienced high rates of in-migration, as more than 40% of residents in these regions were born elsewhere. There have also been high rates of migration into the Karas Region. On the other hand, the Ohangwena and Omusati Regions have had high percentages of out-migration, with more than 20% of the people born in these regions now living elsewhere (NPC, 2012). Provision is made for accommodation in urban areas which normally accommodate migration from other regions. The regional growth rates are summarised in Table 2.3, which are based on the 20011 Census figures.
For the purpose of this Report, it was accepted that the national population growth rate will decline to approximately 1% after 2030 based on the low population growth scenario (NPC, 2006). Similarly, the regional growth rates will also decline with increased urbanisation. In cases such as Windhoek where more accurate growth figures were available, the growth rate was adjusted. In towns in the Cuvelai such as Oshakati, Ondangwa, Ongwediva and Oshikango, higher population growth rates were accepted as suggested in the NamWater Bulk Water Master Plan (LCE, 2009). Table 2.4 gives a summary of urban areas with more than 2,000 inhabitants and the annual growth rates between the 2001 and 2011 based on the Census data.
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Table 2.3: Regional Growth Rates According to 2011 Census Data
NPC 2001 NPC 2011 Urban Percentage Annual Regional Region Census Census Population Urban Growth Rate (Capita) (Capita) (Capita) Zambezi1 79,826 90,596 28,362 31.3% 1.3% Erongo 107,653 150,809 131,770 87.4% 3.4% Hardap 68,246 79,507 47,814 60.1% 1.5% Karas 69,321 77,421 41,823 54.0% 1.1% 2 Kavango 202690 233,352 64,049 28.7% 1.0% Khomas 250,260 342,141 325,858 95.2% 3.1%
Kunene 67,735 86,856 22,898 26.4% 2.3%
Ohangwena 228,383 245,446 24,903 10.1% 0.7% Omaheke 68,041 71,233 21,203 29.8% 0.5% Omusati 228,841 243,166 13,848 5.7% 0.6% Oshana 161,917 176,674 79,801 45.2% 0.9% Oshikoto 161,006 161,973 23,634 13.0% 1.2% Ojozondjupa 135,385 143,903 77,471 53.8% 0.6% Total 1,830,330 2,113,077 903,434 42.8% 1.4%
Notes: 1. Previously the Caprivi Region. 2. The Kavango Region before it was divided into the Kavango East and Kavango West Regions.
Table 2.4: Urban Population Growth Rates in the Study Area
Type of Local Population Population Annual Growth Region Name Authority 2001 2011 (%)
Erongo Municipality Karibib 3,726 5,132 3.25 Erongo Municipality Omaruru 4,761 6,300 2.84 Hardap Municipality Mariental 9,836 12,478 2.40 Hardap Town Rehoboth 21,308 28,843 3.10 Kavango Town Rundu 36,964 63,431 5.55 Khomas Municipality Windhoek 233,529 325,858 3.39 Ohangwena Town Eenhana 2,814 5,528 6.99 Ohangwena Settlement Ongha 1,905 ------Ohangwena Settlement Oshango 2,563 ------Ohangwena Settlement Oshikango 3,058 ------Ohangwena Town Helao Nafidi --- 19,375 --- Omusati Town Outapi 2,640 6,437 9.30 Oshana Town Ondangwa 10,900 22,822 7.70 Oshana Town Ongwediva 10,742 20,260 6.56 Oshana Town Oshakati 28,255 36,541 2.60 Oshikoto Settlement Omuthiya 1,392 3,794 10.54 Oshikoto Settlement Onethindi 2,735 ------Oshikoto Settlement Oniipa 1,738 ------Otjozondjupa Municipality Okahandja 14,039 22,639 4.90 Otjozondjupa Town Okakarara 3,296 4,709 3.63 Otjozondjupa Municipality Otjiwarongo 19,614 28,249 3.72
Note: This table only shows the urban areas with more than 2,000 persons.
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For the purpose of preparing the future projections, it is accepted that the population in a specific region will be the same percentage of the total population for the low growth scenario as determined for each region for the medium growth scenario (NPC, 2006).
2.4 WATER RESOURCES
Up until the turn of the twentieth century, water supply and water demand in Namibia were in balance; people settled where water was found throughout the year, on or near the surface, and moved their livestock between places where water was temporarily available. During the twentieth century, people learned to transport water, dam ephemeral rivers and to tap groundwater to support domestic, agricultural and industrial activities. As the population grew, these various sources were increasingly exploited to promote development throughout the country. Often the sites where people originally chose to settle were places where water was naturally available, but as populations of people and livestock grew, urbanisation and industrial activities increased, these original sources became insufficient (after IWRMPJVN, 2010b).
Only late in the twentieth century did it become recognised that water is the primary limiting factor to development in Namibia. As a result of the increasing water demand, a number of innovative approaches to the management of water supply were introduced and extensive infrastructure established to tap additional sources and to transfer water from where it is available to where it is needed, all with the aim of meeting the increasing demands (after IWRMPJVN, 2010b).
The primary water sources in Namibia are perennial rivers, surface and groundwater (alluvial) storage on ephemeral rivers and groundwater aquifers in various parent rocks.
Waste water is recycled in Arandis, Otjiwarongo, Swakopmund, Tsumeb, Walvis Bay and Windhoek (Mendelsohn et al., 2009) and used for the irrigation of sports fields and gardens, and direct reclamation for potable reuse is carried out in Windhoek.
Namibia’s most recent sea water desalination plant, located 30 km north of Swakopmund and owned and developed by Areva under their Trekkopje mining project, was inaugurated on 16 April 2010.
2.4.1 Surface Water
Namibia’s surface water can be broadly divided into two types; those derived from perennial systems and those derived from ephemeral (seasonal or non-permanent) systems. The latter group includes all the wetland areas and man-made storage dams on or associated with the sporadic flows of ephemeral rivers, as well as pans, pools and other wetlands derived from local runoff (after IWRMPJVN, 2010b).
With the exception of short lengths of the Okavango and Kwando Rivers in the northeast of country, no major perennial rivers are located within the borders of Namibia, and all the rivers in Namibia’s interior are ephemeral (refer to Figure 2.11).
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2.4.1.1 Ephemeral Rivers The low rates of rainfall and high rates of evaporation and evapotranspiration result in low rates of surface runoff and low rates of groundwater recharge. It has been estimated that 83% of the total rainfall evaporates almost immediately. Of the remaining 17%, 14% supports vegetation growth, 2% is surface runoff and 1% contributes to groundwater recharge. Even during the rainy season, stream flow is not continuous and all streams originating in Namibia only flow for a few days a year on average. Hence, the flow in the rivers in the interior of Namibia is irregular and unreliable and the potential of surface water resources is therefore very limited (after JVC, 1993a).
Figure 2.11: Rivers, Basins, Pans and Lakes (Mendelsohn et al., 2009)
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Table 2.5: Estimated Runoff in Ephemeral Rivers in the Interior of Namibia
Mean 95% Distance from Distance from Catchment Annual Assured Windhoek Oshakati River Dam Area Runoff Yield (CAN) (Cuvelai) (km2) (Mm3/a) (Mm3/a) (km) (km) Swakop S. Von Bach 2,9201 182 6.52 63 500 Swakop Swakoppoort 5,4801 222 4.52 73 510 Omatako Omatako 5,3201 32.52 2.03 155 410 Oanob Oanob 2,7301 18.22 4.34 85 655 Fish Neckertal (future) 5502 67.52 458 1,005 Fish Hardap 199.52 54.52 229 776 Löwen Naute 55.12 12.02 492 1,039 Kuiseb Friedenau 2101 3.52 12 40 555 Omaruru Omdel N/A 14 5 85 640 White Nossop Otjivero Main 1,5411 6.12 1.32 96 560 Black Nossop Daan & Tilda Viljoen N/A 2.02 0.22 15 550 Usib Nauaspoort 7021 42 02 57 620 Avis Avis 1021 22 02 5 850 Gammams Goreangab 1311 102 1.52 10 555 Ugab Sebraskop 14,8005 15.12 42 N/A N/A Notes: Values compiled from various sources 1. CAJVC, 2004a. 2. IWRMPJVN, 2010b. 3. IWRMPJVN, 2010b gives 2.0 Mm3/a (Table 8.5) and 7.5 (Table 9.7). 2.0 Mm3/a given elsewhere: CAJVC, 2004a, and WTC, 1997b. 4. 4.9 Mm3/a given in Table 9.5 of the IWRM Report (IWRMPJVN, 2010b). 4.5 Mm3/a given in a June 1989 DWAF Report, Report No. 3121/2/H3. 4.3 Mm3/a given in a March 1998 planning investigation report on Bulk Water Supply to Rehoboth by Alexander and Becker (the latter two figures courtesy of NamWater). NamWater is currently busy with the revision of the yield value. For the time being the most conservative figure available is quoted. Refer also to Section 11.1.1. 5. JVC, 1993a. 6. N/A = Not Available 7. Distances to Windhoek and Oshakati measured “as the crow flies”. Distances from Neckertal Dam measured from Keetmanshoop.
2.4.1.2 Perennial Rivers None of the perennial rivers available as water sources in Namibia originate within the country and all are located on the country’s borders (refer to Figure 2.11). The Kunene (or Cunene), the Okavango and the Kwando-Linyanti-Chobe Rivers, which are located along the northern borders of Namibia, originate in Angola, whilst the Zambezi River, which is located on the extreme north-eastern border, originates in Zambia and Angola (refer to Figure 2.12). The Orange River, which is located along the southern border, originates in the Lesotho Highlands (after JVC, 1993a). Since these border rivers are international watercourses, the abstraction of water from them is subject to international law and agreement with neighbouring states.
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Table 2.6: Runoff in Perennial Rivers Bordering Namibia
Distance from Distance from Catchment Mean Annual Windhoek Oshakati River Runoff Site Area Runoff (CAN) (Cuvelai) (km2) (Mm3/a) (km) (km)
Okavango Rundu 66,3001 5,5003 585 430
Okavango Mukwe 111,2502 10,0003 670 605
Kwando Kongola 100,6004 1,3003 840 806
Kunene Ruacana 89,6005 6,0003 630 135
Zambezi Katima Mulilo 334,0003 40,0006 940 910 Orange Noordoewer 649,931 11,0006 680 1,230
Notes: Values compiled from various sources 1. Mendelsohn and el Obeid, 2004. Inactive catchment area 15,000 km2. 2. Mendelsohn and el Obeid, 2004. Inactive catchment area 45,000 km2. 3. IWRMPJVN, 2010b. 4. JVC, 1994. 5. Pitman and Midgley, 1974. 6. CAJVC, 2004a. 7. ORASECOM, 2007a. 8. Distances to Windhoek and Oshakati measured “as the crow flies”.
Figure 2.12: Perennial Rivers and the Cuvelai System (Mendelsohn et al., 2009)
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The upper catchments of the Okavango and Zambezi Rivers, which drain parts of Angola and Zambia respectively, have been altered the least by human activity. Few dams have been constructed on these rivers, there has been little artificial channelling of the rivers and relatively few agricultural chemicals are used in their catchment areas. By contrast, many dams, both large and small, have been constructed on the Orange River and its tributaries, which also drains large areas of intensively farmed land on which substantial amounts of pesticides and fertilisers are used (after Mendelsohn et al., 2009). The impact of the dams and weirs constructed on the Orange River and its tributaries, is that the flow is heavily regulated, resulting in a much reduced mean annual runoff and maximum flows by the time the river reaches the Namibian border, but increased base flow (IWRMPJVN, 2010a), although floods do still occur in the river.
The Kunene River basin is also largely undeveloped, although dams have been constructed on the river at Matala, Gove and Calueque in Angola, and a weir and hydro-electric scheme have been constructed near the falls at Ruacana. Future hydro-electric schemes (the “Baynes Project”) are being investigated on the portion of the river downstream of the Ruacana Falls.
The Cuvelai basin is unique in the world. The core drainage area consists of hundreds of interconnected channels, called iishana (oshana in the singular), which merge and diverge many times. These make up the seasonal Cuvelai System which originates in the highlands of Angola to the north, where annual rainfall often exceeds 750 mm. The network of iishana initially spreads out and later converges once it crosses the Namibian border, eventually leading to the Omadhiya Lakes and then to the Etosha Pan in the south. Most iishana are dry for much of the year. When water flows in the Cuvelai, this varies, depending on the amounts of rain and where this falls, from small streams to broad fronts of floodwater. A good flow, or “efundja”, occurs in about four out of ten years on average, when water surges down to the Omadhiya Lakes, to the Ekuma River and into the Etosha Pan (after Mendelsohn et al., 2009 and Mendelsohn et al., 2013).
2.4.2 Groundwater Groundwater has played an important role in the development of Namibia. In early times, preferential areas of settlement were near springs or fountains from which groundwater naturally seeped into ponds or even formed the source of small perennial watercourses. Hauchabfontein, Sesfontein and Kowarib are well-known examples and even Windhoek owes its origin to the availability of safe groundwater from flowing springs (after DWA, 2001).
The weather systems, rainfall, surface runoff and open water bodies are the visible components of the water cycle. However, the surface water that infiltrates into the ground fills up the voids and pore spaces of the rock formations making up the crust of the earth, to form groundwater. Whilst this accumulation of water in the aquifers below the surface is not visible, it is an integral part of the hydrological cycle and a vital source of water, particularly to remote and isolated communities (after DWA, 2001).
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Like surface water sources, groundwater can also be regenerated and replenished by rainwater filtering into the ground. The magnitude and sustainable yield of the groundwater sources are therefore determined by the size and extent of the aquifers, the conditions that facilitate the rate of recharge to the aquifers and the potential of the hydro-climate to produce rainfall and runoff. However, there are also fossil groundwaters that have accumulated tens of thousands of years ago in water-bearing aquifers when the climate in the southern African region was much wetter and a lake covered areas in northern Namibia and southern Angola where the Cuvelai Basin is located today (DWA, 2001).
The main groundwater basins or hydrogeological regions of Namibia are shown in Figure 2.13, with the locations of the various types of aquifers and their respective groundwater potential shown in Figure 2.14 and Figure 2.15.
The first drilling machine arrived in Namibia in 1903 and by 1906, there were two drilling units, one for the north and one for the south. In the period since, more than 100,000 boreholes have been drilled and although a large number have either come up dry or dried up over time, it is estimated that there are over 50,000 production boreholes in use in the country. These supply water for mining, industry, domestic use and agriculture over nearly 80% of the country. It is estimated that 45% of the water supplied to towns, villages and farms and 45% of the water used in agriculture comes from groundwater sources (after DWA, 2001). The estimated extent of groundwater sources which currently supply water to the CAN is shown in Table 2.7. The long-term sustainable yield of groundwater in Namibia is estimated to be 300 Mm3/a (DWA, 2001).
Table 2.7: Groundwater Resources Which Supply the Central Area of Namibia
Estimated Distance from Distance from Stored Sustainable Windhoek Oshakati Area / Aquifer Reserve Yield (CAN) (Cuvelai) (Mm3) (Mm3/a) (km) (km) Grootfontein Karst Area I1 20.00 3.82 350 330 Grootfontein Karst Area II1 18.40 3.81 350 330 Goblenz1 3.76 2.71 310 360 Seeis1 1.05 0.09 54 553 Windhoek2 41.00 0.50 0 548 Total: Sources used to Supply the 84.21 10.93 ------Central Area of Namibia
Notes: Values compiled from various sources 1. Refer to Table 4.45 of Part I: CAN Report. 2. Values for the current extent of the Windhoek Managed Aquifer Recharge Scheme. Yield value reflects the capacity of the currently installed infrastructure. Natural recharge from rainfall is 1.73 Mm3/a. 3. Distances to Windhoek and Oshakati measured “as the crow flies”.
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Figure 2.13: Groundwater Basins of Namibia
Figure 2.14: Types of Aquifers and their Productivity (DWA, 2001)
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Figure 2.15: Types of Aquifers and their Productivity (Mendelsohn et al., 2009)
2.4.3 Unconventional Water Resources
Surface water (rivers and dams) and groundwater sources are considered conventional water resources. Unconventional water resources are sources other than these, including (IWRMPJVN, 2010b):
1. The desalination of sea water, 2. The reuse of water to water parks, golf courses and sports grounds, 3. The recycling of water used in industrial and mining processes, 4. The reclamation of water from wastewater effluent, 5. Water banking in aquifers 6. The artificial recharge enhancement of aquifers, 7. The mixing of potable water with brackish water to improve quality, 8. Water demand management through the conservation of water by reducing unit consumption and wastage.
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As communities approach the limit of their conventional (surface and groundwater) sources, unconventional water sources, particularly wastewater reuse and reclamation, become attractive options for conserving and extending available water supplies (after Asano and Bahri, 2011). Whilst the biggest benefit of using unconventional sources is that these do not impinge on the availability of conventional resources (van der Merwe et al., 2013), other benefits include (Asano and Bahri, 2011):
1. Substituting reclaimed wastewater for applications that do not require high-quality drinking water, 2. Augmenting water sources and providing an alternative source of supply, 3. Protecting aquatic ecosystems by decreasing the diversion of freshwater, reducing the quantity of nutrients and other toxic contaminants entering waterways, 4. Reducing the need for control structures such as dams and reservoirs, 5. Complying with environmental regulations by better managing water consumption and wastewater discharges.
2.4.3.1 Desalination Oceans contain about 97% of all the water in the world, but this water has until recently, not generally been viewed as a source of water for human consumption because it is too salty. Desalination is the removal of salt (mostly sodium chloride) and other minerals from the sea water to make it suitable for human consumption and other uses in industry, manufacturing or mining. In 1897, Lüderitz became the first settlement in Namibia to desalinate sea water to obtain potable water, by using a distillation process. Other processes were later used for desalination, until 1967 when fresh water sources were discovered in the Koichab Pan, some 60 km to the northeast of Lüderitz and a pipeline was completed to supply this water to the town (after IWRMPJVN, 2010b).
More recently, a sea water desalination plant with a capacity of 20 Mm3/a, located at Wlotzkasbaken, some 30 km north of Swakopmund, and owned and developed by Areva under their Trekkopje mining project, was inaugurated on 16 April 2010. However, due to declining uranium prices, Areva placed its Trekkopje Uranium Mine on hold during 2012, hence creating space capacity in their desalination plant. NamWater on 15 August 2013 signed an agreement with Areva Namibia to purchase 10 Mm3/a of water from this plant for distribution to three other uranium mines in the Erongo Region. This plant is currently operated by Aveng Water.
A second desalination plant near Mile 6 north of Swakopmund was intended to increase the water supply capacity for the coastal area of Namibia (Swakopmund, Walvis Bay, Henties Bay and the mines in the interior). Tenders for this second desalination plant under a Build, Own, Operate and Transfer (BOOT) basis closed on 29 June 2012, and have since been cancelled (March 2014).
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2.4.3.2 Reuse of Water The indirect reuse of water is the discharge of treated wastewater to the environment in a surface stream for reuse downstream, for ecosystem maintenance and / or for recreation purposes. The treated wastewater may also be discharged in infiltration basins for the artificial recharge of an aquifer and reuse at a later stage. The spatial distribution of urban areas in Namibia, the absence of major perennial rivers inside the country and the high evaporation rates make the indirect reuse of water impossible except for a few urban centres near the perennial rivers along the borders of the country (IWRMPJVN, 2010b).
The direct reuse of water is the treatment of wastewater and the distribution thereof for consumption. Reuse could be via a dual pipe system for irrigation purposes (sports grounds, golf courses, parks and gardens), or could be the augmentation of potable supply or direct groundwater recharge. In Namibia, dual reticulation systems are installed in Windhoek, Walvis Bay, Swakopmund, Otjiwarongo and Tsumeb, and the water is used mainly for parks, sports fields and cemeteries (IWRMPJVN, 2010b).
The recycling of industrial wastewater is the reuse of water in the same industrial or mining process without any further treatment, for example by recycling water from slimes or tailings dams.
The reclamation of domestic sewage water is the treatment of this effluent to potable water quality standards for direct reuse as potable water. The reclaimed water can be blended with the raw water supply to a city, the water in an aquifer, or the potable water supply to a city. Water reclamation for potable reuse from domestic sewage effluent was pioneered in Windhoek in 1968. This system was upgraded several times over the intervening period and the existing plant can be regarded as the 6th generation (IWRMPJVN, 2010b).
The risks of wastewater reuse, however, are significant, since wastewater carries dangerous contaminants, and if improperly treated, reclaimed water could spread disease and health problems. Protecting public health when reusing wastewater requires high standards of regulation and monitoring to guarantee quality. However, due to the emerging nature of this practice, standards and regulations for reuse are not well established. Cutting-edge wastewater reuse technology is also costly and energy-intensive (Smith, 2011).
2.4.3.3 Aquifer Recharge and Water Banking The artificial enhancement or the recharge of an aquifer is a process where surface water runoff is impounded in a dam to allow the sediments and silt in the water to settle in the dam without the addition of chemicals. The clear water is decanted off and recharged into an aquifer by discharging the water into an infiltration pond over the aquifer, which enables the water to infiltrate into the ground and recharge the aquifer. The best example of such a scheme is the project at the Omdel Dam, some 40 km east of Henties Bay on the Omaruru River. Surface runoff in the river is impounded in the dam, and used to recharge the Omaruru Delta through a system of infiltration basins below the dam, once the sediments and colloidal material in the water have settled out in the dam.
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With the exception of the Omdel scheme and possibly the Rehoboth Aquifer in the Oanob River near Rehoboth, the absence of primary (sand) aquifers makes this option very difficult to implement in Namibia (IWRMPJVN, 2010b).
Water banking in an aquifer is a process where raw water in a dam is abstracted and treated in a conventional water purification plant before the water is mechanically injected into an aquifer.
The major difference between water banking and artificial recharge is that the latter is based on natural processes such as the settling of silt and the infiltration of water into the ground. Water banking is carried out in the Windhoek Aquifer where surface water from the Von Bach Dam is treated, pumped to Windhoek and injected into boreholes to recharge the aquifer which is located to the south of the Capital. This water is stored for later use during periods of shortfall in the supply of surface water. This is beneficial since the losses in the Windhoek Aquifer, estimated at approximately 3% per annum (van der Merwe et al., 2013) are significantly less than the evaporation of surface water from the dams, which have an efficiency of less than 35% due to the high evaporation rates in the country (after IWRMPJVN, 2010b).
2.4.4 Inter-Basin Transfers Inter-basin transfers or trans-basin diversions describe man-made conveyance schemes which move water from one river basin, where it is available, to another basin where it is less available, or could be better utilised for human and industrial development. The purpose of such schemes could be to alleviate water shortages in the receiving basin or to generate electricity, or both. Examples in Namibia include the ENWC scheme which augments supply to the CAN, the Calueque Dam – Cuvelai system which supplies the central Cuvelai area, as well as the Central Namib Water Supply System.
Care should be taken with the implementation of inter-basin transfers, to avoid adverse environmental impacts in both the receiving and donor basins.
2.4.4.1 Eastern National Water Carrier Canal Whilst this scheme is often held to refer to the Canal itself, which was constructed over 260 km between Grootfontein and Omatako Dam between 1981 and 1987, the greater scheme consists of several main components:
1. Three surface dams: The Von Bach, Swakoppoort and Omatako Dams, 2. The 260 km Eastern National Water Carrier Canal linking the groundwater sources in the Grootfontein and Karst areas to these dams, 3. Pipeline and pump station infrastructure linking the Omatako and Swakoppoort Dams to the Von Bach Dam, and this latter dam to Windhoek, 4. A pipeline between the Okavango River and Grootfontein, which was envisaged in the 1970s already, but which has not yet been constructed.
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The purpose of this scheme, shown in Figure 1.2, is to augment the local supplies of the CAN, particularly the main area of demand, being the Windhoek – Okahandja complex. At present, water from up to 450 km away, near Grootfontein, is supplied to Windhoek via an integrated system of water supply infrastructure linked to different water sources including groundwater, ephemeral surface water, reclaimed domestic sewage water and water banked underground (after IWRMPJVN, 2010b).
This scheme became a necessity due to the growth of Windhoek, which growth created a demand which outstripped the capacity of local water sources, and the fact that Windhoek is located close to the watershed of three basins. The Omaruru-Swakop Basin originates just to the north of Windhoek, whilst the Kuiseb Basin originates to the west and the Nossob-Auob Basin to the east and south of the Capital.
2.4.4.2 The Calueque Dam – Cuvelai Inter-Basin Water Transfer Scheme Though seldom referred to in such a way, this scheme, shown in Figure 1.3, under which water drawn from the Kunene River at Calueque in Angola, is transferred across the watershed between the Kunene and the Cuvelai river systems and into Namibia, is an inter-basin transfer scheme. This scheme, which was started in the 1960s, now consists of over 100 km of canals, 7,500 km of pipelines and numerous water purification plants, pump stations and reservoirs.
2.5 THE WATER SUPPLY DILEMMA IN NAMIBIA Water can be seen as a limiting factor in all facets of development in Namibia. The lack of water affects human needs, agricultural production, mining, industrial development, manufacturing and power generation. The low and unreliable rainfall severely restricts the possibilities for reliable food production through dryland cropping. Whilst this can be improved by irrigation, this is mostly restricted to areas adjacent to the perennial rivers and consumes vast quantities of water due to high rates of evaporation and evapotranspiration and marginal soils. Stock farming is practiced over most of the country, but the availability of grazing is subject to adequate rainfall and droughts are frequent (IWRMPJVN, 2010a).
The major water demands in Namibia are urban centres and agriculture, in both the communal and commercial farming areas, which demand constitutes approximately 91% of the total water demand (IWRMPJVN, 2010a).
Rainfall in Namibia is low and erratic, and with high evaporation rates, which means that surface runoff is both erratic and sporadic following seasonal rainfall. As a result, little water is available in ephemeral surface sources and for the recharge of groundwater. Namibia’s water resources are moreover unevenly distributed over the country and are generally not located near the major demand centres – the perennial rivers along the country’s borders (refer to Figure 2.10) are a considerable distance from the major demand centres in the central areas of the country. This presents a major challenge to the authorities responsible for water supply to the major demand centres. An overlay of the major water supply schemes in the country and population density which illustrates this is shown in Figure 2.16.
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Figure 2.16: Major Water Supply Schemes in Namibia (Mendelsohn et al., 2009)
Approximate extent of the Cuvelai Area of Namibia
Approximate extent of the Central Area of Namibia
The extent of the water supply schemes in the CAN and Cuvelai, and the interconnected network of canals in pipelines in both instances, relative to the more isolated and discrete supply schemes over much of the remaining parts of the country can be seen clearly in Figure 2.16. In both the CAN and Cuvelai areas, extensive infrastructure is required to transfer water over great distances from where it is available to where it is needed. This presents difficulties in the operation and management of these schemes and particularly in the cost- effective supply of water, given the high cost of such extensive infrastructure and operations.
The surface waters supplying the central area of Namibia are dependent on local rainfall and often erratic runoff. Water consumption however has increased steadily in the central areas, driven by population growth and economic development. The recent Bulk Water Master Plan for the CAN completed for NamWater determined that the water sources supplying the CAN are fast approaching their capacity and that a new water source for the CAN is expected to become a necessity by 2020.
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2.6 WATER DEMAND PROJECTIONS2
2.6.1 General
Water demand projections are required for a variety of purposes, including optimising system operations, planning for the future expansion of supply schemes or for future revenues and expenditure. Several mathematical approaches can be used to estimate the future water demand, including extrapolating historic trends, correlating demand with socio-economic variables, or more detailed simulation modelling. These approaches and models vary in complexity according to the number of variables accounted for and the extent to which water users are disaggregated by sector, location, season, or other factors. Models also vary according to the projection horizon; long-term projecting, as required under this Study, is typically used for infrastructure and capital planning, whilst short-term projections are most useful for planning operations, setting tariffs and estimating revenues and expenditure (after PI, undated).
In Namibia the most common methods adopted for water demand projections appear to be the simple regression and constant growth projection techniques. Although these methods are practical and easy to apply, they are not accurate enough for long-term demand projections and normally lead to overestimation of the future expected water demand. Investment in major capital projects to augment supply should not be based on these over-estimated water demand projections. Alternatively, underestimation could lead to major disruption of economic activity, especially in areas where major variations in annual runoff and recharge of aquifers occurs, as a result of variable rainfall and intensity of rainfall.
In developed countries, the single coefficient method is rarely used for long-term demand projections. Most countries use generic computer models, based on multiple factors influencing water demand and including end use analyses. In most developed countries water demand is more or less stable, or is even declining due to pricing and/or natural conservation.
The reduction in water demand as a result of the real increase of bulk water prices by NamWater is observed in Namibia. Future water demand will also be influenced to a very large extent by future price increases (price elasticity of demand). There is proof in most supply centres that water demand decreased during the past 10 years as a result of water tariff increases. It is estimated that with a 10% real increase of the bulk water supply price, the demand may decrease by 3 to 5%.
2 Adapted and updated from the IWRM Plan for Namibia, Theme Report 2: The Assessment or Resources Potential and Development Need (IWRMPJVN, 2010b.
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The construction, operation and maintenance of water supply infrastructure is expensive, and increasing in real terms, leading to real increases in bulk and retail water tariffs as noted above. This however impacts adversely on poor and severely poor households (refer to Section 2.3.2 above) and their ability to afford basic services. Consequently, the MAWF commissioned a study to investigate the need for and practicalities of water subsidies, the results of which are not yet available.
Due to the incomplete data and almost complete lack of information on the price elasticity of demand, which influences the accuracy of long-term projections (described above), it is recommended that the projections and the planning and implementation of augmentation schemes be reviewed and updated at least once every 4 to 5 years.
Segregated water use projections require water use for each sector, season or region separately, utilising the best available model for each type of water use. This method permits the use of explanatory variables unique to a given type of water use and generally yields a more accurate composite projection. Water use projections could include one or more of the methods discussed, depending on the available data and the most appropriate model for the specific application. Most urban areas such as Windhoek, Okahandja, Karibib and Otjiwarongo provided only short to medium term development information, which compromises the accuracy of long- term demand projections.
Accurate projections depend on the quality of the data and accuracy of future economic / population growth scenarios. In a developing country such as Namibia, where economic / demographic factors change drastically over the short-term, it can be very difficult to predict water demand accurately in the long term. In most of the smaller towns in the Namibia little information was available as an input variable for water demand projections. All future water demand projections are based on assumptions that may vary within the projection period up to 2050.
The types of water demand projections and their applications are shown in Table 2.8.
Table 2.8: Types of Water Demand Projections and Major Applications (PI, undated)
Projection Type Projection Horizon Applications
Hours, days, weeks Optimising, managing systems Very short-term (up to two weeks) operations, pumping
Setting water tariffs, revenue Short-term Years estimation, programme tracking and evaluation Sizing, staging treatment and Medium-term Years to a decade distribution system improvements Sizing system capacity, raw water Long-term Decades supply
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Water demand projections for this Study are of the long-term type, given that the planning horizon extends up to 2050 (refer to Section 1.4.3). It can generally be expected that that the accuracy of demand projections will decrease as the projection horizon increases.
It should be noted that for the purpose of this report all water demand projections are based on NamWater Financial years.
2.6.2 Factors Which Influence Water Demand
The many factors which influence water demand include population growth rates (refer to Section 2.3), Government legislation and policy (refer to Section 2.7.1) and water demand norms (refer to Section 2.6.3).
2.6.2.1 Climate Change The most general definition of climate change is a change in the statistical properties of the climate system when considered over long periods of time, regardless of cause. This term is however mostly used in connection with anthropogenic (caused by humans) global warming. The causes of climate change are many, varied and complex, and similarly the expected implications thereof. It is however expected that climate change will affect temperatures, rainfall, evaporation and runoff patterns, thereby impacting on water availability, usage and demand patterns. It is difficult to incorporate these possible effects into water demand projections, beyond noting that greater variability in weather patterns is expected and that dry periods may become more prolonged and more severe. Consequently, greater variation in water usage and demand, particularly in agriculture, can be expected.
2.6.3 Water Demand Norms Used
The water demand norms used under this Study, as summarised in Table 2.11, were determined from various guidelines, as well as data obtained from places such as Windhoek.
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Table 2.9: Domestic and Other Non-Domestic Water Consumption Norms
Unit of Rate of Category Level of Service Consumption Consumption Communal standpipes (rural)1 ℓ/c/d 25 Walking distance 250 m to 2.5 km Communal standpipes (urban) ℓ/c/d 25 Walking distance 250 m Low income (rural)1 ℓ/c/d 40 Yard standpipe Middle income (rural)1 ℓ/c/d 60 Yard standpipe High income (rural) ℓ/c/d 80 Yard standpipe Low income (urban) ℓ/c/d 55 Middle income (urban) ℓ/c/d 80 High income (urban) ℓ/c/d 130 Low income household (urban) ℓ/house/d 500 Full services Middle income (urban) ℓ/house/d 1,000 Full services High income (urban) ℓ/house/d 2,000 Full services Day scholars2 ℓ/c/d 15 Full services School hostels ℓ/c/d 100 Full services Clinics: Patients and staff3 ℓ/patient/d 30 Outpatient services only Hospital staff and patients ℓ/bed/d 500 Full services Institutional and commercial ℓ/m2/d 5 Full services Notes: 1. The MAWF planning criteria for rural water supply schemes specify 25 ℓ/c/d for communal water points (standpipes). On newer schemes, being those implemented since about 2012, there is an increasing trend towards the provision of individual / private off-takes, usually one per household. Customers typically provide their own pipelines from the water meter manifold to their household. With reduced walking distances, unit demand rates will increase from the 25 ℓ/c/d used previously. 2. Water consumption of scholars and clinic patients in rural areas is additional to that of the demand based on the population figures. 3. Typically in rural areas; ℓ/outpatient/day.
The water demand norms used for agriculture are shown in Table 2.10. With regard to the livestock demand rates, these are for extensive farming conditions and are not applicable to intensive farming activities, which require large volumes of wash water to clean the living quarters of animals.
Table 2.10: Norms for Agricultural Use
Unit of Rate of Category Consumption Consumption
Cattle, horses and donkeys (LSUs)1 ℓ/LSU/d 45
Sheep and goats (SSUs)2 ℓ/SSU/d 12
Irrigation at Etunda and Ogongo m3/ha/a 15,000 Notes: 1. LSU: Large stock unit (or equivalent). 2. SSU: Small stock unit.
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2.7 LEGISLATIVE AND POLICY ENVIRONMENT
2.7.1 National Legislation and Policies
2.7.1.1 Vision 2030 2.7.1.1.1 Goals and Guidelines of Vision 2030 In 2004 the Namibian Government launched Vision 2030, which is an overarching framework for the development of the country. The main goals identified by this vision are that Namibia will be an industrialised, globally competitive, food-secured, country, with a knowledge-based, highly competitive, industrialised, eco-friendly economy with sustainable economic growth and a high quality of life (OOTP, 2004). By 2030, adequate housing with water and sanitation facilities should be available for all. Vision 2030 defines the development goals of Namibia by 2030 as follows: “A prosperous and industrialised Namibia, developed by her human resources, enjoying peace, harmony and political stability”. The main development targets of Vision 2030, are (OOTP, 2004):
1. 80% of GDP from services and processed goods, 2. Processed goods 70% of exports, and 3. Unemployment less than 5%.
Vision 2030 serves as an overall guideline for all national and regional development plans with one of the main aims being to stimulate policy synergies that will link long-term perspectives to short-term development planning initiatives by providing all stakeholders with coordinated and integrated planning directions.
2.7.1.1.2 Aims of Vision 2030 with Regard to the Water Sector This aims of Vision 2030 imply that there will be a substantial increase in the population and, based on a medium growth scenario, will reach 2.998 million in the year 2030, based on the medium population growth scenario (NPC, 2006). To achieve the targets set for Vision 2030, average economic growth rates of 6 to 7% must be achieved until 2030. While high rainfall variability and the accompanying threat of drought are the most critical constraints facing Namibia’s water resources, water demand continues to rise. As a consequence, water scarcity has become a problem for most areas that are placed geographically far from the perennial water sources. The MAEF has estimated that the country’s developed water sources are able to supply a total of 600 Mm3 per annum. Based on projections for future water demand (an estimated average growth of 2.2% per annum) these developed sources are likely to be fully exploited by 2016. Even if stricter Water Demand Management (WDM) practices are enforced, the central areas of Namibia (in particular the high growth points in the Khomas Region) are expected to experience full use of the currently developed sources by 2012. This excludes the full development of the Windhoek Managed Aquifer Recharge Scheme (WMARS).
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Over the next 30 years, water demand in Namibia will increase rapidly in some areas (in particular all expanding urban areas) and only moderately in others. The current problem of distributing the available water to where it will be most needed, will be exacerbated and, due to full exploitation of developed resources, expensive new water sources (for example desalination plants, new dams, long pipelines and water from boundary rivers) will have to be developed. The quantity of water used for high value uses, e.g. tourism (N$ 574/m3), other service sectors and high value crops (e.g. grapes and dates), should increase relative to the quantity used for low values uses, e.g. irrigation of low value crops such as maize (N$ 7.2/m3).
By 2030, equitable access to water should be supported by:
1. Water pricing that reflects the cost of water supply, with 2. Subsidies being fully transparent and mainly restricted to lifeline amounts for low income users.
Greater dissemination and use are to be made of Namibia’s Natural Resource Accounting programme, to inform policies and future development.
The following targets were selected for the Water Sector:
1. Increase water provision from 80% (2006) of the rural population to 85% by 2010; 90% by 2015; 95% by 2020, and to cover 100% of the rural population by 2030, 2. Maintain the current levels of access (95%) to potable water in urban areas until 2006, and achieve 100% coverage by 2010, 3. Ensure that 50% of all water supplied achieves full cost recovery by 2006, increasing to 60% by 2010, 70% by 2015, 80% by 2020, 90% by 2025, and to 100% by 2030, 4. Decentralize 95% of regional rural water supply resources to the regional councils by 2006, and 100% by 2010, 5. Implement gender policy with respect to the water sector by 2006.
Whilst Vision 2030 acknowledges Namibia’s water scarcity in noting that the focus must be “on high value-added services, specialised industries that are modest in their water requirements and information technology” (OOTP, 2004), providing water supply at 100% coverage to both urban and rural areas by 2030, increasing sanitation coverage, and becoming an industrialised and food-secure nation clearly cannot be accomplished without adequate and secure water supplies for all water consumers.
2.7.1.1.3 Urban Water Sector If Vision 2030 is realised the urban population will also increase dramatically from 610,000 (33%) in 2001 to 2,240,000 (75%) in 2030, based on the medium population growth scenario. As an industrialised country, Namibia’s income per capita base would have grown to be equivalent to that of the upper income countries, resulting in a change in status from a lower middle income country to a high income country. Manufacturing and the service sectors would constitute about 80 percent of the country’s gross domestic product.
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The country should export largely processed goods, which would account for not less than 70 percent of total exports. This would give rise to a significant reduction in the export of raw material. Namibia wold have an established network of modern infrastructure such as rail, road, telecommunication and port facilities. Unemployment would be significantly reduced to less than 5 percent of the work force.
The high rate of urbanisation in combination with rising income, access to waterborne sewage and industrial development will increase urban water demand significantly. The construction of new houses (mass housing project of 10,000 houses/annum) in urban areas with provision of full services will increase the water demand significantly in most urban areas included in the Study Area. Because of development patterns and factors influencing the location of industry, a large percentage of the growth may occur in the Central Area of Namibia as well as other growth points along the coast that will require desalinated water.
2.7.1.1.4 Rural Domestic Water Sector With the high rate of urbanisation the rural population will not increase significantly. The recent change in policy by the Directorate of Water Supply and Sanitation Coordination (DWSSC) to provide individual or private connection points through manifolds will increase the rural household demand significantly.
2.7.1.1.5 Irrigation Water Sector Agricultural activities will be modernised and carried out appropriately, thus significantly contributing towards higher incomes and food security at household and national levels, and supporting the sustainable and equitable growth of Namibia’s economy, whilst maintaining and improving land capability. According to the green scheme initiatives, most new irrigation schemes will be concentrated along the perennial rivers which will increase the water requirements significantly.
2.7.1.1.6 Livestock Water Sector Veterinary fences (the “Red Line”) that prevents the spread of contagious livestock diseases, have been essential for the maintenance of livestock exports from herds south of the demarcation, the majority of which are from freehold farms, but have limited the export marketing opportunities of communal farmers in the past. The so-called Red Line will be removed and this will promote effective integration of the domestic agricultural market. Large- scale agricultural activities will focus on the cultivation of high value crops and there will be improved value adding to meat and fish products.
According to the National Agricultural Policy, communal agriculture (which declined over the past 5 years) offers the greatest potential for growth to improve food security, expand income, export of products and rural employment.
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Due to the relatively low livestock carrying capacity, it is doubtful whether these policies will put a major strain on water resources in rural areas. The policy of value addition within the meat industry will require an increase in abattoir capacity, which requires high volumes of water and which may easily contaminate water resources if not carefully managed.
The biggest threat to water resources is bush encroachment, which results from overgrazing. The biomass of bush is much higher than grass and there are major declines in groundwater levels which may be attributed to bush encroachment. No scientific studies on the effect of bush encroachment on the recharge of aquifers are available in Namibia, but similar studies in South Africa have proved that it is worthwhile to remove invasive plants from catchment areas.
2.7.1.1.7 Mining Sector Vision 2030 proposes that Namibia’s mineral resources will be strategically exploited and optimally beneficiated. This will serve to provide equitable opportunities for Namibians to participate in the industry, while ensuring that environmental impacts are minimised. Investments resulting from mining should be used to develop other sustainable industries and human capital for long-term national development. Despite possible rising costs, uncertain prices and variable labour relations, mining continues to maintain its significant contribution towards Namibia’s socio-economic development and is expected to do so into the future, also despite these factors. The small-scale mining sector should grow in relative terms and there would be development of “mining tourism”, where operating mines provide tourism experiences, such as going underground or searching for diamonds, semi-precious stones and mineral specimens.
Mines consume large volumes of water if not properly controlled. It is important to recover the full cost of water supply from mines to ensure that they use water efficiently through recycling and sludge thickening or even belt presses. The pollution threat from slimes dams requires special care especially in the Karst area and other secondary aquifer areas.
2.7.1.1.8 Tourism Sector The tourism sector is identified as the as one of the major growth sectors and the development of high quality, low impact consumptive and non-consumptive tourism should be encouraged. The importance of maintaining the integrity of ecological processes, natural habitats and wildlife populations throughout Namibia will be recognised. The contribution of the direct use of biodiversity in Namibia to the GDP will continue to grow. The benefits of indirect uses associated with natural ecosystems values (e.g. ecosystem functions that provide us with clean air, water and productive soils) that underpin our survival, should be recognised. There should be no conflict between using natural resources and the notion of conservation. Resources should be used sustainably and equitably and appropriate environmental policies and programmes will be implemented.
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The large number of lodges established in Namibia (500+) may increase the water requirement in the sector significantly. Abstraction of water for lodges in ecologically sensitive areas may lead to the over-abstraction of water and inadequate wastewater and refuse disposal may cause groundwater pollution.
2.7.1.2 Namibia’s National Development Plans Since Independence, Namibia has prepared 5-year National Development Plans (NDPs) to guide national priorities and development. The current such plan, Namibia’s 4th National Development Plan, NDP4, covers the 5-year period from 2012/13 to 2016/17. A further three plans, NDP5, NDP6 and NDP7 are envisaged to cover the period until 2030.
2.7.1.2.1 National Development Plan 3 NDP 3, covering the period 2007/08 to 2011/12, identified a key result area for the water sub- sector as ensuring an increase in the availability of water to Namibia from its perennial (border) rivers. One of the key strategies identified for this result area was for Namibia to secure a reasonable and equitable share of water from its international shared rivers (NPC, 2008).
2.7.1.2.2 National Development Plan 4 NDP4 provides direction regarding high-level national priorities, desired outcomes and strategic initiatives, with the aim to guide implementation, whilst leaving the practical details thereof to those institutions with the greatest expertise and capacity to delivery (NPC, NDP4).
With regard to water supply, NDP4 aims to increase the supply of safe drinking water to 100% of the population by 2017, as well as have sufficient water reserves for industrialisation, and ensure the security of water supply. The identified options to address the water constraint include desalination, aquifer recharge, the recycling and reuse of water in industries and the construction of large dams. Large dams are also regarded as important for the irrigation and the Green Scheme development. Water demand is also to be addressed through water-saving technologies in industries and households. Water security is to be ensured for human consumption and industrial development (NPC, NDP4).
In terms of implementation, under “large dams”, construction of the Neckartal Dam on the Fish River has commenced, and under “desalination”, tenders for a second sea water desalination plant at Mile 6 on a BOOT basis closed in 2012 and have since been cancelled (refer to Section 2.4.3.1). However, addressing Namibia’s water scarcity, providing sufficient and secure water for human needs and sufficient water to ensure the envisaged agricultural and industrial development of the country, in line with these policy objectives, will be a major challenge.
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2.7.1.3 Other National Legislation and Policies Other national legislation and policies which provide the framework to the work carried out under this Study include, but are not limited to:
1. The new Water Resources Management Act, Act No. 11 of 2013, 2. The Namibian Water Policy White Paper, 2000, 3. The Water Resources Management Act, 2004, 4. The Draft Water Resources Management Act (Final Version 2011), 5. The Namibia Water Corporation Act, 1997, 6. The National Water Policy, 2000, 7. The Water Supply and Sanitation Policy, 2008, 8. The Local Authority Act, 1992 and the Local Authority Water Supply Regulations, 9. The Environmental Management Act, 2007 and the accompanying regulations, 10. The Decentralization Policy, 1997,
These acts and policy documents are dealt with in detail the Theme 1 Report [Review and Assessment of Existing Situation] of the Integrated Water Resources Management Plan for Namibia (IWRMPJVN, 2010a).
2.7.2 Regional Policies and Agreements
Regional policies and agreements which have a bearing on the work carried out under this Study include:
1. The Revised SADC Protocol, 2. The Permanent Water Commission on the Orange River between Namibia and South Africa, 3. The Permanent Okavango River Basin Water Commission (OKACOM) between Namibia, Angola and Botswana, 4. The Permanent Joint Technical Commission (PJTC) on the Kunene River between Namibia and Angola, 5. The Kunene Transboundary Water Supply Project (KTWSP), which is a Southern African Development Community (SADC) Pilot Project under the Regional Strategic Water Infrastructure Development Programme,
2.7.3 International Law and Principles
International law and other principles, agreements and documents which have a bearing on the work carried out under this Study include:
1. The 1997 United Nations Convention on the Law of the Non-navigational Uses of International Watercourses, 2. The Dublin Principles, 3. The Millennium Development Goals, 4. The Equator Principles.
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INTRODUCTION TO THE CUVELAI AREA
3.1 PROJECT AREA IN THE CUVELAI
3.1.1 Introduction The Cuvelai area is commonly used to refer to an area which stretches across the Omusati, Oshana, Ohangwena and Oshikoto Regions in northern Namibia, from the border between the Kunene and Omusati Regions in the west to the border between the Oshikoto and Kavango Regions in the east. This area is bounded by the Angola – Namibia border to the north and the northern boundary of the Etosha National Park to the south.
Figure 3.1: Location of the Cuvelai Area of Namibia
In hydrological terms, being a trans-boundary wetland system, this (greater) area is termed the Cuvelai-Etosha Basin (CEB), or in Namibia, the Cuvelai Basin (refer to Figure 3.2). Geologically, this area, being part of the greater Kalahari Basin, is known as the Owambo Basin. The Cuvelai, Cuvelai-Etosha and Owambo Basins therefore describe largely the same area (after Mendelsohn et. al., 2009), but importantly, extend to the surface water watershed located to the south of Etosha.
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Figure 3.2: The Cuvelai-Etosha Basin
The Cuvelai Basin, in hydrological terms, is bound in the south and west by the surface water divide running from Otavi to Outjo, Kamanjab, Otjovasandu, Otjondeka, Opuwo and Ruacana. In the east, the boundary is formed by a faint groundwater divide running north from Tsintsabis almost at 18° longitude (which is also the border between the Oshikoto and Kavango Regions), whilst in the north, it is the international border between Angola and Namibia (DWA, 2001).
For the purposes of this Study, the Cuvelai area refers to the area south of the Angola – Namibia international border, to the north of the northern border of the Etosha National Park and the area between the Kunene Region to the west and the Kavango Region to the east.
3.1.2 Climate
Descriptions of the rainfall, temperature, evaporation and water deficit, and elevation, relief and geology of the Cuvelai area are referred to briefly in Section 2.2, as well as below. Further details, including those of the soils, vegetation, natural and agricultural land resources, present land use and future opportunities, land administration and infrastructure are contained in the Combined Regional Rural Water Supply Development Plan for the Omusati, Ohangwena, Oshana and Oshikoto Regions (LCE, 2011) as well as the Profile and Atlas of the Cuvelai- Etosha (Mendelsohn et. al., 2013).
3.1.2.1 Rainfall The Cuvelai area of Namibia has hot semi-arid or steppe climate (BSh according to the Köppen- Geiger Climate Classification – refer to Section 2.2.2), which is characterised by rainfall which varies greatly in amount and timing from the east to the west of the area. Almost all the rain falls during the summer months, when temperatures are highest, roughly between November and April. The eastern areas generally receive higher and more reliable rainfall than the western areas. Average rainfall varies from about 350 – 400 mm per annum in the west to about 550 – 600 mm per annum in the east (Mendelsohn et al., 2013).
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Most of the rain-carrying air blows in from the north-east and north, providing these areas with rain at the beginning of each rainy season, leaving less moisture to fall further south and west of the region. The hills in the vicinity of Tsumeb forces the incoming air upwards where it cools, condensing the water vapour resulting in higher rain falls in that area. Figure 3.3 indicates the average annual rainfall in the Cuvelai area.
Figure 3.3: Average Annual Rainfall across the Cuvelai Area (Mendelsohn et al., 2000)
3.1.2.2 Temperature and Humidity Average daily temperatures rise from about 17º Celsius in June and July to about 25º Celsius in October, November and December. These three months and September also have the highest maximum temperatures for the year of between 30º and 35º Celsius. The summer months that follow are generally cooler due to the effects of cooling rain and greater cloud cover. Average minimum winter temperatures drop to about 7º and 8º Celsius and very few days with temperatures close to zero are encountered. Frost may occur very occasionally further south in the region (Mendelsohn et al., 2000).
Mean monthly values of humidity range from up to 80% in March, which is the most humid month in the Cuvelai, to less than 20% in September, which is the least humid month (Mendelsohn et al., 2013).
3.1.2.3 Evaporation and Water Deficit Temperature, humidity, cloud cover, wind and solar radiation all influence evaporation rates. Approximately 2,000 mm of water evaporates from the surface each year. With an average annual rainfall of between 400 – 500 mm, this means that considerably more water (about four or five times more) evaporates than falls each year. The water deficit, being the difference between relatively low rainfall levels and high evaporation rates, causes the arid conditions of the Cuvelai area, varying from about 1,700 mm/a to about 1,300 mm/a from west to east across the Cuvelai (refer to Figure 2.6).
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Evaporation rates are highest between September / October and December / January because of the heat and the stronger winds that prevail in this period, as well as lower levels of cloud cover. Evaporation levels drop during the peak rainfall period as a result of higher levels of cloud cover which reflect hear. Overall, high evaporation rates mean that water dries up soon after the rainy season. As the water in the iishana evaporates, the salinity increases, and the nutritional values decrease.
3.1.2.4 Winds Wind direction is highly variable, although for much of the year winds blowing across the Cuvelai come largely from the north-east and east. This is more the case during the winter months of May to September, than during the summer months of October to April when the wind direction is more variable. Wind speeds are generally lowest at night and early mornings, reaching a maximum around 14h00 in the afternoons. Average wind speeds in the area are generally moderate and fluctuate between 4 to 13 km/hour at 14h00 in the afternoon (Mendelsohn et al., 2013).
3.1.3 Biophysical Environment
3.1.3.1 Geology1 The Cuvelai area is situated in the intra-continental Owambo Basin, which was formed during the post-cretaceous tectonic development of southern Africa. Refer to Figure 3.4 below. A sedimentary rock cover of up to 8,000 m thick was deposited in the late Precambrian Age on top of the mid- Proterozoic crystalline basement (Congo Craton). During the Lower Permian to Jurassic, the sediments of the Nosib, Otavi and Mulden Groups of the Damara Sequence were covered by sedimentary deposits up to 360 m thick and volcanics of the Karoo Sequence. A succession of semi-consolidated to unconsolidated sediments of the Kalahari Sequence of up to 600 m thick overlay the intrusive and extrusive rocks of Karoo Age. In Table 3.1 below, the wide suite of rocks in terms of lithology and age are summarised.
The sedimentation of the Damara Sequence started on a rifting margin some 900 Ma with terrestrial-fluvial sandstone of the Nosib Group, followed by the carbonates (mainly dolomites, with some limestones and shales) of the Otavi Group at 730 to 700 Ma). The Mulden Group was deposited as an erosion product of the upliftment taking place between 650 and 600 Ma and consists in sandstone, siltstone, shales and carbonate. In the Cuvelai area, the Damara Sequence rocks are restricted to the western mountain ridge.
1 Extract from the “Combined Regional Rural Water Supply Development Plan for the Oshikoto, Ohangwena Oshana and Omusati Regions”, LCE, 2011.
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Figure 3.4: Geology of the Cuvelai Basin
The Karoo Sequence, consisting of fluvio-glacial sediments (tillite, sandstone, carbonates and shale), are not out-cropping but are found in the boreholes logs. To the north of Tsumeb, intrusive dykes were found passing through the Kalkrand Formation both from the Karoo sequence. A number of boreholes in the Cuvelai Etosha Basin (CEB) penetrate the Karoo rocks at depth.
The Kalahari Sequence ranges from late Cretaceous to Quarternary and is entirely continental, ranging from Aeolian to fluvial deposits. The Aeolian material consists of fine-grained well- sorted sands, while the material deposited in a fluvial environment ranges from gravel to clay and often represents braided stream conditions. The fluvial sedimentation dominates, with some reworking of Aeolian sand. The Kalahari Sequence reaches a maximum thickness of more than 600 m in the north-east of the CEB (Okongo area). Braided river conditions within the intra- continental basin environment result in a vertically and horizontally very variable lithology. This lithology consists in red beds (conglomerate, shale and sandstone) at the base from the Ombalantu Formation, underlying the Beiseb Fromation (Eocene), consisting in brown and grey sandstone and/or mudstone and reaches a maximum thickness of 30 m.
The reddish brown sand/sandstone Olukonda Formation overlies locally (north-west of Oshivelo) the Beiseb Formation. The sedimentation process was not continuous, as there were periods of erosion in-between, resulting in palaeosols and fossil peneplains, which were reworked. One of such palaeosols is believed to be an aquiferous horizon. Over the Olukonda Formation, the semi-consolidated to consolidated sand of the Andoni Formation are found.
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Calcrete has formed in all sediments of the Kalahari Sequence and in particular at the top of the Andoni Formation, locally being karstified. Recent Aeolian sand covers much of the Cuvelai area to various depths.
Table 3.1: Geological Formations in North Central Namibia
In terms of geological structures, the deep sand cover makes the depiction of the faults and strikes throughout the CEB difficult. The studies undertaken with the help of aerial photographs and satellite images recognized the following described features: a major fault, namely the ‘Etosha Fault’ at the south to south-eastern margin of the Etosha Pan which seems to be parallel to the faults along the Okavango Delta in Botswana and the Linyanti-Chobe system of the Eastern Zambezi (Caprivi) Region and the origin to the occurrence of the Etosha springs.
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The existence of basalt dykes and dyke swarms of Karoo Age that extend further north from the Otavi Mountain Land is mentioned by others.
3.1.3.2 Topography of the Cuvelai Basin The topography of the Owambo or Cuvelai Basin is characterised by an extremely flat plain which forms part of the Etosha Depression and gradually descends like a shallow trough from north to south towards the Etosha Pan, which is the lowest part of the Basin. The gradient of the plain is approximately 1:2,500 between the Angolan Border and Ondangwa and between 1:5,000 and 1:10,000 further south to the Etosha Pan. The elevation of the plain is between 1,090 and 1,150 m amsl (DWA, 1991). The highest points rise over 1,500 m amsl in the Tsumeb hills, whilst elevations on the western border of the area average about 1,200 m amsl The only exception to the flat topography is found in the western extremity of the area, where the land rises gently to the foothills of the Kaokoland mountain ranges, in contrast to the rugged hills and the escarpment along the deep valley which has been carved into the northwestern fringe of the plains by the Kunene River. The elevation below the Ruacana Falls, which has a height of about 130 m, is 750 m amsl (DWA, 1991)
3.1.3.3 Drainage The north-central part of Namibia is characterised by extremely flat plains, drained by a network of drainage paths known as the Cuvelai system, which originates in southern Angola and includes a catchment area extending as far north as the central highlands of this neighbouring country, and which conveys flows southwards into Namibia.
The ephemeral channels in the Cuvelai system normally fill up from local rains during the rainy season, but this normally results in little continuous flow. During much of the year, the depressions or pans are dry and serve as grazing areas. During good rainy seasons in the upper catchment in Angola however, the flood waters can reach Namibia, resulting in the so- called efundja flood situation. These flows then move slowly down the catchment and converge at the Omadhiya Lakes and the Etosha Pan.
Although the entire drainage system is customarily termed the “Cuvelai”, the system actually consists of 9 drainage areas which all flow southwards from areas of higher elevation and rainfall in Angola, converge on the Omadhiya Lakes, to eventually drain towards the Etosha Pan (refer to Section 4.3 for further details).
The Omadhiya Lakes (Lake Oponono), the Cuvelai iishana and the Etosha Pan are regarded as wetlands of international importance in terms of their ecology and hydrology, which recognition was formalised by the designation of these areas as Ramsar Site No. 745 in 1995.
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Figure 3.5: Drainage System of the Cuvelai Basin (Mendelsohn et al., 2000)
3.1.3.4 Soils Almost all the soils in the Owambo basin have been deposited there by water and wind. Those laid down by water are fine-grained clays and silts, while vast layers of sand were deposited by wind. Water and wind forces were also responsible for mixing the various deposits within the basin, churning, cutting and shaping the deposits into long features (dunes and Iishana), circles (pans) and layers of different soils. Sands have generally remained where they were deposited or have piled up on higher grounds, while the silts and clays lie in the pans.
Generally, the Cuvelai area is underlain mostly by sediments of silt, clay, limestone and sandstone, which soils generally have a low potential for crop cultivation due to poor water holding capacity, low nutrient content, high salt content and hard layers of clay below the surface (Mendelsohn et al., 2000). Figure 3.6 indicates the different soils types in the Cuvelai area.
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Figure 3.6: Soils in the Cuvelai Basin (Mendelsohn et al., 2000)
3.1.3.5 Vegetation As described by Mendelsohn et al. (2000), 35 different vegetation units have been recognised and described in the Cuvelai area. This has been done mainly on the basis of differences in the structure of woody plant growth, plant species composition, and soil type.
The eastern part of the Cuvelai area (eastern Kalahari woodlands) accommodates large trees and shrubs that have deep roots extending down to moisture in the deeper layers. The community of woodlands and shrubs is very diverse, with species that prefer clayey soils in the scattered pans, old drainage lines and inter-dune valleys.
The Cuvelai hosts the iishana and surrounding lowlands. During the dry season, most of the iishana are covered by grass, while on the higher ground in between, saline Kalahari sands support Mopane scrub and various larger trees. These raised areas also support much of the crop production and grazing areas – various saline grasses dominate the vegetation. The vegetation in the Cuvelai area is generally in poor condition, more so in the north western portion of the area, with the eastern areas generally featuring better vegetation cover.
The western part of the Cuvelai area (western Kalahari woodlands) is much more arid than the eastern portion, where the woody growth consists more of shrubs and open tree savannah. The vegetation changes from a community of open, short shrubs dominated by acacia species and Mopane in the south-west, to heterogonous savannah of taller Mopane in the far north-west.
Figure 3.7 shows the different vegetation type found in the Cuvelai area.
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Figure 3.7: Vegetation in the Cuvelai Basin (Mendelsohn et al., 2000)
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3.1.4 Water Supply
Water which enters the Cuvelai area, either as rainfall or flowing surface water in the Cuvelai system, rapidly evaporates or seeps into the sandy ground (Mendelsohn et al., 2000). Water which accumulates in the iishana is used for livestock watering and domestic use before the iishana dry up, typically during the dry winter months, after which no surface water is available until the next rainy season.
Traditionally, shallow, hand-dug wells or omithima, located throughout the Cuvelai area, have been used to draw water from shallow perched aquifers after the iishana have dried up. However, useful amounts of water are only located in certain places, some of these wells dry up during the winter months, and most of the water drawn from these wells is saline and unfit for human consumption.
Some deeper wells, or oondungu, have been dug to draw water from the deeper saline aquifers in certain parts of the Cuvelai. However, this water is often too saline for human consumption, and in some places, such as at Okashana, it is almost too saline even for livestock consumption.
Historically, the extraction and desalination of groundwater has been deemed unfeasible, and consequently most of the population in the Cuvelai area therefore rely on the extensive pipeline network for a reliable source of water, particularly during the dry winter and the months immediately preceding the rains, during which time the demand on the water supply system is at its peak.
3.1.5 Population
As far back as 1968, the Cuvelai was noted to be the most densely populated area of the country (DWA, 1968) and this remains so today. Based on the results of the 2011 Population and Housing Census, approximately 844,500 people live in the Ohangwena, Omusati, Oshana and Oshikoto Regions, which comprises approximately 40% of Namibia’s total population (NPC, 2012). These four regions however comprise only 10% of the area of Namibia, resulting in population densities well above the national average.
With over 20 people per square kilometre, the Ohangwena and Oshana Regions are by far the most densely populated regions in the country.
The population density of Cuvelai area can be expected to be higher than that of the Ohangwena, Omusati, Oshana and Oshikoto Regions combined (shown in Table 3.2), since a large portion of the Oshikoto Region is located south of Oshivelo and consists of commercial farmland, which area is not generally accepted to fall within the Cuvelai area.
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A distribution of the population densities in the Cuvelai area is shown in Figure 3.8, which was compiled using aerial photographs of the area from 2008 and average household sizes as obtained from the various regional poverty profiles (LCE, 2011). No major changes are expected in this population distribution compared with the results of the 2011 population census.
Table 3.2: 2011 Population of the Ohangwena, Omusati, Oshana and Oshikoto Regions
Population Area Population Region Total % of Area % of Density 2 2 (capita) Total (km ) Total (c/km ) Ohangwena 245,100 12% 10,706 1% 22.9 Omusati 242,900 12% 26,551 3% 9.1 Oshana 174,900 8% 8,647 1% 20.2 Oshikoto 181,600 9% 38,685 5% 4.7 Four North-Central Regions 844,500 40% 84,589 10% 10.0
Namibia Total 2,104,900 100% 825,615 100% 2.5
Data from the 2011 Preliminary Census Results (NPC, 2012)
Figure 3.8: Distribution of Population Densities (2008) (LCE, 2011)
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Urbanisation levels have increased in all four north-central regions from 1991 to 2001 to 2011, as shown in Table 3.3, with the Oshana Region featuring the highest urbanisation levels of these four regions at each time interval. As urbanisation levels have increased, population densities have increased (refer also to Figure 2.10), and Oshakati (588 c/km2), the fifth largest town in Namibia, now features a higher population density than Windhoek (451 c/km2) (NPC, 2012).
The urban population of Ondangwa has increased by 89% and that of Oshakati by 109% over the ten-year period between 2001 and 2011.
Table 3.3: 2011 Urban Population of the Ohangwena, Omusati, Oshana and Oshikoto Regions
Population Growth Rate Urban Area (Capita) (% per annum) 2001 2011 Eenhana 2,814 5,528 7.0 Helao Nafidi --- 19,375 --- Outapi 2,640 6,437 9.3 Oshikuku --- 2,761 --- Okahao --- 1,665 --- Ondangwa 10,900 22,822 7.7 Ongwediva 10,742 20,260 6.6 Oshakati 28,255 36,541 2.6 Omuthiya --- 3,794 --- Ruacana --- 2,985 --- Total 55,351 122,168 8.2 Notes: 1. Data from the 2011 Census Results Main Report (NSA, 2012a), 2. Some centres such as Helao Nafidi were not declared urban centres in 2001.
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3.2 ECONOMIC & OTHER IMPORTANCE OF THE CUVELAI AREA
3.2.1 Population Growth and Private Consumption
Population growth between 2001 and 2011 in the Ohangwena (0.7%), Omusati (0.6%), Oshana (0.9%) and Oshikoto Regions (1.2%) has been below the national average (1.4%) (refer to Table 2.3).High growth rates have been experienced in the urban areas of the Cuvelai however, although in some instances this is due to the classification of urban areas and the configuration of the enumeration areas (refer to Table 3.3).
The four regions of Ohangwena, Omusati, Oshana and Oshikoto1 together accounted for a total household consumption of N$ 7.124 billion in 2009/10, or nearly 25% of the national total, placing this combination behind only the Khomas Region (37%) and ahead of the Erongo Region (11%) in a ranking by region or area (NSA, 2012b). These four regions also accounted for approximately 25% of the national household consumption in 2003/04 (CBS, 2006), indicating the sustained economic value within and of this area.
The per capita consumption in these regions is not amongst the highest in the country, most likely due to the high reliance on subsistence agriculture which would reduce expenditure on households’ food purchases. Nevertheless, the high household consumption in the Ohangwena, Omusati, Oshana and Oshikoto Regions indicates the concentration of wealth in and the economic importance of this area to the country as a whole.
3.2.2 Building and Construction in Oshakati
Following the closure of the Namibian Economic Policy Research Unit (NEPRU), economic reports, such as those published by the Institute for Public Policy Research (IPPR) for example, no longer provide figures per centre or region, such as for the Cuvelai, but by economic sector (for example mining, tourism, fisheries etc.). These are therefore of little use in deducing the economic importance of an area such as the Cuvelai. Given the lack of formal economic data for the Cuvleia therefore, the value of building and construction work in the central urban areas of Oshakati, Ongwediva and Ondangwa was sought as an indicator of the economic importance of the area. These are the largest urban centres in the Cuvelai, with Town Councils, from whom such information should be available.
To date, only the Oshakati Town Council has provided information, shown in Table 3.4, regarding the value of projects implemented by them in their 2013/14 financial year.
1 The National Household Income and Expenditure surveys only provide data per region and not per town or other delineation such as the Cuvelai.
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Table 3.4: Value of Projects Implemented by the Oshakati Town Council in 2013/14
Project Value Project Description (N$ million)
Construction of services at Ekuku 117 (water, sewerage, roads and electricity)
Construction of bulk services at Eheny 23 (water, sewerage, roads and electricity) Construction of municipal services in Extension 16 79 (water, sewerage, roads and electricity) Surfacing of roads 3.3 Construction of open market 40 Total 262.3
Given the lack of economic data for the Cuvelai area, the value of building and construction initiated by the Town Council in Oshakati alone is a strong indicator of the economic importance of this area.
3.3 HISTORY OF WATER SUPPLY IN THE CUVELAI 3.3.1 The Assessment and Planning of Water Supply Infrastructure in the Cuvelai
From the late 1960s, starting with the 1968 Ovamboland Master Water Plan, which was the first comprehensive such assessment, the water supply situation, being the demands, the capacity of the supply sources, and the existing and required infrastructure, has been assessed at regular intervals. A selection of these assessments is provided below.
3.3.1.1 The 1968 Master Water Plan (DWA, 1968) The 1968 Master Water Plan reported that assessments of the flow of the Cuvelai at Oshakati over the past 27 seasons showed that in nearly 40% of the seasons no flow whatsoever was registered and that the flow in the Cuvelai system could only be relied upon 50% of the time. It was therefore recognised that the local water sources, being intermittent and unreliable, would never be sufficient for large-scale expansion to provide a self-supporting economy (after DWA, 1968). The 1968 master water plan therefore recognised that bringing in Kunene River water, by pumping at Calueque (earlier known as Eriksondrift), is the most urgent part of the scheme for supplying the Cuvelai with its water needs and its “extension into the interior of the area forms the very foundation for comprehensive satisfaction of water demand” (DWA, 1968).
Consequently, the 1968 water master plan assessed the expected future water demand of the Cuvelai, including irrigation, examined the existing water supply infrastructure and proposed ambitious plans for the extension of water supply infrastructure, including (after DWA, 1968):
1. The drilling of a large number of new boreholes: a. 332 new boreholes in the area to the west of the central Cuvelai in four phases, b. 454 new boreholes in the area to the east of the central Cuvelai in four phases, 1. The construction of some 300 excavation and pump storage dams in the central Cuvelai,
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2. The construction of some 60 wells and 140 cisterns for small rural schools and clinics, 3. The Construction of the Calueque Pumping Scheme consisting of: a. A pump station on the south bank of the Cunene River, using direct diversion until such time as a dam is built, with 2 m3/s capacity pumps installed, b. A 2,500 m long rising main, c. A 12 km long canal to the border near Mahenene, 4. Construction of a system of canals as follows: a. The Mahenene – Ombalantu Canal over 47 km to connect to the existing Outapi (Ombalantu) – Oshakati Canal, b. The report recommended the use of a canal as the only satisfactory structure given the need for future irrigation in the area, c. The initial portion of the canal from the border to the Oshana Olushandja should be sized for the full agreed-upon abstraction rate of 6 m3/s from the Kunene River and fully lined, d. Provision should be made for a bifurcation which can be used for the future supply to the Etaka Canal, Kaokoland and further to the south, e. Surplus flow is to be stored in the Oshana Olushandja which is to provide balancing storage in the order to 40 Mm3/a by the construction of a relatively low embankment in the north and partial excavation and the installation of sluices on the southern end, f. At Onanime, some 26 km from the border, a branch canal to the south east to serve an irrigation area is to be provided, g. The capacities of the canals are to reduce along the route towards Oshakati, h. The concrete lining of the canals was the most economical and acceptable solution. The sides could be lined initially, with the lining of the invert left for later in order to save costs, i. The iishana be crossed by means of siphons, j. Due to the fact that the Outapi (Ombalantu) – Olushandja Canal was conceived as a flood water collector, its construction was kept as simple as possible. Problems had however been experienced with the maintenance of the canal, due to erosion of the banks, and the washing in of silt from overland flow. Improvements, including fencing, bridging, siphon crossings and side drains were therefore proposed, k. It was found that pumping water in the section from Olushandja to Outapi (Ombalantu) would be more than double the cost of a canal, l. For the Outapi (Ombalantu) – Oshakati section, the existing flood water collecting canal rendered the “suggestion of replacement by pipeline very disadvantageous in respect of comparative values”. The use of canals over pipelines was found to be advantageous given that the timeframe for the commencement of irrigation was not known at the time, m. The construction of parallel branch canals for irrigation, n. Linking the Etaka Canal to the bifurcation on the Mahenene – Olushandja canal in order to provide water along the western portion of the central Cuvelai,
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o. Extension of the Oshakati Canal southwards to Lake Oponono (40 km), and similarly the extension of the Etaka Canal to end in the lake (75 km), 5. Piped water supply as follows: a. From Oshakati towards the Oshikango complex at Engela (45 km long, 12 inch diameter reducing to 10 inch diameter halfway along the route), b. Smaller branch pipelines outwards from Engela, c. An extension of the pipeline system from Ondangwa towards the east, d. The branch pipelines from Engela and Ondangwa were estimated to be some 330 km in extent, e. Pipelines southwards from the Etaka Canal, 6. Water purification works as required, 7. The costs of the scheme as a whole were estimated to be N$ 30 million.
3.3.1.2 The 1974 Master Water Plan In 1974 a second master plan for the Cuvelai was published, which amended some aspects of the 1968 plan. Due to the outbreak of hostilities in Angola, the Calueque Pumping Scheme was not in use in 1978, and instead, water was pumped from “Hippo Pool” in the Kunene River downstream of the Ruacana Falls to Olushandja Dam, for further distribution (Claassen and Page, 1978).
The 1974 Master Water Plan for the Cuvelai identified the following as the most important proposals regarding the upgrading of the regional bulk water supply network (DWA, 1991):
1. An improved water supply link between Outapi (Ombalantu) and Oshakati, 2. The upgrading of the pipeline between Oshakati and Ondangwa, 3. New pipeline networks to the north and southeast of Ondangwa, and from Outapi into the area north of the Etosha National Park, 4. An irrigation project to the east of Eunda.
3.3.1.3 The 1991 Master Water Plan (DWA, 1991) Since good progress had been made with infrastructure development in the Cuvelai since 1974, it was considered appropriate to re-evaluate the existing water supply strategy for the area, for which the following were considered aspects of fundamental importance (DWA, 1991):
1. To secure the necessary access to the Calueque Dam by ratification and honouring of existing agreements, 2. To upgrade critical bulk water supply lines by increasing their capacity, 3. To construct additional pipelines to introduce water for domestic use and stock watering purposes into the rural areas, 4. To embark on small and large scale irrigation projects to support the cultivation of agricultural produce for local use and export, 5. To improve local rural water supply and sanitation facilities, 6. To programme the establishment of water supply projects according to water demand projections.
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This master plan assessed the current (March 1990) water supply situation in the Cuvelai, identified the problems with the existing bulk water network and proposed remedial measures for these, and put forward proposals for extending the water supply network and increasing the utilisation of surface and groundwater sources.
The 1991 Master Water Plan concluded that the magnitude and reliability of the local surface water sources in the Cuvelai was questionable and that local groundwater was insufficient to support urban development. It was consequently recommended that the bulk water supply network be upgraded and extended to ensure the security of water supply for a developing Cuvelai.
Three priorities were identified in order to achieve this; firstly the upgrading of the capacity of the major or most critical components of the bulk water supply network, secondly the construction of minor bulk supply pipelines to important urban centres not already connected to the network and thirdly to link smaller rural communities with distribution pipelines from the bulk water supply network. It was also proposed that at least 2,000 wells be upgraded or developed and that at least 600 boreholes would be required to provide water for domestic and stock consumption (after DWA, 1991).
3.3.1.4 1991 Investigation into the Surface Water Resources of Owambo In 1991 the Hydrology Division of the DWA was instructed to carry out the first in-depth investigation into the surface water sources of the Cuvelai area, and concluded (after DWA, 1995):
1. The frequency and magnitude of flow in the Cuvelai System were not well known, but that it appeared that the flow was highly unreliable, 2. Due to the flat terrain, finding good sites for major dams was virtually impossible, 3. A better potential was tentatively identified in the existing, but neglected smaller excavation dams, which could be used on a smaller scale to augment rural water supply, mainly for stock watering.
3.3.1.5 1995 Re-Evaluation of the Potential for Large Dams in the Cuvelai Delta (DWA, 1995) Following improved monitoring of the flows in the Cuvelai since 1991, and the availability of more data, a re-evaluation of the surface water potential and that for large dams was undertaken. The findings of this assessment can be summarised as follows (after DWA, 1995):
1. Large dams: Although the flow characteristics of three sites tentatively identified for large dams were not unfavourable, such dams were found to be unfavourable because of: a. The very flat terrain and high evaporation losses, b. Due to the high turbidity of the water in the Cuvelai system, extensive water treatment would be required to supply potable water from such dams, which together with the high cost of the dams, would make the water very expensive,
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c. Due to the very flat terrain, large areas would be inundated, which might require the relocation of people, services and infrastructure, as well as resulting in the loss of land for agriculture, d. Changes in the drainage patterns could have negative environmental impacts, 2. Large excavation or pumped storage dams: Although more favourable storage-to-depth ratios could be obtained with artificial pumped storage or excavation dams, such dams would be unfavourable since: a. The cost of this water would be several times that pumped from the Kunene River, b. There is a potential danger of saline groundwater intrusion, c. The concentration of people and animals around the dams could have negative environmental consequences, d. Other water sources would still be required to cater for the years when little or no flow occurred in the iishana, 3. Small excavation dams: That these be considered as the presently most suitable manner to utilise the surface water of the Cuvelai Delta, and that these be used mainly for stock watering.
3.3.1.6 1998 Investigation into a Pipeline Scheme from the Okavango River (TIDI, 1998) 3.3.1.6.1 Agreements Between the Namibian and Chinese Governments The Chinese and Namibian governments signed a Memorandum of Understanding on and Terms of Reference for the Reconnaissance Study of the Okavango River – Ohangwena/Oshikoto Regions Water Supply Project on 08 November 1996. The costs for the Chinese experts to undertake this study were to be covered under the assistance grants provided in the Agreement on Economic and Technical Cooperation signed between the Governments of the Republic of Namibia and the People’s Republic of China on 19 May 1996. According the Memorandum of Agreement and Terms of Reference, Tianjin Investigation, Design and Research Institute (TIDI) under the Ministry of Water Resources of the People’s Republic of China, was entrusted with sending experts to Namibia in March 1997 to undertake field visits, collect the necessary data and complete this project.
3.3.1.6.2 Project Objectives Based on a letter from the Permanent Secretary of the MAWF (the MAWRN at the time) to the Economic and Commercial Councillor of the Embassy of the People’s Republic of China to Namibia on 07 May 1997, the scope of the project was revised to consist of the preliminary planning of two pipelines, namely:
1. A pipeline from the Okavango River to the existing water supply network in the Cuvelai area to supplement any shortfalls in supply from the Kunene River, 2. A pipeline from the Okavango River to the unserved eastern part of the Ohangwena Region and the unserved north-eastern part of the Oshikoto Region.
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Water supply from the Okavango River to the Cuvelai area was to be considered in the light of a hydrological risk assessment on the supply to this area from the Kunene River (Calueque) in the first instance, and considering the expected future development of the eastern Ohangwena and the north-eastern Oshikoto Regions in the second, based on expected water demands up to 2020 in both instances.
The results of the assessments carried out were published in 9 volumes.
3.3.1.6.3 Hydrological Risk Assessment for the Cuvelai Area A hydrological risk assessment for the extent of the pipeline supply network in the Cuvelai area at the time was carried out considering human, livestock and industrial demand / consumption as primary water demand, to be supplied at a 100% assured yield, and irrigation demand / consumption considered as irrigation water demand, to be supplied at a 80% assured safe yield.
Water demand forecasts were prepared for the planning horizon to 2020; showing an expected water demand of 35 Mm3/a for the primary water demand to be supplied by the Olushandja, Ombalantu (Outapi), Ogongo and Oshakati purification plants, therefore for the portions for the Omusati, Ohangwena, Oshana and Oshikoto regions served via the pipeline network at the time. A further 30 Mm3/a was estimated for irrigation water demand, therefore totalling 65 Mm3/a to be supplied from the Kunene River.
The hydrological risk analysis showed maximum annual shortfalls in the year 2020; 11.47 Mm3/a with a peak monthly shortfall (in October) of 1.54 Mm3/m for the primary water demand and 30 Mm3/a with a peak monthly shortfall of 3.93 Mm3/m for the irrigation water demand.
3.3.1.6.4 Water Supply from the Okavango River Existing Areas: Pipeline 1 In order to reach a 100% assured safe yield for the primary water demand of areas served by the pipeline network at the time, the shortfall of 11.47 Mm3/a in the primary water demand, determined from the hydrological risk analysis, would need to be supplied from the Okavango River.
Unserved Areas: Pipeline 2 Water demands for 2020 of 2.36 Mm3/a in the then unserved eastern Ohangwena Region, consisting of domestic demand (1.36 Mm3/a) and livestock demand (1 Mm3/a) and water demands of 1.68 Mm3/a in the then unserved north-eastern Oshikoto Region, consisting of domestic demand (0.56 Mm3/a) and livestock demand (1.12 Mm3/a) would also need to be supplied from the Okavango River. In the latter cases, water supply was to be to Okongo in the Ohangwena Region at 4.68 Mm3 and 0.18 m3/s and to Okankolo in the Oshikoto Region at 1.95 Mm3 and 0.074 m3/s, including purification plant losses of 5% and pipeline losses of 10%, supplied over a 20-hour pumping day.
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3.3.1.6.5 Scheme Configuration The most favourable abstraction point in the Okavango River for both pipelines was considered to be upstream of Nkurenkuru, close to the junction of the D3407 and D3405 district roads between Mbambi and Simanya. An abstraction facility consisting of a diversion channel, a head bay, wet well and pump well was recommended.
Both above ground and buried pipelines were considered, with the latter favoured due to environmental and practical considerations.
A number of different pipe materials were considered with regard to pressure resistance, external load capacity, hydraulic roughness, chemical inertness, ease of transportation and construction and corrosion resistance, on which basis Glass Reinforced Plastic (GRP) pipe was selected as the favoured material. Pressure classes from 20 bar to 6 bar were recommended.
The first pipeline (to supply the shortfall in the existing network) was to consist of 316 km of 800 mm diameter GRP pipe from the Okavango River to Oshakati, with a design flow rate of 0.72 m3/s and flow velocity of 1.43 m/s (refer to Figure 3.9). A design pumping head of 75 m was required at the intake pump station, with 125 m pumping head required at each of 6 booster pump stations along the length of the pipeline.
The second pipeline, to supply unserved eastern part of the Ohangwena Region and the unserved north-eastern part of the Oshikoto Region, would consist of two portions. The first, from the Okavango River to Okongo, alongside the first pipeline, was to consist of 144 km of 450 mm diameter GRP pipe, with a design flow rate of 0.18 m3/s and a flow velocity of 1.13 m/s. The second portion, from Okongo to Okankolo, would consist of 105 km of 300 mm diameter GRP pipe, with a design flow rate of 0.074 m3/s and a flow velocity of 1.05 m/s (refer to Figure 3.10). For the first portion, 92 m of pumping head at the intake pump stations was required, with 150 m pumping head at each of two booster pump stations. In the second portion, 150 m pumping head at each of two further booster pump stations was required.
Both pipelines would follow the D3407 from the abstraction point as far as the junction with the C45 road to Okongo (the D3601 at the time) and then follow this road westwards to Okongo. The first pipeline would continue to the west to Omafo, thereafter turning to the southwest to Oshakati. The second pipeline would turn to the southwest at Okongo, as far as Oshidundumbe, thereafter turn to the west to Okankolo.
Horizontal centrifugal pumps were favoured over submersibles for the river intake pump station, as well as at the booster pump stations, in a 2+1 configuration in all instances. Due to the flat topography traversed by both pipeline routes, the booster pump stations were located at approximately equal intervals in both instances, with the first booster at chainage 5.5 km for the first pipeline and at chainage 10.0 km for the second.
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Figure 3.9: Proposed Route of the Okavango – Oshakati Pipeline (TIDI, 1998)
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Figure 3.10: Proposed Route of the Okavango – Okankolo Pipeline (TIDI, 1998)
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Power supply requirements were found to vary between 400 kW at the base and 710 kW at the booster pump stations for the first pipeline and between 155 kW at the base and between 110 kW and 200 kW for the booster pump stations for the second pipeline. Power demand varied between 320 kVA and 1,800 kVA for the various pump stations. Transformers, control and communications systems were provided for in the design considerations.
A construction period of 24 months for the pipeline to Oshakati and 18 months for the pipeline to Okongo and Okankolo was proposed. The costs were estimated to be N$ 662 million for the first pipeline to Oshakati and N$ 243 million for the second pipeline to Okongo and Okankolo.
3.3.1.6.6 Environmental Considerations The hydrological assessments determined that the Mean Annual Runoff (MAR) in the Okavango River at Rundu was 5,263 Mm3/a, with a maximum on record of 9,810 Mm3 in 1962/63 and a minimum on record of 2,260 Mm3 in 1971/72. The monthly values varied between 2,176 Mm3/m and 34 Mm3/m.
With a design capacity of 0.72 m3/s for the first pipeline, abstraction would be 6.4% of the lowest recorded flow of 11.1 m3/s. With a design capacity of 0.18 m3/s for the second pipeline, the combined abstraction rate would be 0.9 m3/s and therefore 8.1% of the lowest recorded flow in the river of 11.1 m3/s. Since, especially in the case of the second pipeline, water demand would be continuous, this would require a continuous abstraction from the Okavango River.
Based on 165 samples, silt concentration in the Okavango River was found to generally range between 10 mg/ℓ and 20 mg/ℓ, with a maximum value of 59 mg/ℓ, which was regarded as low and therefore not problematic for the operation of pump units and the pipelines.
In accordance with the ToR for this project, the preliminary environmental impact assessment focussed on the impact of the downstream environment in the Okavango River and the areas along the proposed pipeline routes.
Based on the stage-discharge curve, the proposed abstraction of 0.9 m3/s was found to affect the water level by between 1 and 2 cm in the driest period, and therefore unlikely to pose an “obvious impact” on the ecology downstream either in flood or dry periods. The environmental impacts identified relate mostly to construction activities, such as health risks arising from the influx of construction workers, noise dust and other pollution and the possible transfer of “schistomiasis”, “cercaria” and bilharzia via the raw water pipelines. Other risks included the potential land degradation resulting from an in-migration to areas not previously served with water. The establishment of an environmental management plan, monitoring measures and an organisation to carry out the monitoring were recommended.
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3.3.1.7 2004 Situation Assessment on Calueque Pump Station (NamWater, 2004) In 2004 NamWater completed a situation assessment of the water supply situation in the Cuvelai, including an assessment of the infrastructure at Calueque and the present and expected future water demands in the Cuvelai area. It was found that on the basis of increasing water demands for both potable and raw water (irrigation at Etunda), the peak month water requirements were expected to soon exceed the then capacity of the Calueque pumps. During times that both Calueque pumps need to be in operation, no standby capacity is available. On the basis of the evaluations carried out, it was recommended that new motors running at higher revolutions be installed at the Calueque pump station and that a third pump set be installed to act as a dry standby, although the financial feasibility of these measures was not investigated at the time (NamWater, 2004).
3.3.1.8 2009 NamWater Bulk Water Master Plan (LCE, 2009) In order to properly determine its future capital development and capital replacement expenditure requirements, NamWater, set out to compile an infrastructure master plan for their bulk water supply infrastructure across the entire country. The purpose of this plan was to draw up a framework within which investments in water supply infrastructure should be implemented over the coming years.
Due to the magnitude of the task, NamWater decided to undertake the work in phases, each phase covering a geographical grouping of existing water schemes. The first Bulk Water Master Plan (BWMP), the Water Supply Infrastructure Development and Capital Replacement Master Water Plan for the Central North Water Supply Area, was completed in September 2009. The Central North Water Supply Area is the term NamWater uses to describe the central portion of the Cuvelai area which is served with water from their network of canals, pipelines, purification plants, pump stations, reservoirs and pipelines.
The scope of this Bulk Water Master Plan included the following basic components:
A desk study, to obtain information from as-built drawings and planning, design and completion reports, A condition assessment to establish the condition of the various infrastructure components, Database and mapping to enter the data obtained from the first two components into an useable electronic format, An analysis of the historic water consumption of the Project Area and the identification of trends and other pertinent information, The preparation of realistic theoretical water demands for the current (2007/08) and future (2014/15 and 2029/30) scenarios, Capacity modelling and analysis to determine any shortfalls in supply between the current capacities and the expected future water demands, The identification of any shortcomings in the operation and maintenance of the various scheme components,
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Infrastructure development proposals whereby the identified shortcomings can be alleviated, Cost estimates for the above proposals, and A proposed expenditure timetable for the infrastructure developments.
The important outcomes of this Bulk Water Master Plan were the following:
1. A WaterCAD numeric hydraulic model was constructed to successfully simulate (model) the capacity of all NamWater’s bulk water supply infrastructure in the Cuvelai area, including some 739 pipelines extending over 1,359 km, 48 reservoirs and 37 pump stations, Proposals for capital replacement (the replacement of infrastructure, due to insufficient capacity or inadequate condition) and the development of additional infrastructure spanning the period 2009/10 to 2014/15 were prepared and costed. The total cost of the proposed investment over this period was N$ 252 million (2009 terms), 2. It was recommended that that NamWater investigate the security of supply to the CNWSA in greater detail, including: a. The abstraction rate from the Kunene River and whether additional storage should be provided at Calueque Dam or at Olushandja Dam, b. Determining what level of risk of shortfall in supply to the Cuvelai area would be acceptable, as this will in turn determine the volume of storage to be provided, and may also influence which location is more favourable (Calueque or Olushandja Dams).
3.3.1.9 2011 Combined Regional Rural Water Supply Development Plan (LCE, 2011) In keeping with the aim to increase the coverage of rural water supply, and in order to properly plan and budget to achieve this aim, the Directorate of Water Supply and Sanitation Coordination (DWSSC) in the MAWF prepared Regional Rural Water Supply Development Plans for the various Regions of Namibia. For the Cuvelai area, the DWSSC determined that a Combined Regional Rural Water Supply Development Plan (CRRWSDP) must be developed for the four regions in the northern part of Namibia, namely the Oshikoto, Ohangwena, Oshana and Omusati Regions. This is because the bulk water supply schemes in these regions, as operated by NamWater, consist of an integrated and interlinked pipeline network, which extends across all four regions, as well as the fact that the DWSSC distribution pipelines also extend across regional and constituency boundaries, which means that combining these four regions into one CRRWSDP would allow a holistic and comprehensive approach to be followed in the preparation of the Development Plan.
The scope of the consultancy services required for the CRRWSDP included the following:
1. The collection and scrutiny of available information relevant to the preparation and formulation of the development plan (regional poverty profiles, regional development plans, NamWater’s Master Water Plan, etc), 2. An investigation into and analysis of the present utilisation of water in the regions,
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3. An estimate of the future water demand of all present and potential future consumers within the given planning horizon, taking account of the likely impact of cost recovery on such demands, and with due regard for environmental impact and sustainability, 4. An overview of all existing water resources and of water sources with significant potential for further development, including an estimate of their possible contribution to meeting the expected future water demand, 5. A definition and evaluation of alternative solutions and, consequently, the prioritisation of the identified development options, 6. The preparation of preliminary designs and cost estimates for the upgrading of existing installations or for the development of new water supply infrastructure as the case may be, 7. An analysis of the affordability of systems to the communities, 8. An assessment of the institutional capacity of DWSSC to implement the priority solutions, including creation of the community capacity necessary for Community Based Management, within the given time frame and the resources available, 9. A comprehensive proposal for implementation based on solutions agreed upon in consultation with the DWSSC and representatives of the communities.
Numerous recommendations were put forward in this CRRWSDP, including those for the implementation of five new rural water supply schemes to increase the coverage of rural water supply. It was also recommended that a reassessment be conducted to determine whether, given the increase in private connections by individual households, the presently used unit consumption rate of 25 ℓ/c/d will still be sufficient in future.
3.3.2 Use of Surface Water Sources
3.3.2.1 Open Wells, Excavation and Pumped Storage Dams The earliest water supplies in the Cuvelai area were obtained by exploitation of the surface waters and from open wells. As water became scarcer, wells were dug, which were normally open excavations which were extended to keep pace with the water table as it receded in the dry winter months. Subsequent flooding caused the sides of these excavations to fall in and fill with silt, so repeated excavation was necessary (DWA, 1968).
In the drought of the late 1920s, the first excavated dams were constructed using hand labour. Many of these storage units had capacities of between 3,000 and 6,000 m3 and were the forerunners to providing carry-over water not only for the winter months but also for a succession of dry seasons (DWA, 1968).
In 1954 an intensive programme of expansion of the local storage works and the development of underground supplies was started. This was aimed at providing adequate local supplies to local communities and various urban growth centres. The principle of the “excavation dam”, which was open on at least one side to the local oshana, was retained, so that seasonal flow in the iishana filled these dams. The aim of these dams was generally to provide a 2-year supply, including for evaporation losses. By using earth-moving machinery the volumes of these dams could be increased to 20 – 30,000 m3.
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Palisades were erected to prevent cattle from trampling the sides. To provide suitable drinking water, simple sand filters leading to a well fitted with a hand pump was arranged. The fine local sand however had a very slow rate of percolation and these filters were not always satisfactory (DWA, 1968).
Figure 3.11: Typical Excavation Dam Layout (DWA, 1991)
The depth of excavation of these dams was limited by the shallow local saline water table. In some parts this is as shallow as 2 m, but generally more favourable conditions were sought and depths of 5 m were used. The location of these storage works was limited to iishana where the soil was dumped on two sides, allowing throughflow, and to certain pans where the dams were constructed with one side open to the pan (DWA, 1968).
The principle of creating storage was extended in the case of road construction, to the advantageous siting of borrow pits and the use of causeways to dam up the iishana. The capacities of these dams was mostly small, the most extreme case being the Oshakati Lake where a gross storage of 3 Mm3 was obtained. In the period 1954 – 56, 23 dams with sand filters were constructed, which had risen to over 300 of all types of dams by 1968 (after DWA, 1968). Of these, 180 had a capacity of 6,000 m3 or more (DWA, 1991).
Given the limitation of these excavation dams, on the depth of excavation by the shallow saline water table and on the capacity by high evaporation losses, the next step to securing storage was the construction of pump storage dams. To create pump storage dams, the excavated material was banked around the depression formed by the excavation to form a fully enclosed dam with the wall rising several metres above the oshana bed. An adjacent open sump was created to catch the local surface flow and to allow pumping into the dam. Water depths of up to 10 m were created in this way, which apart from more than doubling the capacity of the normal excavation dams also restricted the evaporation losses. Seepage through the raised banks of compacted fine clayey sand was found to be insignificant.
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Precast concrete facing slabs were used on the upper slopes of the walls to prevent wave erosion. By 1968, some 40 such pump storage dams have been constructed. About half of these were equipped with complete filter plants for supplying purified water to hospitals, schools and community centres (after DWA, 1968).
Figure 3.12: Typical Section through a Pumped Storage Facility (DWA, 1991)
However, the unit cost of water from these pump storage schemes was found to be 2 to 4 times more expensive than of schemes in other areas of the country, which necessitated the need for a cheaper and more efficient water supply system. Moreover, local runoff was not always reliable, and localised downpours could cause one oshana to flow and not others. The construction of collection furrows therefore evolved to provide greater security and capacity of supply, but these could not solve the problem of a lack of surface flow in dry years (after DWA, 1968).
It was found that by 1991, with the exception of those facilities which were controlled by the Department of Water Affairs, very little maintenance work had been done on the various excavation and pumped storage dams by the local administration during the past 10 to 15 years (This was most probably after the responsibility was handed over from the DWA to the Directorate of Works of the Administration of Owamboland (after DWA, 1990). Many dam basins had silted up and very few pump stations were still in operation (DWA, 1991).
3.3.2.2 Canals A solution to providing greater security of supply was found in the construction of a flood water collecting canal tapping a whole system of iishana. The first of these was the Oshakati canal which was started in 1960 and which later extended from the low point at Oshakati westwards as far as Outapi (Ombalantu), a distance of some 100 km. This canal was designed to fit in with a future system of bringing in Kunene River water and had an initial nominal capacity of 1 m3/s (cumec) (after DWA, 1968).
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This canal was initially unlined, although certain portions were later lined with concrete. At each oshana only the southern side was banked up and a spillway was provided such that initial runoff was diverted into the canal but that surplus flow was released down the oshana. This was found to perform very successfully and a 10 km branch canal was later constructed to Elim. A second main canal, also 100 km long, was constructed to the west of the Etaka between Eunda via Tsandi to Ongandjera. By 1968, some 250 km of canals, including collecting furrows, had been constructed (after DWA, 1968).
The 1968 Master Water Plan found that the provision of canals was preferable to that of pipelines and consequently envisaged an extensive network of canals, with a main artery from near Calueque to Oshakati, with further extensions and branch canals to serve a large portion of the central Cuvelai. This was implemented over a period of time and by 1991, some 179 km of canal had been constructed (DWA, 1991).
3.3.2.3 Pipelines To supplement the supplies in sites where the natural runoff was less advantageous, pipelines were constructed, including an initial 37 km long pipeline from Oshakati via Ongwediva to Ondangwa, forming an extension to the Oshakati canal system to overcome the adverse gradient of the land. Extension pipelines to the north (Oshigambo), south (Olukonda) and east (Onanjena) were proposed. By 1968, some 88 km of pipelines were in use in the Cuvelai (after DWA, 1968).
By 1978 some 447 km of pipelines had been laid in the Cuvelai for water distribution and pump stations and purification works were in place at 19 locations. Seven further pump stations without purification works were in use. The main distribution points, excepting Oshakati for local use, were identified as being Outapi (Ombalantu), Ogongo and Ondangwa, where larger purification works were to be located (Claassen and Page, 1978)
By 1991, some nearly 700 km of pipelines, 29 pump stations and 9 purifications plants were in use. In order to address the supply of water in an orderly manner, the Cuvelai was divided into eight different water demand zones (refer to Figure 3.13), with each zone chosen in such a way that at least one primary water carrier was available from where secondary distribution lines could be constructed to attain a more even distribution of water in that particular zone (DWA, 1991).
Due to the complexity of the pipeline network, it was divided into separate components as follows (DWA, 1991):
1. Kunene River – Olushandja 2. Olushandja – Okahao, 3. Olushandja – Ogongo, 4. Ogongo – Okahao, 5. Ogongo – Oshakati, 6. Oshakati – Ondangwa,
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7. Ondangwa – Oshivelo, 8. Ondangwa – Oshikango.
Figure 3.13: Water Demand Zones in the Cuvelai (DWA, 1991)
Following Independence, and the establishment of the Directorate of Rural Water Supply, now the Directorate of Water Supply and Sanitation Coordination, there was a rapid increase in water supply in the Cuvelai, with pipelines and associated projects funded by donor agencies and the fiscus. The extension of the pipeline water supply network in the Cuvelai is shown in Figure 3.14 to Figure 3.16.
Figure 3.14: Coverage of Bulk Water Supply Infrastructure in the Cuvelai in 1990
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Figure 3.15: Increased Coverage of Water Services in the Cuvelai Area 1990 to 2003
The recent (2009) extent of the water supply network in the Cuvelai is shown in Figure 3.16 (LCE, 2009).
Figure 3.16: Current (2009) Extent of the Bulk Water Supply Network (Canals, Pipelines and Pump Stations) in the Cuvelai (LCE, 2009)
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3.3.3 Groundwater in the Cuvelai Area
The construction of schools and clinics in the areas away from the main supply infrastructure was facilitated by the construction of concrete or cement-brick lined wells, relying almost entirely on groundwater. By 1968 some 50 wells equipped with hand pumps were in operation, with others under construction.
The first groundwater investigations in the Cuvelai were undertaken in the densely populated central area in 1927 (DWA, 1991). Seven boreholes were drilled in the central Cuvelai area in 1927/28. The results were discouraging as only saline water was encountered. Further drilling was undertaken in the period 1948 to 1953, again without success in the central zone, but with promise in the area to the east. An extensive drilling programme started in 1962, resulting in the sinking of some 250 boreholes. The majority of these were in the 50 – 150 m depth rage, others were up to 250 m deep, whilst 5 exploratory holes were drilled as deep as 650 m. Boreholes were generally more successful in the area to the east of the central Cuvelai, whilst those to the west were found to be more variable with regard to both yield and salinity (after DWA, 1968). Already by 1968 it was recognised that the areas to the east and west of the central Cuvelai could be supplied with groundwater, whilst this was not possible in the central zone.
By 1978 there were 165 boreholes of which 20 were electrically-driven, with the remainder wind-driven, hand pumps or monopumps (Claassen and Page, 1978). By 1991, this had increased to an estimated 400, of which 358 were installed with diesel pumpsets and 20 had been provided with windmills (DWA, 1991).
The 1991 Regional Master Water Plan identified that groundwater in the Cuvelai occurs in four major areas, as shown in Figure 3.17 (after DWA, 1991):
1. The Brine Lake Area in the central portion of the Cuvelai, where water from some boreholes was found to be more salty than sea water 2. The Eastern Area, where a success rate of 85% was found with boreholes yielding in the order of 2 to 5 m3/h with the water table at depths of 70 to 90 m, 3. The Western Area, where groundwater was found to be less reliable, in terms of the success rate of boreholes, and the variable salinity, 4. The Artesian Area, in the vicinity of Oshivelo to the southeast, where some boreholes provided high yields, although it was noted that little was known about the groundwater potential of this area at the time.
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Figure 3.17: Major Groundwater Areas in the Cuvelai (DWA, 1991)
3.3.4 Current Water Supply Situation in the Cuvelai
3.3.4.1 Pipeline Network As already noted, potable water is supplied via an extensive pipeline network in the central portion of the Cuvelai area. Both NamWater and the MAWF (via the DWSSC) are involved in the distribution of water via the pipeline network. All the canals, purification plants, reservoirs, pump stations and “bulk” pipelines belong to and are operated and maintained by NamWater. The “bulk” pipeline schemes are those which are used to transfer water in bulk (typically consisting of larger diameter pipelines, carrying larger volumes of water at higher pressure) and are generally greater than 160 mm in diameter.
The smaller, “rural” pipeline schemes, which typically constitute smaller diameter pipelines conveying smaller volumes of water at lower pressures for distribution purposes, are owned and operated by the DWSSC.
In many instances, the reservoirs and pump stations constructed by the DWSSC or its predecessor, the DRWS, have been handed over to NamWater. Where these were constructed prior to 1996/97, this infrastructure formed part of the assets transferred from the Department of Water Affairs to NamWater, with the establishment of NamWater. Subsequent to 1996/97, the MAWF and NamWater have come to an arrangement regarding the transfer to NamWater of such water supply infrastructure constructed by the MAWF. Some pipelines or pipeline schemes have been transferred to NamWater in the same manner, others not. Portions of some of the rural water supply schemes more recently constructed by the DWSSC are in the process of being handed over to NamWater. Those pipeline schemes not transferred to NamWater are generally those of diameters smaller than 160 mm, which are considered distribution pipelines as opposed to bulk transfer schemes (LCE, 2011).
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The delineation of responsibility between NamWater (upstream) and the DWSSC (downstream) normally occurs at a water meter installation, which is typically located as follows:
1. At an off-take from a bulk pipeline, which installation marks the start of the rural pipeline scheme, 2. At the outlet of a reservoir (either at ground level or elevated), 3. At the delivery side of a pump station.
3.3.4.2 Borehole Infrastructure The borehole-based water supply in the western and eastern parts of the Cuvelai has been implemented by the DWSSC and its forerunner, the DRWS; namely the sinking of the boreholes, the installation thereof and the construction of tank- and tap stands. The community served by each installation is typically responsible for the provision of fuel, if the borehole is equipped with a diesel pump, and the maintenance of the infrastructure.
3.4 BILATERAL RELATIONS REGARDING THE KUNENE RIVER
3.4.1 Bilateral Agreements
3.4.1.1 First Border Agreement, 1886 The importance of the Kunene River as a major water source was already noted by the early pioneers and the Ruacana Falls were often used as a landmark in the exploration of the area. The Border Agreement, which was signed on 30 December 1886 between the Governments of Germany and Portugal, aimed inter alia at securing a firm basis for so-called peaceful cooperation in the opening of Africa for the promotion of civilisation and trade (DWA, 1991).
In 1915 German South West Africa was occupied by the Union of South Africa and was declared a Class C mandate by the League of Nations in 1920. The Union of South Africa was appointed the Mandatory and became responsible for the Territory of South West Africa.
3.4.1.2 Second Border Agreement and First Water Use Agreement, 1926 Due to the ambiguity of the general terms of the Border Agreement of 1886 between the German and Portuguese Governments, and after Germany had lost its colonies in the First World War, a second Border Agreement was reached between the Governments of Portugal and the Union of South Africa, who respectively controlled Angola and Namibia at that time, on 22 June 1926. Article 2 of this Border Agreement defines a part of the international border between the Territory of South West Africa and Angola was the middle of the Kunene River, from the Atlantic Ocean eastwards to the Ruacana Falls. The border was subsequently demarcated and is recognised internationally as the border between Namibia and Angola. In terms of this definition, the international status of the Kunene River and the right of both countries to use water from the river was confirmed (after DWA, 1991 and KUNENERAK).
By virtue of being contiguous to both Namibia and Angola along its length from the Ruacana Falls to its mouth, and by virtue of flowing through the two countries successively, the beneficial use of the waters of the Kunene River cannot be denied to any of these countries (DWA, 1991).
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With the signing of the First Water Use Agreement (following the Second Border Agreement) between the Portuguese and South African Governments, on 01 July 1926, the premise was accepted that the floodwaters of the Kunene River Drainage Basin formerly flowed into the Cuvelai area, but that the inflow had decreased considerably due to the siltation of the old river courses. It was therefore agreed that the diversion of water from the Kunene River or humanitarian reasons and the benefit of Namibia could be allowed under certain conditions (DWA, 1991). This agreement gave the Union of South Africa “the right to use up to one half of the flood water of the Kunene River for the purposes of inundation and irrigation”. However, what is meant by “flood water” has never been clearly defined between these two countries (KUNENERAK).
3.4.1.3 Second Water Use Agreement, 1964 After the Union of South Africa became a Republic in May 1961, further Water Use Agreements were signed by the respective governments in 1964 and 1969 (the Second and Third Water Use Agreements respectively). The 1964 Agreement, signed on 13 October 1964 in Lisbon, concerned “rivers of mutual interest”, the “Cunene River Scheme”, setting out general principles for mutually beneficial “best joint utilization”, collaboration on the exchange of hydrological and other relevant data, mutual consultations regarding the execution of major hydraulic works affecting the interests of both states, joint study of the general plans for the development of water resources of each basin and negotiations in respect of concluding agreements (after KUNENERAK and DWA, 1991). Regarding the diversion of water for use in Ovamboland, Section 1 under Article II of this agreement noted: “the question of principle having been settled, the South African authorities must now submit a specific plan (including site, small dam. etc.) for the diversion and pumping of water from the Cunene”.
3.4.1.4 Third Water Use Agreement, 1969 A Third Water Use Agreement between the South African and Portuguese Governments was signed on 21 January 1969, also in Lisbon. This, more detailed agreement, aimed to achieve the following benefits:
1. The regulation of flow in the Kunene River, 2. The improvement of the generation of hydro-electric power at Matala, 3. Initial irrigation and the supply of water for human and animal requirements in the middle-Cunene, 4. The supply of water for humans and animal requirements in South West Africa and for initial irrigation in Ovamboland, 5. The generation of hydro-electric power at Ruacana.
Under Article 4.2 of this agreement [Works at Calueque], it was specified that “the quantity of water to be abstracted by means of the pumping scheme during any one week, shall be limited to one half of the natural flow of the river at the point of abstraction during that week, subject to a maximum pumping rate of 6 cubic metres per second” (Article 4.2.2).
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Article 4.2.5 further specified that “the pumping scheme shall be operated solely for the supply of water for human and animal requirements in South West Africa and initial irrigation in Ovamboland, under which conditions no charge shall be raised in respect of the maximum of 6 cubic metres per second”.
Under Article 2.2 of this Third Water Use Agreement, a Permanent Joint Technical Commission (PJTC) was established, to act in an advisory capacity, to study and report on matters relating to this agreement. Article 5.3 also required the PJTC to “revise the hydrological studies carried out by both countries” with regard to the abstraction rates allowed for under this agreement.
3.4.1.5 Fourth Water Use Agreement, 1990 Following the independence of Angola in 1975 and Namibia in 1990, the Fourth Water Use Agreement was signed between the governments of the People’s Republic of Angola and the Republic of Namibia in Lubango on 18 September 1990. This agreement endorsed the principles of the previous three agreements, and the parties agreed to:
1. Ensure the maximum beneficial regulation of water flow at Gove Dam, 2. Ensure the continuous operation and adequate maintenance of the water pumping works at Calueque and the diversion weir at Ruacana, 3. Allow the PJTC to evaluate the development of further schemes on the Kunene River in order to accommodate the present and future needs for electricity in both countries.
3.4.1.6 Fifth Water Use Agreement, 1991 The Fifth Water Use Agreement, being the most recent and the one currently in effect, was signed between the governments of the People’s Republic of Angola and the Republic of Namibia in Lubango on 24 October 1991. Pursuant to the investigations concerning hydropower provided for under the Fourth Water Use Agreement, under this Fifth Water Use Agreement it was agreed that:
1. A new hydroelectric scheme on the Kunene River “downstream from Ruacana, at the most suitable location that can be found in the Epupa Region or other location”, would be developed jointly, “if technical and economic feasibility studies include the environmental and ecological studies would advise implementation of the project”, 2. Representatives would be appointed to negotiate on behalf of the respective governments on all aspects related to the aforementioned.
3.4.2 Permanent Joint Technical Commission
3.4.2.1 Establishment of the Permanent Joint Technical Commission The Permanent Joint Technical Commission (PJTC) was established based on Article 2.2 of the Third Water Use Agreement of 21 January 1969, to act solely in an advisory capacity, to study and report on matters relating to the Third Water Use Agreement. It was particularly instructed to oversee the implementation of development projects on the river encompassing the construction of three dams, a power station, and a pumping station.
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This mandate was renewed in the Fourth Water Use Agreement of 18 September 1990 (KUNENERAK). In particular, the PJTC was instructed to oversee the implementation of development projects on the river encompassing the construction of three dams, a power station and a pumping station (after IWRMPJVN, 2010b and DWA, 1991).
As specified in Article 2.2 of the 1969 Water Use Agreement, the PJTC is to consist of “an equal number of members from each country, appointed by the respective Governments”, with the regulations under which the Commission will operate to be “subject to approval by both Governments”.
3.4.3 Terms of Reference of the Permanent Joint Technical Commission
Pursuant to Article 2.2 of the Third Water Use Agreement of 21 January 1969, a Terms of Reference and Constitution were drawn up for the PJTC. These ToR include (after KUNENERAK):
1. The revision of hydrological studies carried out by both countries, 2. Giving advice in regard to whether the works constructed in Angola by the South African authorities have been completed, 3. Submitting proposals to the two Governments concerning surveys, studies and investigations considered essential for the discharge of duties, 4. To assemble records and to initiate the collection of hydrographic data and of other hydrological measurements relating to the Kunene River and its tributaries including, as far as may be relevant, diversion and abstraction of water therefrom, 5. Undertaking expert evaluation of all hydrological data, 6. Considering and reporting on conformance to any agreed principles of the Agreement, 7. Organisation of technical supervision of any approved measures of joint interest, 8. Requesting special financial and technical assistance as it considers appropriate, 9. Carrying out studies at the request of either Government and advising on proposals for the further development of the water resources of the Kunene River basin in accordance with the principle of best joint utilisation with a view to water supply, irrigation, power development, flood control, reclamation and drainage, consideration of fish and wildlife, recreation and tourism and other beneficial uses, 10. Investigating, reporting and making recommendations to the two Governments on any question they may wish jointly or individually to refer to the PJTC, and 11. Exercising any other functions allocated to the PJTC by the two Governments.
3.4.3.1 Constitution and Structure of the Permanent Joint Technical Commission The Constitution of the PJTC specifies that it is to consist of six members, three from each country, at least one of whom shall be a professional hydraulic engineer. Members are to hold office for a period of three years and each government shall appoint one of its own members of the PJTC as Chairman of its delegation.
The current organisational structure of the PJTC is shown in Figure 3.18.
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Figure 3.18: Organisational Structure of the PJTC (KUNENERAK)
Since a large portion of the function of the PJTC is a focus on hydropower generation from the Kunene River, the position of Namibian Co-chair of the PJTC rests with the Permanent Secretary of the Ministry of Mines and Energy (MME) and therefore the person who fills that position.
3.4.3.2 Initiatives and Projects of the Permanent Joint Technical Commission The PJTC has several sub-committees which deal with other particular issues regarding the management of the basin, for example (KUNENERAK):
1. Task Force Calueque (TFC), 2. Baynes Committee (BC), 3. Committee on Bilateral Agreements, and 4. Committee on the Kunene River Basin Master Plan.
3.4.4 Kunene Transboundary Water Supply Project The Kunene Transboundary Water Supply Project (KTWSP) is a Southern African Development Community (SADC) Pilot Project under the Regional Strategic Water Infrastructure Development Programme (RWSIDP). This project covers areas in southern Angola and northern Namibia (the Cuvelai) and entails the development and rehabilitation of water supply and sanitation infrastructure for communities and towns along the border between the two countries.
Another important component of the project is to establish and build the capacity of a water utility entity in the Cunene Province in Angola to manage the scheme. The KTWSP is implemented by the Task Force Calueque, a sub-committee of the PJTC and is financed in part by the German Government through the Kreditanstalt für Wiederaufbau (KfW) and Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ), while the Governments of Angola and Namibia provide the balance of the funds (IWRMPJVN, 2010b).
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Specifically, the project aims to provide water to the towns of Ondjiva, Santa Clara, Namacunde and Omupanda in the Cunene Province of Angola, north of the border with Namibia, via the existing water supply network in Angola and Namibia. This will require upgrading several components of the existing water supply infrastructure, including the raw water intake and raw water pump station at Calueque, the Calueque – Mahenene Canal and the Omakango, Omafo and Oshakati pump stations, as well as the construction of a new pump station at Indangungu and 50 km of new pipelines, whilst NamWater will refurbish the water purification plant at Oshakati. The design and tendering for construction of these works is currently underway (VM, 2010/11).
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WATER RESOURCES AVAILABLE TO THE CUVELAI AREA
4.1 CURRENTLY USED WATER RESOURCES The water resources currently used in the Cuvelai area can be classified as follows:
1. Surface Water: a. The Kunene River, b. Surface flow in the iishana, 2. Groundwater, which is used predominantly in the western and eastern portions of the Cuvelai.
The currently known capacities of these resources are summarised below.
4.2 THE KUNENE RIVER
4.2.1 The Kunene River Basin
4.2.1.1 Introduction1 The raw water source for the entire central part of the Cuvelai Area is the Kunene River, from where water is abstracted at Calueque Dam in Angola. Also referred to as the Cunene, this river arises in west-central Angola, about 32 km north east of Huambo in the Sierra Encoco Mountains in Angola and flows southwards from the Angolan highlands to the border with Namibia, then turns westwards, forming the border between these two countries, until it reaches the Atlantic Ocean. The Kunene River basin covers an area of 106,500 km2, of which 14,700 km2 (13%) is located in Namibia and 95,300 km2 in Angola. The River is 1,050 km long and is one of the relatively few perennial rivers in this region, with a mean annual discharge of 5.5 km3 at its mouth (after LCE, 2009 and KUNENERAK). The location of the Kunene River basin in shown in Figure 2.12 and Figure 4.1.
The Kunene River basin covers an area where climatic and other conditions, vegetation and topography vary widely. In the upper reaches of the basin, rainfall is approximately 1,300 mm/a, decreasing to less than 100 mm/a in the lower reaches, whilst gross open water surface evaporation ranges from 1,700 mm/a in the upper catchment to 2,300 mm/a in the lower parts of the river close to the Atlantic Ocean. The river arises in the central highlands of Angola at elevations between 1,700 m and 2,000 m amsl east of Huambo, flows, over relatively flat floodplains in the mid-section of the river, to the rocky and arid areas in the lower reaches, which form the border between Angola and Namibia.
1 Unless otherwise specified, the information in this section is referenced mainly from the Kunene River Awareness Kit (KUNENERAK) which is an initiative of the PJTC.
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The upper plateau, known as the “planalto”, consists of a rolling eroded surface, which is well- watered and fertile and which has consequently become a densely populated area. This area also hosts the headwaters of other important rivers such as the Kuanza, Queve and Kubango (Okavango) and is therefore an extremely important land unit for Southern Africa’s regional hydrology (after KUNENERAK).
The Kunene River is important both for water supply and hydropower generation for both Angola and Namibia, and is one of 15 recognised transboundary river basins in the SADC region.
Figure 4.1: The Kunene River Basin (KUNENERAK)
4.2.1.2 Longitudinal Profile The longitudinal profile of the Kunene River, shown in Figure 4.2, illustrates the variation of the basin’s topography. Geographically, the river basin can be divided into three main sections: the Upper, Middle and Lower Kunene (refer also to Figure 4.3).
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Figure 4.2: The Kunene River Elevation Profile (KUNENERAK)
Figure 4.3: Sub-Basins of the Kunene River (KUNENERAK)
4.2.1.3 Climate Classification for the Kunene River Basin According to the Köppen- Geiger Climate Classification (refer to Section 2.2.2), the Kunene River basin is divided into three classes, shown in Figure 4.4, which roughly correspond to the three reaches of the river; the Upper Kunene, the Middle Kunene and the Lower Kunene.
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In the upper portion of the basin (refer also to Figure 2.1), the climate classification is Category C, denoting mild temperate climate, with the specific classification being humid subtropical (Cwb), implying a temperate climate with dry winters. Towards the south and east of the basin, the climate classification changes to Category B, which denotes arid and semi-arid climates where the precipitation is less than the potential evaporation. In the middle section of the Kunene River Basin, the climate is classified as semi-arid steppe (BSh), whilst in the lower reaches the climate is classified as a dry desert climate (BWh).
Figure 4.4: Climate Classification for the Kunene River Basin (KUNENERAK)
4.2.1.4 Ecoregions, Soil Types and Land Cover From the north to the south west, the river traverses six main ecoregions, from Angola Afromontane forest to Kaokoveld Desert, four main geological zones based on age, and different soil types. Overall, infertile soil groups cover more than 80% of the catchment.
Land cover in the basin is directly related to the prevailing climate and soil types. This varies from grassland and scattered bush on the highland plateau, to woodland and wet grassland in the middle reaches, to open woodland and bush further south, Mopane bush land and woodland to the west of Ruacana and almost bare ground in the desert near the river mouth.
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4.2.1.5 Precipitation and Evaporation The mean annual precipitation varies significantly across the basin, from approximately 1,300 mm/a in the upper reaches, decreasing to 20 to 100 mm/a in the lower reaches near the coast (refer to Figure 4.5).
Figure 4.5: Precipitation Across the Kunene River Basin (KUNENERAK)
Rainfall in the basin is seasonal, with a rainy season between October and March, although approximately 90% of the annual volume falls in a five-month period between December and April, with the main season occurring between February and March.
Evaporation rates, whilst high, also vary significantly across the basin. These rates are lowest in the upper catchment area (approximately 1,700 mm/a), high in the middle of the basin around Calueque, and around 2,300 mm/a in the lower parts of the river close to the Atlantic Ocean. Most of the total annual evaporation occurs between September and December, with rates between 300 and 350 mm/m, corresponding with a dry period across the basin, prior to the onset of the rainy season. The winter months of June and July have the lowest evaporation rates; around 180 mm/m.
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4.2.1.6 Upper Kunene Sub-Catchment The headwaters of the Kunene River are located on the crest of the Angolan Highlands along the northern divide which follows the “Luanda swell” which is an east – west orientated uplifted geological belt. Drainage to the south of this divide forms the Kunene River whilst drainage to the north is directed towards the Congo basin.
Figure 4.6: Upper Kunene Sub-Catchment (KUNENERAK)
The Upper Kunene is characterised by highlands with gentle rolling hills, separated by broad shallow valleys in the central Angolan Highlands, between an altitude of 1,800 m to 2,000 m at the source and 1,200 m up to the towns of Huambo and Matala. The first 330 km of the river have a relatively steep slope, averaging 1:1,000, with a number of rapids and steep sections. The main channel, approximately 100 m wide, is well defined with a bed of stones and sand, indicating rapid runoff and little sediment storage within the river system. The steep river slope also means that the river runs almost dry at the end of the dry season. This section has a number of permanent tributaries (refer to Figure 4.6).
Along the western divide of the Upper Kunene sub-catchment, lies an escarpment which drops steeply to the west and which forms a barrier to humid air moving in from the west and giving rise to typical relief rainfall over this northern part of the catchment.
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The Upper Kunene is characterised by open forests and savannah with shrubs. Human interference is evident, with riparian habitats showing signs of deforestation and the presence of introduced species.
4.2.1.7 Middle Kunene Sub-Catchment The Middle Kunene, from Matala to Calueque, consists of rolling hills in the northern areas, with the terrain becoming flatter towards Ruacana and the Namibian border in the south. The river has a flatter gradient than in the upper reaches, dropping from an altitude of 1,300 m to 1,000 m over 430 km. The river flows over Kalahari Sands with a low gradient, where the eastern bank is well defined, whilst the western bank has broad flood plains, up to 15 km wide, containing numerous lakes and lagoons. Within the Middle Kunene sub-catchment area, the river is fed by largely perennial rivers which drain wide floodplains.
The Upper and Middle Kunene areas belong to an ancient drainage system which was developed prior to the formation of the African continent. The Middle Kunene was originally an inland delta area, joining the Cuvelai channels into a lake which is now the Etosha Pan, similar to the present-day Okavango Delta.
Figure 4.7: Middle Kunene Sub-Catchment (KUNENERAK)
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Habitats in the middle reaches of the Kunene River change from open savannah with shrubs, alternating stands of dense close forest, to savannah associated with more arid areas and poorer soils.
4.2.1.8 Lower Kunene Sub-Catchment The relatively flat and slower flowing character of the Middle Kunene upstream of the Calueque rapids changes to a steeper profile in the Lower Kunene. Here the river has steep gradients (averaging 1:400), and over a distance of just under 385 km, drops nearly 1,200 m, which reach includes several spectacular waterfalls, the most important being the Rucana, Epupa and Kivale Falls. After the Calueque rapids, the floodplain ends abruptly and the river narrows considerably, with its character changing dramatically with a series of five rapids over 37 km to the Ruacana Falls.
Figure 4.8: Lower Kunene Sub-Catchment (KUNENERAK)
At the Ruacana Falls, the river turns sharply to the west, forming the border between Angola and Namibia. From this point onwards, the course consists of a steep descent to the coast through mountainous topography and semi-arid to arid conditions. Downstream of the Epupa Falls, the river morphology changes its character, cutting a deep gorge with several cataracts.
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From this point downstream, short seasonal streams, including the Otjindjangi (Marienfluss), occasionally enter the river on either side of the bank. The river then flows from the Baynes Gorge into the 70 km wide coastal Namib Desert, before emptying in the Atlantic Ocean.
The very different morphology of the river downstream of the Calueque Dam relative to that upstream, is due to the geomorphological development of the drainage system. The upstream catchment was originally an endoeric catchment (the main river outlet does not enter empty into the sea), when the upstream portion of the river flowed into the Etosha Lake, which was then permanent. At some point in time, the main flow broke through to the west where the Ruacana Falls are now located, and then cut a channel through to the sea. As the river gradually incised itself into the landscape, the flows to Etosha disappeared, resulting in this becoming the ephemeral Etosha Pan. As a result, the Lower Kunene is a young river, relative to the upper and middle reaches, and is characterised by steep gradients, rapids and a channel controlled by the bedrock.
Due to the arid and semi-arid conditions of the Lower Kunene, very little water in the river is contributed from the lower tributaries.
Habitats in the Lower Kunene evolve from dry steppe / savannah with stands of larger trees in the riparian zone, to specialist desert communities towards the coastal area. The wetland area of the Kunene River mouth, which is about 700 km away from the nearest permanent wetland, is an important staging area for birds and mammals.
4.2.2 Hydrology The Kunene River basin is regarded as consisting of three sub-basins or sub-catchment areas, the Upper, Middle and Lower Kunene, shown in Figure 4.3. The Kunene River has a catchment area of 89,600 km2, with a mean annual runoff of 6,012 Mm3/a at Ruacana (Pitman and Midgely, 1974).
4.2.2.1 Tributaries and Drainage The majority of the catchment of the Kunene River lies in the west of Angola, where rainfall is relatively unreliable and variable, which results in a large variation in flow in the river; flow volumes can differ as much as 14-fold between high and low years, whilst within a given year, the variation in river flow can be as much as 11-fold between the peak flow in April and the low flow in October.
The major tributaries of the Kunene River are (refer also to Figure 4.1):
1. The Que River, which with a length of 140 km, is the longest tributary in the dense river network of the Upper Kunene sub-basin, and which drains the south western part of the sub-basin, 2. The Chitanda River, which drains the eastern part of the Middle Kunene and has a length of 265 km,
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3. The Mucope River, which originates just south of Matala in the centre of the basin and which drains the central floodplain in the Middle Kunene, with a length of 190 km, 4. The Kaculuvar River, which with a length of just over 320 km, is the longest tributary of the Kunene River. This river originates near Lubango and drains the western part of the Middle Kunene, 5. The Otjindjangi River is an ephemeral river which originates in Namibia and which drains part of the Lower Kunene sub-basin, only flowing for part of the year during and immediately after rainfall.
There is currently no information available on the runoff of the tributaries and sub-catchments of the Kunene River (KUNENERAK).
4.2.2.2 Sediment The Upper and Lower Kunene sub-catchments have well-developed drainage systems, whilst the Middle Kunene sub-catchment is characterised by low gradients, annually flooded plains and natural deposition environments. By contrast, the Lower Kunene sub-catchment is a young river, characterised by steep gradients, rapids and a river channel controlled by bedrock. These differences have created two distinct sediment delivery systems: In the upper and middle part of the basin, fine-grained, suspended material dominates in combination with a chemically dissolved load. In the lower reaches, the river beds indicate a higher amount of sediment load (KUNENERAK).
4.2.2.3 Catchment Areas and Runoff The Hydrological Research Unit modelled the sub-basins of the Kunene River as single units, based on runoff records collected from gauging stations in the period 1961 to 1972 (Pitman and Midgely, 1974).
Approximately 40% of the runoff of the Kunene River is generated upstream of Jamba-ia-Mina, and approximately 75% to 90% of the entire flow of the Kunene River is generated in the Upper Kunene sub-catchment north of Matala. However, within the Upper and Middle Kunene sub- catchment areas, runoff decreases sharply from north to south, as shown in Table 4.1. Gauging station data, with records from 1962 to 1972, show an estimated runoff of 363 mm at Gove Dam, which decreases to 167 mm at the lowest section of this sub-catchment at Matala (Pitman and Midgley, 1974).
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Table 4.1: Catchment Area and Long-Term Mean Annual Runoff for Gauges on the Kunene River (1961 – 1972) (Pitman and Midgley, 1974)
Kunene River Area Mean Annual Runoff Gauging Station Sub-Catchment (km2) (Mm3/a) (mm)
Gove 4,900 1,777 363
Jamba-ia-oma 8,600 2,942 342 Upper Kunene Jamba-ia-mina 11,800 3,622 307
Matala 29,300 4,884 167
Folgares 37,300 5,280 142
Middle Kunene Matunto 43,500 5,519 127
Ruacana 89,600 6,012 67
No gauging stations and therefore no data is available for the Lower Kunene downstream of the Ruacana Falls.
4.2.2.4 Flows 4.2.2.4.1 Data Available Daily flow recordings (in cumecs) are available from the DWA, taken at Ruacana at the site location referred to as 2811M01, for the period 1961 to 1979. Very little data is however available for 1961. From 1962 onwards, anomalies in the flow rates are apparent for most of the years in this period, particularly over the last three or four days of each month, where the flow rates often increase or decrease by an order of magnitude from one day to the next, which is not possible. This data has not been used for further analysis.
Monthly volumes of flow in the Kunene River, as measured at Ruacana, are available for the period 1933/34 to 1987/88 from a previous study (LCE, 1992b).
NamWater provided daily flow rates taken at the location referred to as 2811M01 at Ruacana for the period 01 October 1999 to 30 October 2013. This record also contained data referred to as “historical” for the period 01 October 1995 to 31 September 2001. In this latter, “historical” period, a flow rate is provided for 31 September 2001, and for 29 February of every year, which is anomalous. For the most part, the data for the period 01 October 1999 to 30 October 2013 was analysed.
4.2.2.4.2 Flows at Ruacana and Calueque It is important to note that flows are measured at the weir at Ruacana, and not at Calueque. In order to derive flows at Calueque and overcome this shortcoming, a previous study used the flows recorded at Ruacana between 1933/34 and 1964/65 and adjusted these to exclude runoff upstream of the Gove Dam and allow for an average lag time of 1 month for different reaches of the Kunene River, to establish a relationship between the runoffs at Ruacana for the whole upstream catchment and the adjusted runoffs at Ruacana excluding the runoff upstream of Gove Dam. This relationship was then used to adjust the flows recorded at Ruacana for the period 1964/65 to 1987/88 to exclude the runoff upstream of Gove Dam and to derive flows at Calueque Dam for the period 1933/34 to 1987/88 (LCE, 1992b).
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For most of the analyses provided below, the recorded flows at Ruacana are used.
4.2.2.4.3 Daily Flow Rates at Ruacana The daily flow rate in cumecs (m3/s), as recorded at Ruacana and provided by NamWater, for the period 01 October 1999 to 30 October 2013, is shown in Figure 4.9. Whilst a pattern of a peak flow period around March and April of each year is discernable, it is also clear that the flow varies greatly from one year to the next. The largest flow rate recorded is 1,800 m3/s (11 March 2011) and the lowest flow rate recorded is 11.7 m3/s (16 November 2008).
Figure 4.9: Daily Flow Rates (m3/s) Recorded at Ruacana
4.2.2.4.4 Daily Flow Rates at Ruacana per Hydrological Year An overlay of the daily flow rates recorded at Ruacana for the October – September hydrological year (annual hydrograph) is shown in Figure 4.10, from which the annual variation in flow can be seen clearly. Overall, over the period, flow can be seen to increase from the beginning of December onwards, with a peak flow period of March and April, after which flow begins to decrease in May, with a low flow period of July – October / November.
In order to illustrate the large inter-annual variability in flow, Figure 4.11 shows the daily flows for the year with the largest annual volume of flow at Ruacana (2010/11: 15,565 Mm3/a) and the year with the lowest annual volume of flow at Ruacana (2012/13: 3,851 Mm3/a). The total volume of annual flow differs by a factor of four between these two years, whilst the peak flow rates (1,800 m3/s and 345 m3/s respectively) differ by a factor of over 5.
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Figure 4.10: Daily Flow Rates (m3/s) Recorded at Ruacana per Hydrological Year
Note: 1. Some years do not have a data value for 29 February.
Figure 4.11: Daily Flow Rates (m3/s) Recorded at Ruacana per Hydrological Year (Selected Years)
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For each year in the period 1999/00 to 2012/13, the mean (average) flow at Ruacana is higher than the median value (that value for which half the observations are greater and half smaller), which means that runoff or flow in the Kunene River is below the “normal” or average more often than it is above and that the flow is highly variable over time.
4.2.2.4.5 Monthly Volumes of Flow at Ruacana A comparison of the average monthly volumes of flow at Ruacana between the datasets available, being that from 1933/34 to 1987/88 from a previous study (LCE, 1992b) and that from 1999/00 to 2012/13 provided by NamWater (refer to Section 4.2.2.4.1) is shown in Figure 4.12.
Also shown is the minimum monthly flow required to allow the maximum agreed abstraction of 6 m3/s from the Kunene River, which at twice the abstraction rate, corresponds with 31.1 Mm3/m (refer to Section 3.4.1.4)2.
Figure 4.12: Comparison of Average Monthly Volumes of Flow (Mm3/m) at Ruacana from Different Periods
2 It should be noted that the allowable abstraction rate “during any one week, shall be limited to one half of the natural flow of the river at the point of abstraction during that week, subject to a maximum pumping rate of 6 cubic metres per second”. Firstly, weekly volumes are not available for the period 1933/34 to 1987/88 and hence the data has been analysed on a monthly basis. Secondly, the point of abstraction is at Calueque and hence the flow requirement applies there. However, flows are recorded at Ruacana and not at Calueque and inherent in this analysis is the “projection” of the Ruacana flows onto Calueque. Since the distance between these two points is only some 40.5 km along the river, and there are not major tributaries joining the Kunene River between these two points, the difference in flows is not expected to be significant.
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On average, the data for the period 1999/00 to 2012/13 is in the order of 50% higher than that from the earlier 1933/34 to 1987/88 period. It could not be ascertained whether this is due to a difference in measurement, calibration, climatic or other variation.
The average monthly volume of flow at Ruacana has always been greater than the twice the maximum abstraction rate of 6 m3/s (31.1 Mm3/m) over both periods for which data is shown. However, the difficulty of using averages is illustrated by the fact that for the earlier, 1933/34 to 1987/88 period, there are 12 months (5 in October, 5 in November and 2 in September) where the monthly flow has been less than 31.1 Mm3/m.
This serves to illustrate the variability of flow in the Kunene River, with regard to the abstraction from it, and illustrates the need for some storage provision of water to reduce the risk of low flow periods in the Kunene River. The flow records referred to above were furthermore analysed on a monthly basis. Due to the daily variation in river flow, occurrences where the flow is less than 12 m3/s could therefore occur for shorter periods within a month, particularly over a weekly period which is the time frame specified in the abstraction agreement, even though the overall monthly flow exceeds 31.10 Mm3/m, further underlying the need for storage provision (LCE, 2011).
4.2.2.4.6 Monthly Volumes of Flow at Calueque The average adjusted monthly volume of flow at Calueque (excluding runoff upstream of Gove Dam) between 1933/34 and 1987/88, as determined under a previous study (LCE, 1992b) is shown in Figure 4.13 (refer also to Section 4.2.2.4.2). Analysis of this data shows the occurrence of 48 months where the flow in the Kunene River was below 31.10 Mm3/m, equivalent to 12 m3/s. Nineteen of these occurrences took place in an October, and thirteen in both a November and a September, which months fall within the period of significantly lower flows before the typical onset of the rainy season, allowing for the lag time of flow reaching Calueque Dam. For the 55 year period analysed, in 26 years, being marginally less than half the period, the flow in the Kunene River was below the required 31.10 Mm3/m for at least one month in the year. This serves to highlight the need for storage should Namibia wish to abstract the maximum allowable 6 m3/s from the Kunene River.
A comparison between the average monthly volume of flow at Calueque (adjusted) and Ruacana is also shown in Figure 4.13. On the basis of the adjustment of the flows from Ruacana to Calueque, as carried out in 1992, the flows at Ruacana are on average 45% greater than the adjusted values at Calueque.
This serves to show that there is a difference between the flows at Calueque and Ruacana, and that should the abstraction rate be increased to the maximum allowable 6 m3/s at Calueque, further analyses may be required to possibly revisit the 1992 derivation as well as to provide a longer data record for flows at Calueque.
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Figure 4.13: Average Monthly Volumes of Flow (Mm3/m) at Calueque and Ruacana
4.2.2.4.7 Comparison of River Flow and Water Demand in the Cuvelai A comparison of the flow in the Kunene River, as recorded at Ruacana, and the water sales in the Cuvelai area is shown in Figure 4.14. In both instances, the monthly variation is shown, being the monthly total (either volume of flow or volume of sales) as the percentage of the annual total (volume of flow or volume of sales respectively). In the case of the water sales, the data is that of the billed sales provided by NamWater for the Cuvelai area (the pipeline network), including irrigation water, which is used as a proxy for the water consumption / demand in the Cuvelai area.
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Figure 4.14: Comparison of Flow in the Kunene River and Water Sales in the Cuvelai Area (Monthly Values as a percentage of Annual Totals)
Although the water sales (demand) in the Cuvelai area does not follow the variation expected, (for several reasons; refer to Chapter 6), this comparison nonetheless shows that the peak flow period in the Kunene River does not coincide with the peak water demand in the Cuvelai area. This difference is however not expected to place a limitation on the allowable abstraction rate for the near future, given that the required supply to the Cuvelai is much lower than the allowable abstraction limit, but this may change further into the future.
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4.2.3 Dams on the Kunene River
The main infrastructure constructed on the Kunene River are:
1. The Gove Dam, 2. The Matala Weir, 3. The Calueque Weir, 4. The Ruacana diversion weir and power plant.
In the Third Water Use Agreement of 1969 (refer to Section 3.4.1.4), the South African and Portuguese governments outlined the first phase of their joint development of the water resources of the Kunene River. This agreement outlined a plan to manage the river as an integrated system enabling the development of a hydropower project at Ruacana. This resulted in the construction of three major structures on the river in the 1970s, which comprise the Kunene River Scheme, namely the Gove Dam, Calueuque Weir and the Ruacana weir and hydropower plant, which are constructed on the Upper, Middle and Lower Kunene respectively. These structures were constructed in addition to the already existing weir and power plant at Matala in the Upper Kunene. The existing and proposed infrastructure on the Kunene River is shown in Figure 4.15. A summary of the characteristics of the dams constructed on the River is provided in Table 4.2.
Figure 4.15: Location of Existing and Proposed Infrastructure in the Kunene River Basin (KUNENERAK)
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Table 4.2: Summary of the Characteristics of the Structures on the Kunene River (KUNENERAK, DWA, 1991)
Dam or Weir Information Unit Cuando Gove Dam Matala Weir Calueque Dam Ruacana Weir Flow Flow regulation, Purpose Hydropower Hydropower Hydropower regulation water supply Upper Location Upper Kunene Upper Kunene Middle Kunene Lower Kunene Kunene Completion Date --- 19731 1954 (1976)2 1978 Earth Concrete Concrete embankments Wall type --- Earthfill gravity gravity overspill gravity and concrete structure central section Height m 7 58 16 17 --- Crest length m --- 1,111 1,035 2,300 --- Volume of wall Mm3 --- 4.537 ------(475)4 265 Full supply volume Mm3 --- 2,574 603 10 Max. capacity of m3/s --- 500 --- 5,0006 --- spillway Hydropower MW 1 607 39 --- 347 capacity Notes: 1. Completion date given as 1973 (DWA, 1991) and 1975 (KUNENERAK) 2. The dam was approximately 70% complete (KUNENERAK) when the contractor left the site in May 1976. The DWA then took over, and also left the site with the dam incomplete. 3. Storage capacity given as 60 Mm3 (KUNENERAK), Full supply volume given as 78 Mm3 (DWA, 1991), 4. Design volume of Calueque Weir (KUNENERAK) which is not available due to damage to the dam. The current storage capacity is estimated as 10 Mm3 (NamWater, 2004). 5. Storage capacity given as 20 Mm3 (KUNENERAK) and the full supply capacity as 26 Mm3 (DWA, 1991). 6. Design flood peak for 1:500 year return period (DWA, 1991). 7. Under construction, refer to Section 4.2.3.1.
4.2.3.1 Gove Dam Located in the upper reaches of the catchment, 120 km south of Huambo, the Gove Dam was the first component of the Kunene River Scheme to be completed in 1973, and thus facilitated the construction of the weirs at Calueque and Ruacana. The reservoir behind the dam has a storage capacity of around 2,570 Mm³ although the dam was seriously damaged during the war. The average annual flow of the river at Gove is about 1,600 Mm³/a (KUNENERAK).
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The primary design function of the Gove dam was to (after KUNENERAK):
1. Impound flood waters during the rainy season and thus regulate the flow along the entire Kunene River throughout the year to enable optimal power generation downstream at the Ruacana power station. The original intention of the Gove Dam was to provide a regulated flow of 80 m3/s at Ruacana, 2. Generate hydroelectric power for local consumption, particularly for the provinces of Huambo and Bié. An installed capacity of 60 MW will finally be available from February 2011, and 3. Store water and supply irrigation needs along the middle Kunene River in Angola.
The war in Angola prevented the Gove Dam from being used to regulate the flow of the Kunene as planned, and the structure was damaged in two attacks, with the second attack in 1990 causing particular damage. The Gove Dam and associated infrastructure is currently under rehabilitation to guarantee that it functions as originally foreseen, as a regulated flow in the Kunene River will not only benefit the Ruacana power station but will also be useful for example for the planned power stations at Jamba Ia Mina and Jamba Ia Oma (KUNENERAK)
4.2.3.2 Matala Weir The Matala dam is situated approximately 225 km downstream from the Gove Dam at the confluence of the Que River and the Kunene, on the edge of the Upper Kunene. The dam was the first major structure to be completed in the basin in 1954, and was renovated in 2001 with further work being carried out in 2010. It has a storage capacity of 60 Mm³ (KUNENERAK, 78 Mm3 DWA, 1991) with a mean surface area of 41 km². The scheme at Matala consists of a weir of over 700 m in length with movable gates, an inlet to the generators, an outlet and electrical mechanical equipment, appliances and power lines. The functions of the Matala dam are to:
1. Generate hydroelectric power, 2. Store water for domestic water supply and local development, and 3. Provide water for irrigation, with up to 10,000 ha of land available for irrigation, currently in need of rehabilitation.
The hydroelectric plant at Matala is the main source of electricity in southwest Angola, supplying the cities of Lubango, Namibe and Tombwa, with an originally planned capacity to generate 39 MW. This capacity was never reached, but work on the power plant which commenced in 2010 aims to ensure a production capacity of 40 MW.
4.2.3.3 Calueque Dam The dam at Calueque lies at the lower end of the Middle Kunene, approximately 540 km downstream from Gove Dam. Work on the dam started in 1972 and was 70% complete when work was abandoned in 1976 due to the war (KUNENERAK). Although the dam is partially functional, it is able to store considerably less water than the original design volume of 475 Mm³ - the current storage capacity is estimated to be only 10 Mm3 (NamWater, 2004).
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The Calueque Dam was designed with two main functions in mind (KUNENERAK):
1. To provide further regulation of the monthly flow of the Kunene River to enable optimal electricity generation downstream at Ruacana, and 2. To store water for bulk transfer for human and animal requirements and for irrigation in northern Namibia and Angola.
The Calueque dam is currently being repaired in order to fully function as foreseen, with an extension in its function planned with the addition of hydroelectric generators (KUNENERAK).
Further details of the Calueque Dam are provided in Section 5.2.1.
4.2.3.4 Ruacana Diversion Weir The Ruacana Diversion Weir is located some 40 km downstream from the Calueque Dam in the Lower Kunene. Construction of the diversion weir and hydroelectric power station at Ruacana commenced in 1971 and was completed in 1978, but only came into use in January 1980 when the sluice gates were closed for the first time. The main purpose of the Ruacana diversion weir is to provide a constant head of water in the river and divert the water through an 8 m diameter pipe for hydroelectric power generation.
Whilst the weir and inlet structures are located in Angola, the hydropower plant is in Namibia, and is Namibia’s main source of electric power, supplying up to 50% of the country’s needs.
The Ruacana scheme was constructed to make provision for four turbines, but only three were originally installed in the 1970s. Commencing with an upgrade of the scheme in October 2007, NamPower replaced the turbine runners of the original three turbines, to provide an additional 15 MW capacity and installed a fourth turbine with a capacity of 92 MW, to bring the combined capacity of the scheme up to 347 MW. These upgrades were commissioned in May 2012.
Due to the war in Angola, the Kunene River Scheme has yet to function in the planned integrated manner. The flow of the river has so far been poorly regulated by the Gove Dam and Calueque Weir, meaning power generation at Ruacana has been open to huge seasonal fluctuations, with spills during the wet season and very little generation during drought spells, as well as annual fluctuations.
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4.2.4 Water Quality
The Kunene River on the whole is relatively unpolluted and the water quality is considered to be good, with a low concentration of phosphorous and other nutrients, as the basin contains only limited irrigated agriculture and industrial activities. However, there are concerns regarding the deterioration of water quality and the lack of any basin-level assessment of water quality means that conclusive statements on water quality are difficult to make. Localised pollution is likely due to poor sanitation or untreated sewage outfalls from riparian towns and villages. Deforestation, uncontrolled burning and the application of non-conservational agricultural techniques lead to nutrient and soil runoff into the river, thus impairing water quality. Water impoundments in huge dams along the river increase the water temperature, which impacts adversely on dissolved oxygen and nutrient concentrations.
The mining and industrial developments opportunities of southern Angola have significant potential to cause harm to watercourses, including the Kunene River, through uncontrolled discharge of effluent (after KUNENERAK).
The Upper Kunene sub-catchment has a low sediment load.
Since the Middle and Upper Kunene sub-basins belong to the same well-developed, ancient drainage system, the water quality in the Middle Kunene is much the same as that in the Upper Kunene. Water quality in the Middle Kunene is characterised by calcium rich sediments and natural deposition environments. The water quality impacts of human settlements are fewer in the Middle than in the Upper Kunene, as the population density is lower.
Since the Lower Kunene is a younger river, with steeper gradients (refer above), the sediment load is higher than in the upper and middle reaches. Although the population densities are low in the lower reaches of the river, the riparian strip still sees pressure as a result of pastoralism, agriculture and the harvesting of forest products. This leads to degradation of the local ecosystems and impacts on water quality by contributing sediment and nutrients to the runoff.
4.2.4.1 Raw Water Tested by NamWater Based on information provided by NamWater, the Kunene River raw water is sampled in the canal system at the Bifurcation Flume, the Mahenene and Outapi Flumes (refer to Figure 5.11), though infrequently and irregularly. From the information provided, it appears that only inorganic determinants are tested, and not biological determinants.
The turbidity of the raw water is quite high; of the samples tested in 2013 and 2014, all show turbidity levels above 10 Nephelometric Turbidity Units (NTU), which is the threshold beyond which potable water is classified as being of Group C and Group D quality according to NamWater’s guidelines (both use the same threshold). By comparison, the Namibia Water Quality Standard (NWQS) requires treated surface water to have a turbidity below 0.5 NTU.
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The raw water quality meets the requirements for potable water quality, in accordance with the NWQS, according to the inorganic macro determinants for which results were provided by NamWater.
4.2.5 Proposed Developments in the Kunene River Basin
A number of developments, including hydropower installations and irrigation developments, are currently proposed in the Kunene River Basin, which will have an impact on the flow of the river (refer also to Figure 4.9). A summary of these is provided below (after KUNENERAK):
1. The Gandjelas Dam. This dam was built for irrigation purposes, and there are plans to fit the existing dam with a 2 MW electricity production capacity, 2. The Cuando dam in the very upper reaches of the catchment is fitted with a mini hydropower plant with four 250 kW turbines. This plant was non-functional for a long period of time but has recently been rehabilitated, 3. A proposed dam and hydropower scheme for 50 MW at the Jamba Ia Oma site, which is located approximately 50 km downstream from the Gove Dam, 4. A proposed dam and hydropower scheme for 126 MW at the Jamba Ia Mina site, which is located approximately 60 km further downstream, 5. A proposed dam an hydropower scheme for 465 MW at the Baynes site, which is located approximately 40 km downstream from the Epupa Falls, 6. There is significant potential to increase the area under commercial irrigation within the Angolan part of the basin and the current plans entail a total of 602,440 ha equipped for irrigation across the entire basin by 2025. The vast majority of this area, some 595,000 ha is located in the Middle Kunene. It is however acknowledged that if all of this potential was developed, the irrigation water demand (8 Mm3/a) (KUNENERAK) would exceed the annual average discharge of the river as measured at Ruacana (6 Mm3/a as shown in Table 4.1).
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4.3 SURFACE FLOW IN THE CUVELAI BASIN
4.3.1 Major Drainage Zones in the Cuvelai3
Whilst the Cuvelai and Etosha are names which characterise important expanses of surface water, most parts of the Cuvelai Basin and the Etosha Pan are ephemeral, thus holding water only sporadically. The occurrence, distribution and expanse of surface water in the Basin is seasonal, depending on where rain has fallen. Local, heavy rains in the Namibian part of the Cuvelai Basin generally causes localised flooding, whilst widespread flooding (efundja) is usually due to extensive heavy rain in the higher altitude and higher rainfall areas upstream and to the north in Angola. The presence of surface water is normally short-lived, as this water evaporates or percolates away over weeks or months, depending on the depth of water and the permeability of the soils (Mendelsohn et al., 2013).
Although the flatness of the terrain, the sandy nature of the soil and the ephemeral flow in the Basin generally results in poorly developed drainage systems, with the exception of the Kunene River, five marked drainage patterns were earlier identified in the Basin (DWA, 1991). More recently, 9 drainage areas have been identified in the Cuvelai Basin, as shown in Figure 4.16 below, which make up the Cuvelai system. All these drainage systems flow south from areas of higher elevation and rainfall in Angola, converge on the Omadhiya Lakes eventually the Etosha Pan.
The drainage zones function and flow in different ways, each with its own characteristics and patterns of water flow. Water flows regularly in the northern zones of the Iishana, Mui River, Cuvelai River, Cuvelai Delta and Central Drainage Zones, and the Cuvelai River is perennial up to the village of Evale. Water flows only rarely, and over short distances in the eastern zones. With the exception of Etosha Pan itself, all surface water in the Saline Pans and Central Pans Zones is from localised rainfall.
Water in the Cuvelai River, Mui River, Cuvelai Delta and Central Drainage Zones is largely fresh, since the flows are relatively rapid. Compared with those in the Iishana Zone, the channels in these zones are also much narrower and line with tall trees. Soils in the channels of the Iishana Zone are very saline, resulting from the high rates of evaporation from the broad waterways. Once the main flows drop and later stop, large areas of water remain standing in the channels and then gradually disappear through seepage and evaporation, leaving behind salts in the surface soils. As flow rates decrease from north to south, so also the salinity of the surface soils increases.
3 Unless otherwise specified, the information in this section is referenced mainly from the Profile and Atlas of the Cuvelai – Etosha Basin (Mendelsohn et. al., 2013).
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Figure 4.16: Major Drainage Zones in the Cuvelai Basin (Mendelsohn et al., 2013)
4.3.1.1 Mui and Cuvelai River Zones The Mui and Cuvelai Rivers provide the only perennial sources of water to the CEB, since they originate in areas which receive an average of about 900 mm per annum of rain in Angola. However, the distance which each river carries water down and into the network of iishana depends on how much rain has fallen. The northern reaches of the Cuvelai River are well- defined, with granite rocks lining the river banks, in contrast with the other drainage lines in the Basin which flow across alluvial or wind-blown sediments.
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Further south, the Cuvelai and Mui Rivers cease being single streams of flow and branch out into a myriad of very narrow, branching and interconnected channels. The Mui River fans out along the western edge of the Delta, whilst the Cuvelai fans out at the town of Evale, some 200 km north of the border. Flows from these channels eventually merge in the iishana with the water from the Iishana Zone to the northwest. In years of exceptional rain, the Caundo River may flow south to Nehone and beyond, with its waters also combining with those emerging from the channels of the Cuvelai Delta.
4.3.1.2 Calemo-Caundo Rivers Zone While parts of the catchment areas of the Calemo and Caundo Rivers (as well as those in the Eastern Sand Zone) drain areas of high rainfall in Angola, these rivers and their tributaries overlie extremely permeable Kalahari Sand. This is particularly the case in the eastern-most area. Following heavy rain, these rivers may flow for some distance, but as a result of the permeable soils, the water soon seeps into the ground.
The fossil river courses in the east and southeast, such as the Niipele River, were formed during much wetter periods, when water flowed much further than it does now.
4.3.1.3 Eastern Sand Zone Unlike the ephemeral rivers in the Calemo-Caundo Zone, the few remaining drainage lines in the northern Angolan part of the Eastern Sand Zone have extremely wide margins of grassland. These are important dry season grazing areas for the farmers in the area.
Away from these drainage lines and the many isolated pans which are found in a broad swathe to the north and south of the Angola – Namibia border, the entire landscape of the Eastern Sand Zone is dominated by tall Kalahari sand woodland. The numerous pans perhaps date from older, wetter periods. Some of these now fill with water after heavy local rains, but this water does not last long. These pans also provide the only soils suited to crop growth in this Zone and therefore all resident farmers live close to the pans.
4.3.1.4 Central Drainage Zone South of the converging flows of the channels of the Cuvelai Delta, several larger channels carry water due south down the Central Drainage to Ondjiva and Namacunde in Angola, Engela, Endola, Oshakati and Ompundja in Namibia and finally to the Omadhiya Lakes. Compared with the channels in the Iishana Zone, those of the Central Drainage Zone are narrower, generally lined with tall trees and the soils are much less saline.
Flows in these channels are also much more rapid than those in the shallower Iishana Zone channels, which is why there is less evaporation and salt accumulation in the Central Drainage Zone.
In years of abundant rain, the cumulative and convergent flows may cause significant flood damage to large areas between Ondjiva and the Omadhiya Lakes. Waves of flood water take several weeks to flow between Evale in Angola and Oshakati, a distance of some 200 km.
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4.3.1.5 Iishana Zone The Iishana Zone is approximately 140 km wide and 180 km long from north to south. Flows down the iishana are often erratic, starting and then stopping, only to start again when rain falls locally or upstream. While the iishana generally flow from northwest to the southeast, interconnecting channels often cut southwards. Unlike the narrow rivers and tributaries of the Mui and Cuvelai Rivers and channels in the Central Drainage Zone, the iishana are generally broad, many of them several hundred metres wide. The channels are also extremely shallow and flat, so that elevations between the iishanaand the surrounding higher ground differ by less than 10 m. The ridges of the channels are generally higher on the western side than on the eastern side, as a result of the prevailing winds from the east blowing sediments from the channels up onto the higher ground. Soils in the higher areas are finer on their eastern than western flanks, where there are often extensive patches of Kalahari Sand, most likely due to the effects of deposition of fine sediments by the easterly winds. Similar effects are seen around the pans on the Eastern Sand Zone.
The channels are also broader in the north than in the south, where they are more interconnected. The higher areas between the iishana are better suited to crop growing and are therefore also more densely populated. However, the salinity of the soils increases to the south, and hence population density decreases.
Compared with the Central Drainage Zone, widespread or substantial flood damage is rarer in the Iishana Zone.
The most southerly oshana, the Oshana Etaka has its origin near Calueque and just after entering Namibia, is impounded in the Olushandja Dam. The Etaka Canal was excavated alongside this natural watercourse.
4.3.1.6 Central Pans Zone To the east of the network of narrow channels in the Central Drainage Zone is a large area where surface waters only collect as a result of local rain, when tens of thousands of small pans form, many smaller than one hectare.
Most of the pans are isolated from those adjacent, whilst some pans form along ancient, narrow drainage lines established during wetter periods. A similar landscape sometimes develops after good rain in the northern part of the Saline Pans Zone. Channels of the Central Drainage Zone do not reach Ondangwa, which therefore does not suffer from the kind of flood damage that Oshakati does.
The Omadhiya Lakes to the south are a series of extensive, shallow grassy pans that merge into large bodies of water during periods of flooding. At these times, water from the lakes are mainly filled by local rain and by inflows from the channels of the Iishana and Central Drainage Zones. In addition, the Oshana Etaka (Etaka Canal) provides a separate source of water which first fills Lake Oponono before spinning eastwards into the main complex of lakes.
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The biggest lakes are Onamagwena, Uulidi, Oponono and Oshituntu. Water levels in the lakes are highest in March and April at the end of the summer rains, after which the levels drop rapidly as a result of evaporation. In most years, the lake areas are largely dry by November or December, particularly after the hot, windy months of September and October. As the water levels drop, the salinity increases and may reach 10 times the concentration of sea water. Thick layers of soft mud develop beneath the surface.
The area of inundation of the Omadhiya Lakes varies from year to year, with a maximum extent of flooding of approximately 7,500 ha, which is five times greater than the approximately 1,500 ha which is flooded almost annually. The lakes provide water for grazing cattle as well as substantial numbers of fish which are harvested, dried and then sold in the major towns.
4.3.1.7 Saline Pans Zone Over the last several million years, salts dissolved and carried in the water from the northern parts of the CEB to the south, have been deposited after evaporation. The southern reaches of the iishana drainage lines therefore consist of extremely saline soils and salt pans where the soils have been scoured out by wind. Cattle farming is the only viable agriculture in this zone, with many of the animals brought into this area for seasonal grazing in the winter months. Few people are therefore resident in the Saline Pans Zone in the southern part of the Cuvelai Basin.
The most well-known and prominent of these pans is Etosha, which covers some 4,812 km2. During years with strong flows down the Ekuma River from the Omadhiya Lakes, Etosha Pan becomes a lake with water up to 10 m deep in places. The Pan also receives occasional flow from the Omuramba Owambo which enters Fischer’s Pan at Namutoni. All the water which enters Etosha evaporates since there is no outlet from the Pan, which is the lowest point in the CEB, and the pan floor has an impermeable layer of clay which prevents water from seeping into the ground. Strong easterly winds steadily remove fine sediments from the surface of the Pan during the dry season, thus maintaining it as a local depression.
None of the smaller pans in this Zone receive inflows from the Cuvelai, even though some of them cover thousands of hectares. These small pans thus only hold water after heavy rains have fallen locally.
4.3.2 Floods in the Cuvelai System
4.3.2.1 Impact of the Floods In recent years the Cuvelai Basin has experienced serious flooding, which has caused the loss of human life, homesteads, crops, livestock and infrastructure, such as roads and canals. Substantial flooding occurred in 2007/08, 2008/09 and in 2010/11. Some flooding also occurred in 2009/01 (Mendelsohn et al., 2013).
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Figure 4.17: Flooding the Cuvelai Area
The most recent serious floods, in 2009, are estimated to have caused N$ 1.75 billion worth of damage and loss to the public and private sectors, equivalent to 1% of the Gross Domestic Product of Namibia (GRN, 2009). The agricultural sector is estimated to have lost 70-80% of the crop production in the six regions affected by these floods (Ohangwena, Omusati, Oshana, Oshikoto, Kavango and Zambezi Regions).
The 2009 floods affected 74.4% of the population in the Ohangwena, Omusati, Oshana and Oshikoto Regions, displacing 21,282 people and causing 102 deaths. In these four regions in the Cuvelai area, 26 health facilities (5 closed), 292 schools and 84,333 pupils were affected, an estimated 49,992 ha of crop fields were damaged and 9,985 livestock lost (LCE, 2011).
Although the efundjas have in recent years caused widespread disruption and impacted negatively on peoples’ lives and businesses, the seasonal flooding of areas of the Cuvelai Basin however provides vital resources to this area, including surface water. Surface water is widely used for livestock watering, when available, in order for farmers to save on purchasing water via the pipeline network.
In the Omusati Region for example, some livestock water points on the rural water supply pipeline schemes are known to be locked by the community once water is available in the iishana, and only opened in the late winter once the iishana have dried up (LCE, 2011). Substantial numbers of fish which move southwards with the flood waters also provide an alternative source of protein and income when harvested.
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4.3.2.2 Previous Flow Assessments The 1968 Master Plan reports on assessments of the flow in the Cuvelai at Oshakati over the preceding 27 seasons, noting that prior to 1955, such assessments were purely estimated orders of flow, but subsequently actual measurement was attempted. The resulting flow categories and respective occurrences are shown in Table4.3.
Table 4.3: Flow Categories and Occurrences in the Cuvelai (DWA, 1968)
Order of Magnitude of Flow No. of Flow Category (m3/a) Occurrences
Nil 0 10
Very Weak 100,000 2
Weak 500,000 3
Normal 5,000,000 4
Good 15,000,000 3
Very Good 50,000,000 3
Exceptional 100,000,000 2
A wide variation in seasonal flow is seen, in view of which, any assessment of a mean annual runoff has little significance. Of considerable importance however, is the fact that in nearly 40% of the seasons, no flow whatsoever was registered. If the no flow and “very weak” (occasions when only local runoff occurred) occurrences are excluded (disregarded as “flow” events), it can be seen that flow in the Cuvelai was found to occur only approximately 55% of the time. Seasons of very good rainfall, resulting in good to exceptional flow, seldom have a regular occurrence (after DWA, 1968).
4.3.2.3 Updated Flow Assessments One of the aims of this Study was to assess recent data pertaining to the flows in the Cuvelai, given the relatively recent occurrence of severe floods in 2007/08, 2008/09 and in 2010/11 (a quantative assessment).
Flow data pertaining to the Cuvelai was provided by the Directorate of Hydrology in the DWAF. However, this data shows isolated measurements at a variety of locations, over limited and isolated periods of time. This data is neither complete and consistent enough, nor available at a sufficient number of locations, nor over a long enough period of time to allow a meaningful analysis of the flows in the Cuvelai system.
A qualitative assessment is available on the basis of flood levels / events being classified as “none”, “small”, “medium” or “major”, as shown in Figure 4.18, which clearly shows the recent “major” flood events of 2008, 2009 and 2011 (these events occurred in the calendar years of 2008, 2009 and 2011 shown in Figure 4.18). Although several “major” events have occurred in recent years, the variability of these events is also well illustrated in this figure.
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Figure 4.18: Flood Levels in the Cuvelai (Mendelsohn et al., 2013)
4.3.3 Potential use of the Surface Flow in the Cuvelai
The variability of the flows in the Cuvelai and the very flat terrain, resulting in high surface area to volume relationships for impoundments, and therefore high evaporation losses, are why previous assessments found the construction of large dams, and even large excavation or pumped storage dams in the Cuvelai unfavourable (refer to Section 3.3.1). This is also one of the major drivers behind the expansion of the pipeline network serving the central portion of the Cuvelai area.
A further concern regarding the utilisation of surface flows in the Cuvelai is that of pollution of the water resulting from oils, grease and petroleum products washed into the iishana from runoff from urban areas, as well as from the flooding or overflow of gravity sewer systems and oxidation ponds.
Surface water in the Cuvelai system is a valuable natural resource, used for livestock watering for as long as water is available in the iishana. In the Omusati Region for example, some livestock water points on the rural water supply pipeline schemes are known to be locked by the community once water is available in the iishana, and only opened in the late winter once the iishana have dried up (LCE, 2011). This can significantly reduce the potable water demand via the pipeline network in the months following a good rainy season. The floodwaters also carry down large numbers of fish, and where ponded in the iishana, allow bullfrogs to congregate and breed, both of which are harvested as a source of protein (after Mendelsohn et al., 2013).
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4.4 GROUNDWATER IN THE CUVELAI AREA
4.4.1 Introduction
4.4.1.1 Technical Cooperation Project Between Namibia and Germany As part of the technical co-operation between Namibia and Germany, the Government of the Federal Republic of Germany provided financial and technical support through the project “Groundwater for the North of Namibia” executed by the Ministry of Agriculture, Water and Forestry (MAWF) and the Federal Institute for Geosciences and Natural Resources (BGR). Phase I of this initiative commenced in January 2007 and was completed in the first half of 2010. Phase II is currently running and is expected to be complete in May 2014.
The project activities are intensely linked to the DWAF-GTZ project “Integrated Land and Water Management in the Cuvelai Basin”. The study is based on a comprehensive desk study carried out for the DWAF, which summarised all previous findings on the groundwater potential and demand situation in the Cuvelai-Etosha Basin (LCE, 2011 and BIWAC, 2006).
The goal of this project is “to improve access to safe drinking water and the project objectives are to provide well founded information concerning the groundwater resources in the Cuvelai- Etosha Basin (CEB) as a basis for Integrated Water Resource Management (IWRM).” The ongoing investigations and their resulting outputs have to be converted into an applied management of the groundwater resources.
The technical tasks of the project are divided into three main areas of focus:
The delineation of freshwater yielding groundwater bodies in the CEB to provide access to safe and sustainable water resources, The development of a national groundwater information system to enhance and support management procedures and decision processes, The development of a decision support system for water resources information management in the CEB and combination with a numerical groundwater model for pilot- areas.
4.4.1.2 Information Compiled from Various Sources The information in this section is compiled from various sources, though is primarily based on the analysis of the groundwater supply and quality situation in the Oshikoto, Ohangwena, Oshana and Omusati Regions in the Cuvelai Basin as part of the Combined Regional Rural Water Supply Development Plan (CRRWSDP) (LCE, 2011). This information was based on the collection of data from a hydrocensus field investigation (DWA, 2007-2008) and that contained in the existing DWAF groundwater database (GROWAS). Information from recently drilled boreholes (at the time) was added as well.
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Information provided by the abovementioned DWAF / BGR project has also been used. One of the aims of the DWAF / BGR investigation was to provide maps, shown below, which indicate groundwater quality, thus indicating where it is possible to use groundwater as a safe water source for human or livestock consumption and where other water supply options should be found.
4.4.1.3 Groundwater in the Cuvelai-Etosha Basin Groundwater in the Cuvelai-Etosha Basin is found in a complex system of stratified aquifers containing fresh and / or saline water (sometimes exceeding the salinity of sea water). No consistent system regarding the spatial distribution of fresh and saline water has been established, and the distribution of the depths and potential yields of the different aquifer layers is only known locally. The intention of the DWAF – BGR Groundwater Project (DWA/BGR) was to investigate the distribution of fresh and saline groundwater and to determine the characteristics of the aquifers within the Cuvelai-Etosha Basin by a combination of geophysical and hydrogeological methods. This project concentrated on the two main target areas, i.e. the freshwater bearing KOH2 (the Ohangwena II) aquifer in the transition zone at Eenhana- Okankolo and the possible freshwater aquifer below the saline KOM aquifer in the Omusati Region. This BGR project was sub-divided into the following components:
Database Upgrade and Update: All available data sources for groundwater related information was systematically screened and entered into the database. The existing groundwater database was upgraded in two phases. The final phase will be to connect the database onto the internet to make it possible for the public to download any data required by them, Hydrocensus: A hydrocensus delivers information about existing boreholes, the current usage of the groundwater, irrigation activities and further relevant information. The hydrocensus and other field activities was utilised as a public awareness campaign and as a source of information for the public, Geophysical Measurements: Deep-penetrating, surface based geophysical measurements (e.g. time-domain soundings (Transient Electro-Magnetic (TEM) field surveys), borehole logging) was undertaken over target areas, selected on the results of the desk study and the hydrocensus, to provide information about the distribution of fresh / saline water aquifers down to a depth of approximately 400 meters, Drilling Test Boreholes: Test boreholes were to be drilled and geologically logged. Hydraulic tests and geophysical borehole logging were to be undertaken to provide geological and hydrogeological data essential for constructing a conceptual model of the area. Some of these boreholes will be used to upgrade the present groundwater monitoring network, Water Quality Survey: A detailed survey and analysis of groundwater quality, that included the sampling of all newly-drilled boreholes and selected boreholes identified during the preceding work, was to be executed. Some water samples were also to be used to do isotope analyses in order to determine the age and genesis of specific groundwater layers,
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Conceptual Model: Using the data collected during the previous steps and based on the fact that no long-term groundwater level monitoring data currently exists, a preliminary conceptual groundwater model is to be established to deliver a sound reflection of the actual hydrogeological conditions in the area.
4.4.2 Hydrogeology All the groundwater within the Cuvelai-Etosha Basin (CEB) flows towards the Etosha Pan, which is the area of lowest elevation in the basin. Three main groundwater flow systems can be distinguished within the CEB:
1. Groundwater recharged in the fractured dolomites of the Damara Sequence, which form the southern and western rim of the basin, flows north- and eastwards and feeds the aquifer system of the Karoo and Kalahari sequences. However, a major part of this north / eastbound groundwater flow is shallow, and this discharges through numerous springs along the southern margin of the Etosha Pan, where it evaporates rapidly. These aquifers are mostly outside of the Cuvelai area as defined for this Study, but somehow contribute to the recharge of other aquifers, 2. A deep-seated multi-layered Kalahari Aquifer is recharged in Angola and groundwater flows in a southerly direction towards the Etosha Pan and the Okavango River, 3. A shallow Kalahari Aquifer (formerly described as the brine lake area) superimposes both previously described aquifer systems in the central part of the CEB. The mainly saline groundwater originates from regular floods in the Cuvelai drainage, which has its headwaters in central Angola.
Furthermore, six main aquifer systems can be distinguished within the CEB, which are characterised by differences in geology, chemistry, patterns of flow, types of confinement and depths, namely:
1. The Otavi Dolomite Aquifer (DO) located on the western and southern rim, 2. Followed in the north by the Etosha Limestone Aquifer (KEL), 3. The Oshivelo Multi-layered Aquifer (KOV) in the eastern area, 4. The Ohangwena Multi-layered Aquifer (KOH1 and KOH2) in the north-eastern parts, 5. The Oshana Multi-layered Aquifer (KOS) covering the area of the Cuvelai drainage system, and 6. The Omusati Multi-zoned Aquifer (KOM) situated in the west adjacent to the KOS.
The schematic map in Figure 4.19 is a first attempt to provide an overview of the location of the aquifer systems within the intra-continental CEB. The extent of most of these aquifers is not yet properly defined and some aquifers intermingle or overlie / underlie others (e.g. KEL on top of DO or KOS on top of KOH).
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Figure 4.19: Location of the Main Aquifer Systems in the Cuvelai Area (BGR)
The known sub-aquifer-systems are summarised in Table 4.4.
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Table 4.4: Aquifer Names and related Geological Formations
New Former Group Name of Aquifer / Aquitard Sequence Formation Abbreviation Abbreviation (Subgroup) Ombalantu., Beiseb, Olukonda , Andoni , Etosha Kalahari Sequence Aquifer (undifferentiated) K N/A Limestone M., Recent Discontinuous Perched Aquifer KDP DPA Recent Etosha Limestone Aquifer KEL UKAEL Andoni (Etosha Limestone Member) Oshivelo Multi-layered Aquifer (undifferentiated) KOV N/A Ombalantu, Beiseb, Olukonda, Andoni Aquifer 1 KOV1 UKAAN Andoni . Aquifer 2 KOV2 OAAAN Andoni, Olukonda. Kalahari Oshana Multi-layered Aquifer (undifferentiated) KOS N/A Ombalantu, Beiseb, Olukonda, Andoni Aquifer 1 KOS1 MSAAN Andoni Ohangwena Multi-layered Aquifer KOH N/A Andoni, Olukonda (undifferentiated) Aquifer 1 (Andoni Fm) KOH1 MDAAN Andoni, Olukonda Aquifer 2 (Olukonda Fm) KOH2 VDAOL Olukonda Omusati Multi-zoned Aquifer (undifferentiated) KOM N/A Ombalantu, Beiseb, Olukonda, Andoni Karoo Sequence Aquifer/Aquitard Dwyka , Omingonde, Prince Albert, Kalkrand, KR KSA Karoo Ecca (undifferentiated) Etjo Owambo, Kombat, Tschudi, Huettenberg, Mulden-, Otavi-, Damara Sequence Aquifer (undifferentiated) D N/A Elandshoek, Maieberg, Ghaub, Auros, Gauss, Nosib- Berg Aukas, Varianto, Nabis Mulden Group Aquifer/Aquitard DM MGA Mulden Owambo, Kombat, Tschudi (undifferentiated) Huettenberg, Elandshoek, Maieberg, Ghaub, Auros, Otavi Dolomite Aquifer (undifferentiated) DO ODA Otavi Gauss, Berg Aukas, Varianto, Nabis DOT ODA Tsumeb Subgroup DOT1 ODA Damara Huettenberg Otavi DOT2 ODA Elandshoek (Tsumeb Subgroup) DOT3 ODA Maieberg Otavi Dolomite Aquifer DOT4 ODA Ghaub DOA ODA Abenab Subgroup DOA1 ODA Otavi Auros DOA2 ODA (Abenab Subgroup) Gauss DOA3 ODA Berg Aukas Nosib Group Aquifer/Aquitard (undifferentiated) DN N/A Nosib Varianto, Nabis Pre-Damara Basement (undifferentiated) B B Basement
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4.4.3 Aquifer Characteristics
Under the CRRWSDP, information was collected from the GROWAS database and from the hydrocensus undertaken for the DWA / BGR Project in 2007-2008. Only the most reliable borehole data was used. The hydrocensus showed that there were a number of boreholes included in the borehole registers that actually did not exist anymore, were abandoned or were found destroyed. Information on newly drilled boreholes (2009 in the Ohangwena Region) was also added to the database created under the CRRWSDP study.
The distribution of boreholes in the Cuvelai area is not uniform. The Oshana Region, i.e. the central portion of the CEB lacks boreholes, such that the interpolated maps created on GIS cannot provide reliable relevant information in that area. The reason for the low concentration of boreholes in the Oshana Region is the poor quality of the groundwater (not even suitable for livestock), which resulted in the development of the extensive pipeline supply network. Nevertheless, a number of hand dug wells were found in this area, but were not considered in the analyses conducted under the CRRWSDP study. The information about water quality in the Oshana Region was found to be less reliable than for the other parts of the CEB, but was still regarded as being partly predictable according to the aquifer types and the knowledge of the hydrogeologists working on this study and their experience with the groundwater in this area.
There is considerable variation within each aquifer system, some of which is due to the presence of separate aquifers at different depths in the same area. Thus, one borehole may pass through quite different layers of water in a multi-level system. The chemical qualities of the layers are also often quite different, some being brackish and others fresh, for example (Mendelsohn et al., 2013).
The various aquifers are discussed individually in the sections which follow.
4.4.3.1 The Multi-layered Ohangwena Aquifer (KOH) In the north-eastern region of the Cuvelai Area (refer to Figure 4.19), i.e. in the northern Oshikoto Region and in the central and eastern parts of the Ohangwena Region, boreholes were drilled in the multi-layered Ohangwena Aquifer (KOH). Most of the boreholes are situated in the KOH1, or Ohangwena I Aquifer of the Andoni Formation (approx. 140 to 200 m b.g.l.), which represents the main freshwater source of the Niipele Sub-Basin. The deepest boreholes reach the KOH2 or Ohangwena II Aquifer (intersected at a depth between 250 m and 350 m bgl), hosted in the Olukanda Formation, where red sandstones and clays are found. In the Eenhana area, the KOH2 contains fresh water under a layer of brackish water in the KOH1 aquifer.
This KOH aquifer is part of the Kalahari Sequence. The Kalahari aquifers are subdivided into five major units and named after the region or locality where they occur or where they were first described.
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4.4.3.1.1 The KOH1 or Ohangwena I Aquifer The KOH1 aquifer comprises green-beige semi-consolidated sandstone. It is considered to contain more than 10 billion m3 of potable groundwater (estimation from BIWAC 2006). Yields are between 2 and 15 m3/h in general and transmissivity values between 30 and 760 m2/d have been reported. In the map compiled for all the installed boreholes under the CRRWSDP study, yields seem to exceed 15 m3/h only very locally. The water levels are mostly deeper than 50 m and even deeper than 80 m toward the east. In the Eenhana area, west of the Eenhana- Okankolo line, the KOS aquifer overlies the KOH, but the depth of the boreholes indicate that they were drilled into the KOH1 or KOH2 aquifer.
The KOH1 is recharged by lateral through-flow from a proposed unconfined Kalahari aquifer in southern Angola. Isotope values of groundwater samples, which were taken in the northern Ohangwena Region close to the border with Angola, showed a relatively young conventional 14C age, thus demonstrating the proximity of the recharge area. Groundwater then flows southwards towards the Etosha Pan.
According to the main ions parameters, the groundwater in the eastern Ohangwena Region is mostly of good quality (Group A). However, there is also a gradient with the water quality deteriorating toward the south and the west, especially the fluoride content at the aquifer’s transitions, which are frequently above the threshold, and which makes these waters unsuitable for human as well as livestock consumption.
4.4.3.1.2 The KOH2 or Ohangwena II Aquifer According to Bittner (2006), the KOH2 aquifer, during recent investigations referred to as the Ohangwena II Aquifer, intersected between 130 and 380 m depth, is a fresh water aquifer (the BGR study (2013) suggests the KOH2 depth to be between 250 m and 350 m).
The identification of the freshwater aquifer(s) followed several steps. In 2007 to 2008, a groundwater hydro-census was conducted as a baseline study. Transient Electro-Magnetic (TEM) field surveys revealed potential freshwater horizons in the Ohangwena and Omusati Regions. Drilling campaigns between 2009 and 2010 verified a deep aquifer in the western part of the Ohangwena Region.
Additional observation boreholes were drilled 2011 in the Ohangwena Region to delineate the freshwater extent and to set-up a groundwater monitoring network. The geological setting of the Ohangwena I and II Aquifers was translated into a conceptual hydrogeological model. Extensive drilling campaigns, hydraulic tests, recharge calculations, water level and water quality monitoring provide information to parameterise the conceptual model and to develop a numerical groundwater model (this is still in progress).
Preliminary results reveal a huge potential of the Ohangwena II Aquifer (KOH2) for regional water supply. In cooperation with NamWater and the EU funded Integrated Water Resources Management Project, a pilot scheme for water supply tapping the KOH2 water resource is currently being developed.
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Some boreholes drilled southwest of Eenhana were sampled at different depths in the KOH2 aquifer. As a result, boreholes WW201045, WW201046 and WW201047 have a fluoride content of 3.4 mg/ℓ or less between 260 and 280 m depth. Between 330 and 340 m depth, however, WW201045 and WW201047 have fluoride concentrations of 6.1 and 4.4 mg/ℓ respectively. Fluoride concentrations in excess of 3 mg/ℓ classify the water as unsuitable for human consumption according to NamWater’s guidelines, whilst the NWQS require fluoride concentrations lower than 1.5 mg/ℓ, with the note that generally high ambient temperatures in Namibia may require a maximum value of 1 mg/ℓ. The high fluoride content is associated with high sodium values due to ion exchange processes. Total Dissolved Solids (TDS) are higher in the deeper layer as well, but stay within the band for Group A water quality. The KOH2 aquifer is thus not uniform.
Figure 4.20: Schematic Layout of the Ohangwena Aquifers (after BGR, 2013)
Geohydrological investigations of the Ohangwena II Aquifer are ongoing, and although reserve estimations for this significant fresh groundwater resource have been made, these estimations are only preliminary. Estimations are based on geohydrological data obtained from only a few exploration boreholes, while certain assumptions are made regarding the aquifer dimensions and storage capacity in the yet-unexplored parts of the aquifer. During an April 2013 information meeting in Eenhana, it was stated that one of the expected results of the investigation is defining the boundaries of the different groundwater bodies in the Cuvelai-Etosha Basin.
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Stored reserve calculations for the KOH2 aquifer were made using the following aquifer dimensions and storativity:
Stored reserve = 50 km x 50 km x 20 m x 0.1 = 5 x 109 m3 (5 billion m3)
It is important to note that the stored reserve does not necessarily equal the abstractable reserve. Although recharge to the KOH2 takes place (the recharge area is located in southern Angola), it is not yet quantified and the groundwater resource’s sustainability therefore still needs to be determined. Exploration of the aquifer is still ongoing, and as a result abstraction plans and recommendations must also still be developed. Based on the groundwater model to be developed, water availability will be determined and climate change scenarios and water abstraction schemes can be evaluated.
Due to the aquifer’s depth and the presence of overlaying confining layers, this aquifer is considered not vulnerable to pollution. It is known from deep boreholes drilled in the area that the water quality deteriorates southwards, becoming very saline towards Ondangwa. Salt water intrusion may therefore become a threat if future groundwater abstraction is not managed and coordinated properly. It is envisaged that a numerical groundwater model will be constructed to assist in the management of this aquifer. An abstraction threshold beyond which salt water intrusion become a reality can be established from such a numerical model.
4.4.3.2 The Oshivelo Multi-layered Aquifer (KOV) In the south-eastern CEB, north of Oshivelo and towards the east, some of the boreholes are found to exploit the Oshivelo Multi-layered Aquifer (KOV) aquifer, which is also part of the Kalahari Sequence. The investigation in this area was restricted, as most of the land is used by commercial farms, where the number of private boreholes is very high.
The KOV aquifer was first intersected at Oshivelo from where it extends in a north-westerly and easterly direction towards Tsintsabis and the Kavango Region border. Parts of the aquifer (KOV2) are confined, covered by brown-green clay, calcrete and clayey sand. At Oshivelo and towards the Etosha Pan, (at elevations lower than 1,100 m amsl) the aquifer is artesian, with free flowing water yielding up to 200 m3/h.
The aquifer material comprises mainly gravel and sand but also karstified calcrete / dolocrete. Transmissivity values between 100 and 10,000 m2/day are reported. The yields decrease towards the northwest where the aquifer is less permeable. The aquifer was the subject of a number of groundwater investigations and most recently studied by the BGR / DWAF as part of a larger project investigating groundwater occurrences in north-eastern Namibia.
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It is assumed that recharge to the KOV2 is to a high percentage via through-flow from the KEL and to a lesser extent from the underlying DOT. A groundwater isotope investigation by the DWAF in cooperation with the International Atomic Energy Association (IAEA) resulted in the interpretation that the signature of the KOV2 could be a product of mixing of water originating from both the KEL and the DO. Preliminary calculations of the potential groundwater through- flow from the KEL to the freshwater portion of the KOV2 resulted in a value of 8 Mm3/a and a safe yield of 4 Mm3/a. The 2005 groundwater study from Margane et al. in the Oshivelo area comes to the same conclusion. The groundwater quality and yields are good.
4.4.3.3 The Oshana Unconfined Aquifer (KOS) Underneath the central part of the CEB (refer to Figure 4.19), from about Eenhana in the northeast to Ruacana in the northwest and south towards the northernmost boundary of the Etosha National Park, the unconfined KOS aquifer is present as an alluvial deposit from the Andoni Formation, which is also part of the Kalahari Sequence. This aquifer is relatively shallow (from 6 to 80 m b.g.l.) and comprises sand and sandstone layers from a lacustrine and deltaic environment and have a good storage capacity. However, with seasonal and constantly shifting depositional environments, the resulting cross-bedding of sandstones and clay layers limits the hydrogeological properties. Clays have a lower specific yield than sandstones and sandy layers. Clay layers can therefore act as aquitards (beds of low permeability adjacent to an aquifer) and can hamper the relatively easy flow of groundwater into the basin. The few water levels reported have depths of less than 30 m bgl. The deeper ones in the east are more probably related to the KOH2 aquifer, as previously mentioned.
The KOS1 is recharged mainly by regular flooding of the iishana drainage system, by the so- called efundjas (floods) originating in Angola (refer to Figure 4.16). The water level gradient is very flat, and the groundwater flow in the Oshana Region is generally towards the Etosha Pan. The aquifer is tapped by a series of hand-dug wells, which supplied the bulk of the water used by the population in the Iishana Sub-Basin during the dry season prior to the construction of the pipeline network from the Kunene River. The KOS occurs in most of the Iishana Sub-Basin, the western and north-western parts of the Niipele and Tsumeb sub-basins respectively and the eastern part of the Olushandja Sub-Basin. The water quality and recharge is highly dependent on precipitation in, and runoff from, Angola.
The water quality varies from brackish to saline with very localised freshwater lenses in the oshana channels. A very small number of boreholes were drilled into the KOS and high yields are very locally reported. For the interpolation calculation on the maps produced for the CRRWSDP study, the information for the central region remains unreliable because of the very small number of boreholes, thus very low borehole density, and irregular and “distorted” borehole distribution. However, from the existing boreholes and according to experience gained in the area as far as the hydrogeological and hydrological system is concerned, it was concluded that the groundwater is not suitable for human and livestock consumption. There is however a fringe between the KOS and KOH, which could possibly be used for livestock consumption.
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4.4.3.4 The Omusati Multi-zoned Aquifer (KOM) In the Omusati Multi-zoned Aquifer (KOM), borehole numbers are higher than in the KOS aquifer, but according to the hydrocensus, borehole maintenance is problematic. The KOM aquifer is situated to the south-west of the KOS aquifer and comprises unconsolidated to semi- consolidated sediments of the Kalahari Sequence, mainly sand, clay and calcrete / dolocrete, but also large evaporitic deposits. The aquifer is separated and distinguished from the KOS because it is not recharged by the Cuvelai drainage system. Recharge rather takes place by means of lateral through-flow from the KEL and DO aquifers located to the west.
The water levels in the KOM aquifer are very shallow. The salinity of the subsurface sediments is high, causing the deterioration of groundwater quality towards the basin centre. The change in water quality can be very sudden, with freshwater boreholes in the KEL being only a few kilometres away from boreholes with saline groundwater in the KOM. The change in salinity is believed to be caused by the ancient proto-Etosha Lake, which covered most of today’s central CEB. Thick evaporitic deposits of the playa-lake remained after rapid evaporation of seasonal water inflow from northern directions. The salts have been dissolved by rainwater, resulting in the brine lake conditions throughout the central CEB. Large gypsum deposits still exist as proof of the existence of the proto-Etosha Lake. The gypsum is responsible for the high sulphate concentration in the groundwater of the KOM (mainly Group D waters). Fluoride, TDS, nitrate, chloride, magnesium and calcium levels are often found to be very high, resulting in groundwater being unsuitable for human or livestock consumption (refer to the following figures). This is probably the main reason why the south-eastern part of the Omusati Region is scarcely populated. Only scattered cattle posts exist, where the herders have to be supplied with trucked-in drinking water from the north. With the shallow water levels, cattle herding is a problem, generating high nitrates levels around some boreholes, causing additional, anthropogenic elevation in nitrate concentrations in these shallow groundwaters.
This area is considered one of the main investigation areas of the groundwater investigations in the CEB. Recently, two small-scale, pilot desalination plants were built in Amarika and Akutsima which desalinate the groundwater from nearby boreholes for consumption by the local community using different desalination methods. Considering the groundwater quality across the Cuvelai area, groundwater desalination can be more feasible than piped water to supply potable water to remote and isolated communities.
4.4.3.5 The Etosha Limestone aquifer (KEL) In the western part of the Cuvelai area, the Etosha Limestone Aquifer (KEL) is present with a thickness of up to 100 m locally. It also underlies the southern part of the Etosha National Park, which is not part of this investigation. It is believed to be a groundwater calcrete of sedimentary- evaporitic genesis. The KEL constitutes an economically important aquifer because of its easy accessibility (shallow water table) and often good yields and water quality. High yields are reported from the area southeast of Oshivelo, along the Omuramba Owambo, south of Halali in the Etosha National Park (all outside the Study area) and locally in the western Olushandja Sub-Basin.
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The aquifer is partly recharged by lateral through-flow from the DO aquifers of the basin margin, but isotope studies showed that local recharge to the KEL contributes by more than 70% to the north-westerly groundwater flow. The groundwater vulnerability is relatively high and elevated nitrate concentrations are often measured particularly when the borehole is located near a livestock post. In the south-western Omusati and in the Kunene Region, the water levels are usually less than 50 m bgl. Some high sulphate, chloride, calcium, nitrate and magnesium levels are found, exceeding the limits for Group D water. However toward the west, the quality seems to improve.
4.4.3.6 The Otavi Dolomite aquifer (DO) The last aquifer represented in the Cuvelai area is the Otavi Dolomite Aquifer (DO) from the Damara Sequence, which partly underlies the KEL aquifer. The DO aquifer is situated south of Ruacana, but it is also found south of the KEL formation in the south of the Etosha National Park, as an outer rim of the CEB.
The carbonates of the DO constitute a thick fractured and partly karstified aquifer system representing the main hard rock aquifer of the southern and western CEB. From top down, the Otavi Dolomite Aquifer is composed of the fractured to karstified dolomite aquifers of the Hüttenberg (DOT1), Elandshoek (DOT2) and upper Maieberg (DOT3) formations (Tsumeb Subgroup). The lower Maieberg as well as the Chuos formations, which separate the upper Tsumeb Subgroup from the lower Abenab Subgroup, act as aquitards.
The dolomites of the Elandshoek and Hüttenberg formations have the highest average transmissivity values of 300 and 1,700 m2/day respectively and are therefore the most important fresh water aquifers in the outer rim of the CEB. The fractured dolomites of the Auros, Gauss and Berg Aukas formations (DOA) represent the major lower dolomite aquifer with transmissivity values ranging from 10 to 1,000 m2/day. The main outcrop areas of the DOA in the CEB are in the Abenab Area and northeast of Otjovazandu in the Etosha National Park.
The groundwater flow is directed towards the centre of the CEB, the Etosha Pan. Subsequently groundwater recharged in the fractured dolomites of the Otavi Mountain Land (DO) also flows north- and eastwards, feeding the overlying unconfined and confined Kalahari aquifers (KEL+KOV1 and KOV2) via faults, fractures and other preferential flow paths such as along bedding planes.
The mostly fine-grained meta-sediments of the Mulden Group (shale, quartzite) as well as the Nossib Group rocks are generally regarded as aquitards (DM). Locally, however, with transmissivity values of 300 m2/day, and when confined under Kalahari Sequence sediments, e.g. in western Omusati or near Okaukuejo (Etosha National Park), they could contain abstractable volumes of mostly fresh groundwater.
The salinity is generally low, and, except for a few exceptions in some magnesium or nitrate contents, the quality is good and the yields are acceptable.
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4.4.3.7 The Karoo Sequence Although not out-cropping, the Karoo Sequence plays an important role in the geohydrological environment in the CEB. The influence of this sequence is however more important to the hydrogeology outside of the Cuvelai area. In the central CEB the Karoo rock succession is made up of glaciogenic rocks (largely tillite interbedded with shale) of the Dwyka Formation, shales and coals of the Prince Albert Formation, and aeolian sandstone of the Etjo Formation (at Nanzi and recently reported from Oshivelo). Aeromagnetic surveys indicate basaltic lavas equivalent to the Rundu Formation in the south-east of the basin beneath the Kalahari succession. Recent deep drilling between Tsumeb and Oshivelo as part of the Tsumeb Groundwater Study proved that impermeable Karoo sediments such as shale and mudstone as well as basalt are “sandwiched” between the upper Kalahari sediments and the lower Otavi dolomites. The Karoo Sequence aquitard (KR) comprises rocks like shale, mudstone, sandstone and basalt. It is mainly described as an aquitard (transmissivity values between 1 and 10 m2/day), but can locally yield abstractable volumes of groundwater, often when confined under Kalahari sediments.
The Karoo aquitard hydraulically separates the underlying Otavi Dolomite aquifers from the overlying Kalahari aquifers, except where dolomite mountains crop out at or near surface, e.g. at Halali, or south of Oshivelo, due to rough pre-Kalahari and pre-Karoo topography. In these hydrogeological window areas, hydraulic contact and continuity between Otavi Dolomite aquifers and the Kalahari aquifers is possible, allowing recharge by lateral through-flow from the rim towards the centre of the basin.
Only the aeolian Etjo Formation sandstone (also forming the Waterberg Plateau east of Otjiwarongo) can be considered an aquifer. Its presence in the Oshivelo area was already reported during earlier drilling campaigns but it was intersected again in two exploration boreholes WW40935 and WW40967 at depths greater than 200 m. The transmissivity of this aquifer unit was determined as 82 and 300 m2/day from these boreholes respectively. The regional extent of the Etjo sandstone is however not known and is most probably limited.
4.4.4 Groundwater Sub-Basins
The potential of groundwater as a water supply resource for water consumption in the Cuvelai area depends on the overall groundwater quantity and quality (Figure 2.15), the extent of the pipeline network (Figure 1.3) and the water demands, and differs throughout the Cuvelai area. The location of the Olushandja Sub-Basin to the west, the Iishana Sub-Basin in the central portion and the Nipele Sub-Basin to the west of the Cuvelai area, in conjunction with the extent of the pipeline network and the ground level elevations, is shown in Figure 4.21.
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Figure 4.21: Groundwater Sub-Basins, Existing Water Supply Infrastructure and Elevations (LCE, 2011)
4.4.4.1 Borehole Depths and Yields The depths of the boreholes in the Cuvelai area are shown in Figure 4.22, the water levels in these boreholes in Figure 4.23 and the yields of these boreholes in Figure 4.24.
Figure 4.22: Borehole Depths in the Cuvelai Area (m)
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The variability in borehole depth, particularly in the western portion of the Cuvelai area is evident, whilst borehole depths are more homogenous in the eastern portion of the area.
Figure 4.23: Water Levels in the Cuvelai Area Boreholes (m bgl)
The variability of the water table in the western portion of the Cuvelai area explains the variability in borehole depths in this area. Water levels can be seen to progressively become deeper towards the eastern parts of the Cuvelai area.
Figure 4.24: Yields of the Boreholes in the Cuvelai Area (m3/h)
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Borehole yields can be seen to be low in the central portion of the Cuvelai area, and high in the south, where artesian water is found in the Oshivelo Multi-layered Aquifer. Reasonable yields of between 6 and 15 m3/h are encountered across most of the Cuvelai area.
4.4.5 Water Quality
With regard to water quality, reference is made to the “Guidelines for the Evaluation of Drinking- Water for Human Consumption with Regard to Chemical, Physical and Bacteriological Quality” document (NamWater, 1998), according to which NamWater classifies water as follows:
1. Group A: Water with an excellent quality, 2. Group B: Water with good quality, 3. Group C: Water with low health risk, 4. Group D: Water with a higher health risk, or water unsuitable for human consumption.
Reference is also made to the Namibian Water Quality Standards (NWQS) which, once implemented, will provide the minimum standard to which portable water should adhere, whilst the Namibian Water Quality Guidelines (NWQG) provide an “ideal guideline” for potable water quality. In some instances, reference is also made to water quality guidelines advocated by and documentation from the World Health Organisation (WHO) as well as to those of the Environmental Protection Agency (EPA) of the United States.
4.4.5.1 Total Dissolved Solids Total Dissolved Salts (TDS) is the term used to describe the inorganic salts and small amounts of organic matter present in solution in water. The principle constituents are usually calcium, magnesium, sodium and potassium cations (positively charged) and carbonate, hydrogencarbonate, chloride, sulphate and nitrate anions (negatively charged) (WHO, 2011b). The distribution of some of these individual constituents (calcium, magnesium, chloride, sulphate and nitrate) are provided in the proceeding sections. The concentration of TDS in water is most commonly determined by measuring the specific conductivity of water with a conductivity probe (WHO, 2011b). TDS values have not been linked directly to adverse health effects, and therefore guideline values are not readily available; guidelines are instead available for some of the constituent compounds (see below) (after WHO, 2011).
However, high concentrations of TDS may result in the water being objectionable to consumers on the basis of taste, and could lead to the excessive scaling of pipes, water meters and household appliances (above 500 mg/ℓ). Water with concentrations of TDS below 1,000 mg/ℓ is usually acceptable to consumers, although “good” water, taste-wise, is regarded as having TDS values less than 600 mg/ℓ (after WHO, 2011b). If a threshold of 2,000 mg/ℓ is used, as per the NQWS, it can be seen (refer to Figure 4.25), that groundwater to the west and east of the central Cuvelai area is of acceptable quality, whilst that in the central portion is not (allowing for exceptions in the central western and central eastern areas).
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Figure 4.25: Total Dissolved Solids Concentrations in the Cuvelai Groundwater (mg/ℓ)
The very high TDS values, in excess of 6,000 mg/ℓ across the majority of the central Cuvelai area, are the reason why the pipeline supply network was developed in this area. A TDS value of 5,000 mg/ℓ is considered the minimum threshold beyond which water is classified as “brine”.
4.4.5.2 Concentrations of Calcium The concentrations of calcium in the groundwater in the Cuvelai area is shown in Figure 4.26. Concentrations of calcium of greater than 400 mg/ℓ would result in water being classified as unsuitable for human consumption (according to NamWater’s guidelines), which can be seen to be the case in the groundwater water in the south-central part of the Omusati Region.
Figure 4.26: Calcium Concentrations in the Cuvelai Groundwater (Ca in mg/ℓ)
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Concentrations of calcium of greater than 150 mg/ℓ, which are not permissible according to the NWQS, are located across a larger area in the south-central part of the Omusati Region as well as in the area around Outapi.
4.4.5.3 Concentrations of Magnesium The concentrations of magnesium in the groundwater in the Cuvelai area is shown in Figure 4.27.
Figure 4.27: Magnesium Concentrations in the Cuvelai Groundwater (Mg in mg/ℓ)
Concentrations of magnesium (as Mg) of 200 mg/ℓ and higher, which would classify the water as unsuitable for human consumption (according to NamWater’s guidelines), are found in the western part of the Cuvelai area, in the central part of the Omusati Region, south of Ruacana. Concentrations of magnesium (as Mg) of greater than 70 mg/ℓ, which are not permissible according to the NWQS, are located across a large swathe of the western Cuvelai area.
With the exception of isolated cases in the east, elsewhere in the Cuvelai area, magnesium concentrations are acceptable.
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4.4.5.4 Concentrations of Chloride The concentrations of chloride in the groundwater in the Cuvelai area is shown in Figure 4.28.
Figure 4.28: Chloride Concentrations in the Cuvelai Groundwater (Cl in mg/ℓ)
Chloride concentrations greater than 250 mg/ℓ, which is the limit for Group A water (NamWater’s guidelines), can give rise to detectable taste in water. However, chloride concentrations of greater than 1,200 mg/ℓ, which would classify the water as unsuitable for human consumption (according to NamWater’s guidelines), can be seen to occur in the majority of the central portion of the Cuvelai area. Concentrations of Chloride of greater than 300 mg/ℓ, which are not permissible according to the NWQS, are located across the majority of the Iishana Sub-Basin, parts of the Olushandja Sub-Basin and in a west – east band across the southern part of the Nipele Sub-Basin.
Chloride concentrations in the extreme western and north-eastern areas are acceptable.
4.4.5.5 Concentrations of Fluoride The concentrations of Fluoride in the groundwater in the Cuvelai area is shown in Figure 4.29.
Fluoride concentrations above 3 mg/ℓ may cause abnormal development of the skeleton on children, and can also cause the mottling and wearing away of teeth in both humans and livestock (Mendelsohn et al., 2013) and classifies the water as unsuitable for human consumption (according to NamWater’s guidelines). Exposure to excessive fluoride consumption over a lifetime may lead to an increased likelihood of bone fractures in adults and may result in effects on bone leading to pain and tenderness (EPA, 2009 & EPA website).
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The NWQS require fluoride concentrations lower than 1.5 mg/ℓ, with the note that generally high ambient temperatures in Namibia may require a maximum value of 1 mg/ℓ.
Water with levels of fluoride of above 1.5 mg/ℓ can be seen to occur over the whole Cuvelai area. Concentrations of fluoride greater than 3 mg/ℓ occur over a large portion of the central Cuvelai area, and in a belt extending to the east, north of Oshivelo. The distribution of higher concentrations of fluoride is similar to that of high concentrations of chloride (Figure 4.28).
Figure 4.29: Fluoride Concentrations in the Cuvelai Groundwater (F in mg/ℓ)
4.4.5.6 Concentrations of Nitrates The concentrations of nitrates in the groundwater in the Cuvelai area is shown in Figure 4.30.
Concentrations of nitrates (as N) of 40 mg/ℓ and higher, which would classify the water as unsuitable for human consumption (according to NamWater’s guidelines), are found in the central and southern parts of the Omusati Region in the west of the Cuvelai area. The NWQS require nitrate concentrations (as N) lower than 11 mg/ℓ. High concentrations of nitrates are found around Ruacana, in the central Omusati Region (very high concentrations), in isolated patches in the Ohangwena Region and north of the Etosha National Park to the west of Omuthiya. This latter area is frequently used as a grazing area for livestock, where cattle dung may contribute to elevated levels of nitrates.
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Figure 4.30: Nitrate Concentrations in the Cuvelai Groundwater (N in mg/ℓ)
Whilst healthy adults appear able to consume fairly large amounts of nitrates without adverse health effects, prolonged intake of high levels of nitrates are linked to gastric problems (CSU, 2010). Once taken up in the body, nitrates are converted to nitrites. Nitrite is absorbed into the blood and haemoglobin, the oxygen-carrying component of blood, is converted to methemoglobin, which does not carry oxygen efficiently. This results in reduced oxygen supply to vital tissues, particularly the brain. Pregnant women, adults with reduced stomach acidity and people deficient in the enzyme that changes methemoglobin back to normal haemoglobin are all susceptible to nitrite-induced methemoglobinemia. This condition, also known as blue baby syndrome, is also potentially lethal to infants younger than six months, as the stomach acid in young infants in not as strong as in older children and adults. This causes an increase in the bacteria which convert nitrate to nitrite, leading to methemoglobinemia (after CSU, 2010 and EPA website). Based on a body weight of 5 kg for infants, a guideline value of 3 mg/ℓ for the concentration of nitrates can be derived (WHO, 2011a).
4.4.5.7 Concentrations of Sulphates The concentrations of sulphates in the groundwater in the Cuvelai area is shown in Figure 4.31.
The limit of Sulphate concentration (as S03) for Group A water is 200 mg/ℓ. The threshold for aesthetic effects (taste and odour) is 250 mg/ℓ, beyond which sulphate produces a noticeable taste. Sulphates may also contribute to the corrosion of distribution systems. At concentrations greater than 1,200 mg/ℓ, beyond which the water is regarded as unsuitable for human consumption (NamWater, 1998), sulphates have a laxative effect (after WHO, 2009 and EPA website). The NWQS require sulphate concentrations lower than 300 mg/ℓ.
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Figure 4.31: Sulphates Concentrations in the Cuvelai Groundwater (SO4 in mg/ℓ)
Water with concentrations of Sulphates above 300 mg/ℓ can be seen to occur over a large portion of the central Cuvelai area, and in a belt extending to the west into the central part of the Omusati Region and south eastwards towards Oshivelo.
4.4.6 Groundwater Supply Potential
4.4.6.1 The Niipele Sub-Basin Most of the villages and settlements are supplied by groundwater sources as well as from seasonally water filled pans that are spread over the area. Since independence, a large number of water wells were successfully drilled into the Ohangwena Multi-layered Aquifer (KOH) to supply the scattered villages and to guarantee most of the population access to safe drinking water. At the end of 2008, about 30 new boreholes were successfully drilled from Oshikunde towards the east and 14 were drilled in 2009 on resettlement farms. The water quality in this area is in general very good. The main settlements, i.e. Okongo, Omundaungilo and Ohumbulwa are supplied with groundwater from their own boreholes, operated by the DWSSC, the Ministry of Health and other Government institutions. The water is used for livestock farming and no irrigation takes place. There are, however, gardening projects planned in the sub-basin.
The south-western part of the sub-basin borders to the brine lake area and towns, villages and settlements such as Eenhana, Epembe, Okankolo and Onuulaye are connected to the pipeline network supplying freshwater from the Kunene River. In the transition zone between the two areas, the people are supplied with substandard groundwater from boreholes. Exploration boreholes have shown that a deeper fresh water aquifer exists. If not fresh, this water can sometimes be used at least for livestock supply. The deeper KOH2 is probably safer than the KOH1, however, care must be taken with fluoride contents.
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4.4.6.2 The Iishana Sub-Basin A network of canals and pipelines supply the people in the Iishana Sub-Basin with water originating from the Kunene River in Angola. Water purification plants in this sub-basin are located at Outapi, Ogongo and Oshakati. Most of the water is distributed to storage tanks at schools and clinics, to government buildings and businesses in the major towns and to community water points spaced along the pipelines in the rural areas. There is almost no existing borehole in this central part of the Cuvelai area. The salinity, originating from the shallow water levels and evaporation processes, is the main detractor for using groundwater as a safe supply. In addition, the groundwater quality system is highly dependent on the annual recharge conditions, which makes it very vulnerable to small time-scale changes. Groundwater should not be used as a source for drinking water supply in this area. Chemical parameters generally also exceed the threshold for livestock drinking water.
4.4.6.3 Olushandja Sub-basin Until about 2008, water was transported from the Olushandja Dam via the unlined Etaka Canal to the areas around Tsandi and Okahao primarily for livestock watering. This canal is however no longer in regular use. Within the Olushandja Sub-Basin, two purification plants are located at Olushandja and Outapi.
Two pilot desalination plants were recently installed in Amarika and Akutsima in 2010, providing about 5 m3/d of potable water to the rural communities.
The western part of the sub-basin is supplied mainly from groundwater resources. The dolomite aquifer (DO) and the calcrete platform of the foreland (KEL) comprise groundwater of good quality and quantity. Towards the basin centre, the water quality deteriorates and near the Etaka Canal, all groundwater is saline. The main settlements Outapi, Ruacana, Onesi, Tsandi and Okahao are served with Kunene water via the pipeline network. The Etunda irrigation project between Ruacana and Olushandja is one of the largest single water consumers in Namibia. Large areas within the sub-basin are not populated, due to the absence of surface and fresh groundwater resources. Deeper groundwater resources underlying the saline Kalahari sediments have not yet been completely explored.
The water quality is highly variable in the overall sub basin. In the north-western area, around Ruacana, the water quality is good and, in the middle-western area, sulphate, magnesium and calcium concentrations are sometimes problematic. Locally, nitrate and fluoride concentrations are also above acceptable consumption thresholds.
4.4.7 Summary of the Potential of Groundwater in the Cuvelai Etosha Basin
According to the investigation and maps produced for the CRRWSDP study, the potential of groundwater is not homogeneous and depends on regional variations, which themselves depend on local climatic conditions, recharge and aquifer types. The general idea is that the outer recharge areas (to the west and east of the Cuvelai area) offer safer water supply, and that towards the interior of the basin, quality decreases and other water supply options must be used (pipelines, desalination plants, etc.).
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The Iishana Sub-Basin which forms the central part of the Cuvelai area does not offer a safe groundwater supply potential, as the entire area is subject to very high evaporation rates, which results in the increase of the salinity of the groundwater. In addition, the groundwater is highly dependent on Angolan climatic conditions. Even if local fresh water lenses can be found, the variability in the lithology does not permit the accurate siting of boreholes which would produce good quality water. Most of the few boreholes that have been drilled in the past are no longer in use.
In the Niipele Sub-Basin on the other hand, groundwater can be regarded as an important and sustainable water resource to supply water to rural communities. The KOH aquifer provides relatively safe water at an acceptable quality for human consumption. Yields generally do not exceed 15 m3/h. Nonetheless, in the transition between this sub-basin and the Iishana Sub- Basin, as well as in the southern part of it, care has to be taken due to the increasing fluoride contents.
Towards the KOS aquifer (refer to Figure 4.19), the drilling depth has to be increased to ensure that the deeper KOH2 aquifer is reached, and care must be taken to avoid contamination from the upper aquifers to the lower ones, as well as contamination from lower aquifers to the upper ones.
The Olushandja Sub-Basin is more variable in terms of the potential of using the groundwater for rural water supply. The maps shown indicate that the groundwater quality is unsuitable for human consumption in the boreholes drilled in the KOM aquifer in the south eastern Olushandja Sub-Basin. On the north western edge of the Etosha National Park, in the KEL aquifer, which is probably closely linked to the DO aquifer through recharge from it, relatively good quality water can be found. It is however important to note that due to the shallow water levels, this groundwater is highly vulnerable to contamination by livestock droppings, which is confirmed by the locally high nitrate concentrations (refer to Figure 4.30).
Toward the north the groundwater quality becomes more variable. The evaporitic genesis of the KEL aquifer is revealed by its high sulphate and magnesium contents.
To the south and southwest of Ruacana, groundwater quality from the DO aquifer is generally classified as Group A or B. The potential for water supply is thus considerable.
The Tsumeb Sub-Basin, mainly falling out of the boundaries of the Cuvelai area investigated for this Study, also offers important potential for groundwater supply. Highly exploited, the existing boreholes exhibit high yields and relatively safe water quality. Again, water quality deteriorates towards the north and towards the interior of the CEB.
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Table 4.5: Summary of the Groundwater Potential in the Cuvelai Area (Mendelsohn et al., 2013)
Depth Below Borehole Aquifer System Main Rock Type Surface Water Quality Yields (m) (m3/h) Ohangwena Multi-Layered Sand, sandstone 60 – 300 Fresh to brackish 1 – 50 Aquifer (KOH) Conglomerate, Oshivelo Multi-Layered sandstone, sand, 30 – 150 Fresh to brackish 5 – 100 Aquifer (KOV) dolocrete, calcrete Fresh, locally high Etosha Limestone Aquifer Dolocrete, calcrete, 10 – 100 nitrate 3 – 100 (KEL) sand concentrations Oshana Multi-Layered Sand, calcrete / Saline to hyper 10 – 80 1 – 30 Aquifer (KOS) limestone saline Omusati Multi-Zone Sand, clay and Brackish, freshwater 10 – 50 1 – 30 Aquifer calcrete, dolocrete in places Otavi Dolomite Aquifer Dolomite 20 – 250 Fresh More than 50
4.4.8 Current Utilisation of Groundwater Resources in the Cuvelai Area
Groundwater is primarily used for domestic water supply (both for rural settlements and in bulk to larger towns) and livestock watering. The groundwater utilisation of the entire Cuvelai Basin is discussed in the 2010 national Integrated Water Resources Management Plan, detailing the groundwater use by sector. Assessment of the groundwater use (2010) is shown in Table 4.6.
Table 4.6: Groundwater Utilisation in the Cuvelai-Etosha Basin (2010)
Water Use Category of Use (m3/a)
Domestic use (NamWater bulk supply) 589,736
Domestic use (DWWSSC rural supply) 6,507,594
Adjusted livestock 7,561,343
Total 14,658,673
The above summary excludes groundwater used in the greater Cuvelai Basin, as outside the boundaries of this Study Area, water is used for irrigation (12 Mm3/a) and by local authorities (5.6 Mm3/a).
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4.4.9 Recharge
The groundwater recharge mechanism of the Cuvelai Basin, which extends much further than the Niipele, Iishana and Olushandja Sub-Basins, is not yet entirely understood. The results of a stable isotope study in the north of the basin, together with numerical groundwater modelling in the south, suggest that the following scenarios are the most likely to occur:
Direct recharge from precipitation, which replenishes the unconfined Kalahari aquifers at a rate of 0.2% of the mean annual rainfall, and 0.25% across the calcrete areas of the Etosha Limestone Aquifer, Indirect recharge through oshanas originating from Angola is likely to be the major driving force of groundwater recharge of the deeper aquifers such as the KOH1 and KOH2 in the north, Leakage occurs from the dolomitic aquifers in the south into the Kalahari aquifers. Thus groundwater recharged in the fractured dolomites of the Otavi Mountain Land (DO) also flows north- and eastwards, feeding the overlying unconfined and confined Kalahari aquifers (KEL, KOV1 and KOV2) via faults, fractures and other preferential flow paths such as along bedding planes.
Figure 4.32 shows a block diagram of the perceived more complex recharge mechanism in the southern part of the Cuvelai Basin.
Figure 4.32: Block diagram showing recharge in the southern Cuvelai Basin (DWA, 2001)
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WATER SUPPLY INFRASTRUCTURE IN THE CUVELAI AREA
5.1 BASIC LAYOUT OF WATER SUPPLY INFRASTRUCTURE IN THE CUVELAI AREA 5.1.1 Introduction
The central portion of the Cuvelai area is served with raw and potable water via canals and pipelines respectively. In this central area, the canals, purification plants, reservoirs (both elevated and at ground level) pump stations and bulk transfer pipelines belong to and are operated by NamWater, whilst the secondary or distribution pipelines mostly belong to and are operated by the MAWF (DWSSC).
Areas to the west and east of the central pipeline network of the Cuvelai are supplied with groundwater via individual borehole installations. The water supply infrastructure in the Cuvelai is shown in Figure 5.1.
Figure 5.1: Layout of the Water Supply Infrastructure in the Cuvelai Area
The water supplied via the canals and pipeline network in the Cuvelai area is drawn from Calueque Dam, which is situated in Angola, some 30 km upstream of the Ruacana Falls and 15 km north of the Namibian – Angolan Border, under an abstraction agreement between the Namibian and Angolan Governments which dates back to 1969 (refer to Section 3.4.1.4).
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This water is pumped a short distance, after which it gravitates into Namibia via the Calueque – Oshakati Canal, after which some water is drawn off to supply the Etunda Irrigation Scheme. The remainder of the water gravitates past Olushandja Dam towards Oshakati via the canal, where it is purified for distribution to the north, south and east. Water drawn from the canal between Olushandja and Oshakati is also treated at Olushandja, Outapi (Ombalantu) and Ogongo prior to further distribution. Water is drawn from the canal into Olushandja Dam for emergency storage only.
5.1.2 Separation of Schemes and Water Supply Zones The canals and particularly the pipelines in the central Cuvelai area form an extensive and interconnected network which crosses constituency and regional boundaries. Several of the bulk transfer pipeline schemes are interlinked and can be supplied from more than one point. With the completion of the Cuvelai Bulk Water Master Plan, the bulk water supply infrastructure in the Cuvelai area was separated into eight water supply zones (LCE, 2009), in a way not dissimilar to that proposed in the 1991 Regional Master Water Plant (DWA, 1991). A schematic layout of the bulk water supply infrastructure (that belonging to NamWater) in the Cuvelai area is shown in Figure 5.2, which illustrates the interconnectedness and complexity of these schemes.
The separation of these water supply zones was done on the basis that the various purification plants would serve as points of supply for downstream schemes, and therefore represent logical starting points for the separation of schemes. Ondangwa, whilst not a purification plant, has a very large storage capacity, and can therefore also be regarded as a point of supply for downstream schemes. Six of these zones (Zones 2 to 7) correspond to the schemes supplied by the Olushandja, Outapi, Ogongo and Oshakati Purification Plants, where the Ogongo and Oshakati Purification Plants supply water to two zones each. The infrastructure south east of Ondangwa, is included in Zone 8. All but one of these water supply zones (Zone 8) commence at a purification plant. The Calueque Pump Station and the Calueque –Oshakati Canal are combined into Zone 1 (LCE, 2009). These eight water supply zones are shown in Figure 5.3.
The hydraulic capacity modelling conducted for the rural water supply schemes belonging the MAWF (DWSSC) under the CRRWSDP used the same 8 water supply zones from the Cuvelai Bulk Water Master Plan, subdividing these zones into 30 sub-service areas for the investigations into the various rural or distribution pipeline schemes (LCE, 2011).
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Figure 5.2: Schematic Layout of the Bulk Water Infrastructure in the Cuvelai Area (LCE, 2009)
SANTA CLARA
CALUEUQUE OSHIKANGO RWS RE ER RE ER TOWN PS PS
RUACANA HB RAW O BORDER D RE ER IB OSHALI O PS
OMUNGWE- ONGENGA OMAFO EENHANA LUME TOWN RWS TOWN RE ER TOWN RE ER RE ER RE ER TOWN PS PS PS 1(CANALS, CALUEQUE PUMP STATION AND OLUSHANDJA DAM) RWS OL-RU OLUSHANDJA OHANGWENA RUACANA BOOSTER OKALO O -NGO ND RE ER RE ER OTHER RWS RE ER OBE RWS PS PS PP PS 5 ELIM OMAKANGO E NDO OLUSHANDJA DAM RE ER TOWN RE ER TOWN ONAMBUTU TOWN RWS L A 7 PS PS
2 OLUSHANDJA OLUSHANDJA OSHAANGO S/W N/W DECOMISSIONED RWS TOWN OTHER TOWN RWS RE
PS PS
RWS OUTAPI OSHIKUKU ONGHA IINDANGUNGU OSHIGAMBO
RE ER RE ER RE ER RWS RE ER RE ER TOWN ETAKA CANAL PS PP PS PS PS PS RWS
OGONGO OSHITAYI E UNDA RWS RWS RWS RE ER TOWN RE ER PVT
3 PS PP PS
OSHAKATI ONGWEDIVA ONDANGWA ONANDJOKWE
ON RWS E RWS RWS TOWN RE ER RE ER TOWN RE ER TOWN RE ER TOWN S I PS PP PS PS PS OTHER
TSANDI OKAHAO O U N U IIKO- A N K KO RWS RE ER RE ER OTHER A G W TOWN TOWN TOWN N U A L D L - A A A PS PS
OSHALI ONAYENA
RWS RWS TOWN RWS RWS RWS TOWN RWS RE RE ER 4 6 PS PS 8
OKA- N K O LO
OKATOPE O LEGEND MA PAL RE ER1 RWS E PS RWS BULK CONSUMER
ONEMBENGE O MA ER2 ER3 PA NW SCHEME COMPONENT L E PS
OGONGO NW PUMP STATION RE GROUND LEVEL RESERVOIR OMU- N T RE ER E RWS RWS ER ELEVATED RESERVOIR LE
PS PP PS PUMP SET
PP PURIFICATION PLANT
PIPE WITH FLOW DIRECTION RWS
CANAL WITH FLOW DIRECTION
PRODUCTION WATER METER OMUTHIYA AMBE - NDE RE ER4 ER5 RWS BLANKED-OFF PIPELINE PS
ISOLATING VALVE
NON-RETURN VALVE RWS RWS
WATER SUPPLY ZONE
OMUTSE GWONIME ER7 6 ZONE NUMBER
Chapter 5: Water Supply Infrastructure in the Cuvelai Area 5-3 THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
Figure 5.3: Eight Water Supply Zones in the Cuvelai Area (LCE, 2009)
5.2 INFRASTRUCTURE AT CALUEQUE
5.2.1 Calueque Dam 5.2.1.1 Background and History Construction of Calueque Dam commenced in the early 1970s and was never completed, due to the outbreak of hostilities in Angola, followed by Angola’s independence from Portugal in 1975. The Contractor left the site in May 1976, after which a construction team of the then DWA took over, only to leave the site with only two to three months of work left, with only the northern embankment and the installation of 8 of the 10 sluice gates still to be completed. During an air attack on the South African Defence Force in 1988, some damage was caused to the main concrete section of the dam housing the pump station as well as the pipeline to Namibia (after DWA, 1991).
Chapter 5: Water Supply Infrastructure in the Cuvelai Area 5-4 THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
Calueque Dam, shown in Figure 5.4 below, was built to serve as an intermediate storage for the Ruacana hydro-power station located approximately 20 km further downstream on the Kunene River, and as an abstraction point for water supply to the Cuvelai area. The dam is located approximately 40 km upstream of the Ruacana Falls and 15 km north of the Namibian – Angolan Border (LCE, 2011).
Figure 5.4: Aerial View of Calueque Dam (LCE, 2011)
Calueque Village
Flow
Pipeline
N
Canal
5.2.1.2 Details of Calueque Dam Following the 1969 abstraction agreement for the transfer of water to Namibia, the first phase of the dam, consisting of a pump station to house two 3 m3/s pump sets, the Calueque Pipeline, the Calueque – Border and Border – Olushandja Canals, was completed in 1971. Construction of the second phase, comprising the dam itself and extensions to the pump station, commenced in March 1973 (LCE, 2011).
The dam consists of the following components: a southern earth embankment; a concrete central section comprising the existing pump station, a new pump station for three pump sets, an entrance hall and viewing gallery, a hoist room for the sour outlet gats, two scour outlets with radial gates, 10 spillway bays with radial gates and a northern embankment. The total length of the dam is approximately 2.3 km and the height of the wall at mid-river is 17 m (LCE, 1992c).
Chapter 5: Water Supply Infrastructure in the Cuvelai Area 5-5 THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
Instead of a capacity of 475 Mm3 at a water level of 1,098 m asl, being the originally intended Full Supply Level (FSL), the storage capacity is only about 10 Mm3 at a water level of 1,092 m (after LCE, 1992a, LCE, 1992c and NamWater, 2004).
With the exception of short periods in 1985 and 1988, between 1976 and 1990, no water was abstracted from Calueque Dam, and water was instead supplied to the Cuvelai area from Ruacana (after LCE, 1992c).
Figure 5.5: Calueque Dam
(l) Embankment viewed from downstream (r) Embankment viewed from the top. Upstream to the right
The concrete portion of the dam wall has a scour outlet with an inlet level of 1,088 m asl and a spillway at an elevation of 1,092 m. In the 1990s, stop logs were inserted in the scour outlet. These do not fully block the flow through the scour outlet, but reportedly raised its outlet level to 1,092 m (NamWater, 2004).
5.2.1.3 Hydrological Design The design and construction of the Calueque Dam was based on the flood peaks provided in Table 5.1 (LCE, 1992a).
Table 5.1: Design Flood Peaks for Calueque Dam (LCE, 1992a)
Return Period Flood Peak Remarks (Years) (m3/s)
1:15 2,000 Construction Flood
1:50 3,000 Normal Flood
1:100 3,600
1:500 5,000 Design Flood
1:10,000 8,000 Peak Maximum Flood
The 95% safe yield of the dam is reported to be 135 Mm3/a (DWA, 1991).
Chapter 5: Water Supply Infrastructure in the Cuvelai Area 5-6 THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
5.2.1.4 Raw Water Abstraction and Transfer With the dam incomplete, a skimming weir and a diversion canal presently divert river water to NamWater’s raw water pump station, which layout is shown schematically in Figure 5.6. Water can only be diverted to the pump station when the water level at the weir is higher than 1,088.17 m asl. The capacity of the diversion canal is 3 m3/s when the water level in the river at the skimming weir exceeds the weir level by 1.43 m, i.e. when it is at 1,089.60 m asl. With the stop logs in the scour outlet, this level is reportedly exceeded at all times (NamWater, 2004).
Figure 5.6: Layout of Skimming Weir and Diversion Canal at Calueque Dam (NamWater, 2004)
5.2.1.5 Storage Volume of Calueque Dam The stage-volume and stage-surface area graphs for Calueque Dam are provided in Figure 5.7. Assuming a water surface elevation of 1,092.0 m, following the insertion of stop logs in the scour outlet (NamWater, 2004), the storage capacity can be seen to be approximately 10 Mm3. This capacity is equivalent to storage for approximately 19 days at an abstraction rate of 6 m3/s (LCE, 2009).
Chapter 5: Water Supply Infrastructure in the Cuvelai Area 5-7 THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
Figure 5.7: Storage and Surface Area Curves of Calueque Dam (LCE, 1992a)
5.2.2 Calueque Pump Station
At the time of the assessment conducted for the Cuvelai Bulk Water Master Plan, the two pumps in the pump station were Mather & Platt 36”/36” BLEY vertical split, single stage, double suction pumps, which were driven by two BBC ZSM0229 electrical motors (shown in Figure 5.8) of 650 kW, 3.3 kV, 50 Hz each, which ran at a fixed speed of 494 rpm (LCE, 2009 and refer also to NamWater, 2004).
These pumps and motors each have a nominal capacity of 7,128 m3/h or 1.98 m3/s. However, at a dam level of 1,092 m, the installed pumping capacity per pump at a head of about 22 m is 1.9 m3/s. At the same dam level, with two pumps running simultaneously, the delivery amounts to 3.3 m3/s at a head of about 24 m (NamWater, 2004).
A previous report noted that in order to be able to increase the delivery capacity of the pumps, NamWater had acquired, but not yet installed, three new 1,200 kW Elmac motors running at 594 rpm and one additional pump. At a dam level of 1,092 m, with these new motors, the delivery capacity is expected to be 3.2 m3/s at 24 m for each pump. With two pumps and new motors running simultaneously, the delivery capacity would be 5.3 m3/s at a head of 29 m (NamWater, 2004). At the time of assessment of the Calueque Pump Station in August 2007, these pumps and motors had not yet been installed (LCE, 2009).
Chapter 5: Water Supply Infrastructure in the Cuvelai Area 5-8 THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
Figure 5.8: Calueque Pump Station: View Into Pump Well Showing the Electric Motors
5.2.3 Calueque Pipeline
The Calueque Pump Station delivers into a 2,437 m long, 1,600 mm diameter1 steel pipeline inside Angola, which transfers water over the watershed and delivers it into the Calueque – Border Canal. The design capacity of this pipeline is reportedly 6 m3/s, however this figure and its pressure class could not be confirmed since as-built drawings could not be located. The static head at the lowest point along the pipeline is 24.5 m (after NamWater, 2004). Depending on the water level in the Kunene River, the water must be elevated about 18 m over the watershed and the original design pumping head at the Calueque Pump Station was between 25 and 35 m depending on the water level in the dam and the number of pumps in operation (DWA, 1991).
This steel pipeline is laid on concrete pedestals to which the pipes are strapped (refer to Figure 5.9). The pipeline dips underground at the start of the canal. The pipes are joined by steel Viking Johnson-type flexible couplings. A surge tower has been constructed along the pipeline (LCE, 2009).
1 Presumably the nominal diameter. The pipeline diameter is also given as 1,658 mm (DWA, 1991).
Chapter 5: Water Supply Infrastructure in the Cuvelai Area 5-9 THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
Figure 5.9: Calueque Pipeline
5.2.4 Summary of the Raw Water Abstraction Capacity at Calueque
The capacity of the raw water abstraction and transfer infrastructure also has an influence of the security of supply, and is summarised in Table 5.2.
Table 5.2: Capacity of Raw Water Abstraction and Transfer Infrastructure at Caluque
Capacity Remarks / Infrastructure Component Condition / Assumption (m3/s) Reference Skimming Weir Water level must be greater than 1,088.17 m Unknown Diversion Channel Water level at 1,089.6 m at the Skimming Weir 3.0 NamWater, 2004 Raw Water Pumps Dam level at 1,092.0 m 1.9 NamWater, 2004 Calueque Pipeline Assumed capacity 6.0 NamWater, 2004
From Table 5.2 it can be seen that the skimming weir (expected), diversion channel and raw water pumps have a capacity less than the maximum allowable abstraction rate of 6 m3/s, and therefore may comprise bottlenecks to the abstraction and transfer of water to the Cuvelai area.
Chapter 5: Water Supply Infrastructure in the Cuvelai Area 5-10 THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
5.3 CALUEQUE – OSHAKATI CANAL
The Calueque Pipeline discharges into the Calueque – Oshakati Canal which transfers the water abstracted from the Kunene River into Namibia and as far as Oshakati over a distance of some 146 km in total. The Calueque – Oshakati Canal, which is lined along its entire length, is split into separate sections as follows:
1. Calueque – Border Canal, 2. Border – Olushandja Canal, 3. Olushandja – Ombalantu Canal, 4. Ombalantu – Ogongo Canal, 5. Ogongo – Oshakati Canal.
Although the forerunner of a portion of the present canal, the Outapi – Oshakati flood collection canal was started in 1960, construction of the Calueque – Oshakati Canal in its present form took place in stages, starting at Calueque in 1970, and ending at Oshakati in 1996 (LCE, 2009).
A schematic layout of the various components of the Calueque – Border Canal is shown in Figure 5.11.
Full details of the various portions and components of the Calueque – Oshakati Canal are contained in the Cuvelai (also CNWSA) Bulk Water Maser Plan, and are only summarised in Table 5.3.
Figure 5.10: Portions of the Calueque – Oshakati Canal
(l) Calueque – Border Canal (r) Ogongo - Oshakati Canal
Chapter 5: Water Supply Infrastructure in the Cuvelai Area 5-11 THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
Figure 5.11: Schematic Layout of the Calueque – Oshakati Canal (LCE, 2009)
Chapter 5: Water Supply Infrastructure in the Cuvelai Area 5-12 THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
Table 5.3: Summary of the Properties of the Calueque – Oshakati Canal
Lining Current Length Slope Component Shape Lining Depth Capacity1 (km) 1 : 3 (m) (m /s) 2 Calueque – Border Canal Trapezoidal Section 9.6 Trapezoidal 1.9 6,200 9.40 (10.0) Reinforced concrete slabs Parabolic Section 2.4 Parabolic sides with flat bottom 1.9 6,200 9.70 (10.0) Border – Olushandja Canal (Trapezoidal)
Border – Bifurcation 2.43 Trapezoidal Interlocking concrete panels 1.9 8,000 10.30 (10.0)
100 mm thick reinforced concrete Bifurcation - Olushandja PP (New) 3.6 Trapezoidal 1.9 10,000 6.4 (6.0) panels
50 mm thick unreinforced concrete Bifurcation - Olushandja PP (Old) 3.4 Trapezoidal 1.9 10,000 6.4 (6.0) panels
Olushandja – Ombalantu Canal
Section 1 (Olushanjda – Mahenene) 1.62 12,000 5.80 (4.5) 14.9 Trapezoidal with rounded Section 2 Deckwerk interlocking bricks 1.62 12,000 4.6 (4.5) corners Section 3 (Mahene – Ombalantu) 22.4 1.44 12,000 3.1 (3.2) Ombalantu – Ogongo Canal Trapezium Section Trapezoidal with circular bottom Interlocking bricks 1.35 6,666 1.40 (1.5) 34.0 Reinforced in-situ cast concrete 8,000 to Parabolic Section Parabolic 1.8 1.39 (1.5) slabs 15,000 Ogongo – Oshakati Canal Original: 75 mm thick unreinforced concrete lining. Trapezoidal Section 53.0 Trapezoidal 1.62 32,000 1.223 (1.3) Replacement: 100 mm thick reinforced concrete slabs Rectangular 1.0 Rectangular box culvert Inverted box culverts 1.5 15,000 1.403 (1.3)
Chapter 5: Water Supply Infrastructure in the Cuvelai Area 5-13 THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
Notes: 1. The rated design capacity of the canal sections is shown in parenthesis. The calculated design capacity allowing for the roughness and siltation of the canal sections was obtained from the Cuvelai Bulk Water Master Plan (LCE, 2009). 2. The capacity of the Border – Olushandja Canal is given as 10 m3/s. However, an assessment of the (illegal) irrigation off-takes along this canal in 2003 showed that the resulting outflows could be as high as 1.417 m3/s if all the siphon pipes are open and the water in the canal is at its maximum possible level (LCE, 2004). An abstraction of 1.417 m3/s represents nearly 24% of the allowable abstraction of 6 m3/s from the Kunene River. Significantly less water therefore reaches Namibia than is abstracted at Calueque Dam, without even allowing for seepage and evaporation losses along the canal, which fact should also be allowed for when examining the sufficiency of the raw water supply to the Cuvelai area. 3. This length is also given as 2.5 km (NamWater, 2004). 4. The calculated design capacity depends on the water levels of the trapezoidal and box culvert sections, as well as the numerous siphons and the downstream water levels (due to downstream hydraulic control) – refer to the Cuvelai Bulk Water Master Plan (LCE, 2009). In recent years there have been reports that the capacity of the canal was significantly less than the design capacity of 1.3 m3/s, and in fact as low as 0.8 m3/s (NamWater, 2004 and LCE, 2009).
5.4 OLUSHANDJA DAM AND THE ETAKA CANAL
5.4.1 Olushandja Dam
5.4.1.1 Background The Olushandja Dam, which was constructed between 1971 and 1974, is unique in that it was built across the watershed which separates the Oshana Olushandja and the Oshana Etaka. The dam basin was created by building an embankment either side of the watershed (North and South Walls respectively) in each of the oshanas (DWA, 1991 and LCE, 1992b). The distance between the embankments is given as 18 km, (LCE, 1992b), 19 km (DWA, 1991) and 22 km (LCE, 2009).
The full supply capacity of the Olushandja Dam is given as 42.3 Mm3 (LCE, 1992b and NamWater, 2004) and 42.5 Mm3 (DWA, 1991). The maximum depth of the dam, which is shallow due to the very flat terrain, is given as 4 m (maximum depth; DWA, 1991) and 4.5 m (maximum useful depth; NamWater, 2004).
The main purpose of the dam is to serve as an emergency source during times when supply from Calueque is interrupted (NamWater, 2004) and to act as a storage facility closer to the demand centres and to accommodate peak demands (LCE, 2009).
Irrigation is currently taking place on the western bank of the dam, between the northern bank of the dam and District Road DR3616.
5.4.1.2 Construction A siphon runs along the length of the North Wall and links the end of the canal from Calueque with the start of the canal to Outapi (Ombalantu). A pump station and inlet works is situated on the dam wall. Water can be pumped from the dam into the siphon (and therefore into the Ombalantu Canal) by means of the electrically driven pumps.
The southern wall incorporates outlet works consisting of a gated oshana outlet (2 gates) and a pump outlet (DWA, 1991).
Chapter 5: Water Supply Infrastructure in the Cuvelai Area 5-14 THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
The sluices for releasing water into the oshana are thought to be of the floating, self-regulating type. At the time of the assessments conducted for the Cuvelai Bulk Water Master Plan, it was found that although the sluices appear to be in good condition, they will require inspection and repair, and at least the control pipework will need to be repaired or replaced if they need to be put into operation again. Similarly, the sluice gates for releasing water into the Etaka Canal, although outwardly appearing to be in a good condition and the time, are thought to require inspection and repair before being put back into service (LCE, 2009).
Figure 5.12: Aerial View of Olushandja Dam
Ruanaca
Oshakati
Etaka Canal N
Some time ago, an electrically-driven pump station was constructed on the embankment by means of which water could be pumped out of the dam into the Etaka Canal during times when the water level in the dam was below the sluice gates. At the time of the aforementioned assessments, the pumps were found to have been removed (LCE, 2009).
Chapter 5: Water Supply Infrastructure in the Cuvelai Area 5-15 THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
Figure 5.13: North and South Walls of the Olushandja Dam
(l) Olushandja Dam North Wall (r) Olushandja Dam South Wall showing sluices
5.4.1.3 Characteristics of Olushandja Dam The characteristics of Olushandja Dam are provided in Table 5.4.
Table 5.4: Characteristics of Olushandja Dam (NamWater, 2004)
Elevation Percentage of Description (m) Capacity Water level when empty 1,101.5 Nil Water level when full 1,106.0 100% Minimum water level 2002 – 2004 1,104.9 41.5% Maximum water level 2002 - 2004 1,105.6 74.5% Minimum water level to allow gravity flow into the Etaka Canal 1,.104.8 38.1% Outflow level of sluices in South Wall Approx. 1,106 ---
The stage-volume and stage-surface area graphs for Calueque Dam are provided in Figure 5.14.
The very flat terrain is evident in the maximum water depth of 4.5 m in the dam. A comparison of the storage volume versus surface area characteristics of the Olushandja and Calueque Dams at maximum impoundment shows that the two dams have almost identical ratios; Calueque Dam has a ratio of 1.74 Mm3/km2 at an elevation of 1,094.95 m, whilst Olushandja Dam has a ratio of 1.75 Mm3/km2 at a water elevation of 1,106.5 m (refer to Figure 5.7 and Figure 5.14 respectively).
Chapter 5: Water Supply Infrastructure in the Cuvelai Area 5-16 THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
Figure 5.14: Storage and Surface Area Curves of Olushandja Dam (NamWater, 2004)
Note: The stage curve shown above, provided by NamWater, indicates a storage volume which is greater than the quoted value of 42.3 Mm3 (NamWater, 2004).
5.4.2 Etaka Canal
5.4.2.1 Background The Etaka Canal was originally constructed over 100 km between Eunda and Okahao (Ongandjera) as a flood water collecting system and the base for a second artery to carry water from the Kunene River into the Cuvelai area, to supply the populated areas of Tsandi (Uukualuthi) and Okahao. The 1968 Master Water Plan envisaged that this canal would be linked up to the bifurcation on the Mahenene – Olushandja Canal over a distance of 20 km. However, since the construction of this canal in the 1960s, the population growth in the areas around Tsandi and Okahao increased dramatically, requiring that additional water be piped into this area, and as a result, the Etaka Canal was never linked to the Mahenene – Olushandja Canal as envisaged (after DWA, 1968 and DWA, 1991).
5.4.2.2 Details of the Etaka Canal The Etaka Canal is a 130 km long (NamWater, 2004) earth canal (unlined), which starts at the South Wall of the Olushandja Dam near Onesi and runs in a south-easterly direction to Okahao and beyond. Figure 5.15 shows the start of the canal at the Olushandja Dam. This canal was previously used to provide water, mainly for livestock watering, to the communities between Olushandja and Okahao. However, in the past, due to very high seepage and evaporation losses, a very low portion of the water pumped into the canal reached the end. As a result, the Etaka Canal has not been in use for several years, and its possible future use will mostly likely only be as a drought relief measure.
Chapter 5: Water Supply Infrastructure in the Cuvelai Area 5-17 THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
The Etaka Canal currently belongs to the MAWF and NamWater only pumps water from Olushandja Dam into the canal on instruction and payment for the water.
Figure 5.15: Start of the Etaka Canal at the South Wall of the Olushandja Dam
The design capacity of the Etaka Canal is given as 1 m3/s (DWA, 1991).
5.5 WATER PURIFICATION PLANTS Water purification plants in the Cuvelai are located at Ruacana, Olushandja, Outapi, Ogongo and Oshakati and apart from size, these also differ in configuration.
The operation of the Ruacana Purification Plant, and particularly the clarifiers and dosing system, has always been problematic. In 1996, NamWater recommended that the plant be abandoned on completion of the new Olushandja Slow Sand Filtration Purification Plant. Prior to this, the Ruacana Purification Plant was run at full capacity in order to meet the demand of Ruacana Town. Following the completion of the new Olushandja Purification Plant, very little maintenance work was done on the Plant, thus allowing it to deteriorate further. In 2007, NamWater decided to take the plant out of commission as Ruacana Town was then supplied from the Olushandja Purification Works (LCE, 2009).
The old batch plant at Outapi has also been taken out of operation and the plant now in operation is the “new” package plant.
Chapter 5: Water Supply Infrastructure in the Cuvelai Area 5-18 THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
Table 5.5: Summarised Details of the Purification Plants in the Cuvelai Area (LCE, 2009)
Date Capacity Location Type of Plant, Infrastructure and Processes Constructed (m3/h) Batch purification plant Olushandja (old) Building, raw water pumps, chemical dosing, four batch settlers, Late 1970s 13.331 potable water pumps, reservoir, disinfection Slow Sand Filtration A pump station comprising various raw water and treated water Olushandja (new) pump sets, an elevated raw water reservoir, from which the 2000 33.332 Roughing Filters are supplied under gravity, two roughing filters, two slow sand filtration filters, a treated water reservoir (or sump) Continuous purification process Ruacana Including chemical dosing, flash mixing, flocculation, settling, 1970s 523 filtration and disinfection Package plant A pump station housing various raw water and potable water pump sets, a prefabricated treatment plant comprising flashmixers, a flocculator and settling tanks, a bank of pressure filters, a reinforced concrete potable water reservoir, an elevated Outapi reservoir, a bank of five sludge lagoons and a raw-water storage N/A 1054 (Ombalantu) dam. Pre-chlorination, flashmixing, coagulation, flocculation, sedimentation and filtration. Other activities include chemical storage, chemical preparation and dosing, waterworks sludge disposal, with recirculation of the supernatant. A forebay into which the canal from Ombalantu discharges, a raw water pumping station at the forebay, a flashmixer, three Ogongo clariflocculators, six pressure filters, treated water reservoir, Early 1980s 1,2005 potable water pump station, sludge lagoons, a chemical dosing and administration building, and operators’ accommodation Conventional design Unit processes of pre-chlorination, coagulation, flocculation, sedimentation, intermediate chlorination, filtration, stabilisation (pre- and post-lime dosing) and post chlorination. Other activities Oshakati 1996 1,6676 include chemical storage, chemical preparation and dosing, lime saturation, sludge recycling, filter backwash recovery and waterworks sludge disposal in lagoons, with the recirculation of supernatant
Notes: 1. Capacity based on a design value of 3,200 m3/d over a 24-hour day. 2. Capacity based on a design value of 800 m3/d over a 24-hour day. 3. Capacity based on an actual value of 52 m3/h, although the plant is no longer in operation. 4. Capacity based on a 22-hour day. 5. Operator-indicated capacity of the plant (The design capacity of the Ogongo Purification Plant is 30,000 m3/d. The Water Treatment Sub-Division of NamWater has recommended that the capacity of the plant should be taken as 20,000 m3/d due to the “poor design of the clariflocculators and the dosing equipment”, and the incorrect filter media in two of the sand filters. However, according to the operator, the capacity of the plant is approximately 1,200 m3/h (LCE, 2009).
Chapter 5: Water Supply Infrastructure in the Cuvelai Area 5-19 THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
6. Plant capacity of 40,000 m3/d over a 24-hour day (average clean water flow). The peak flow capacity is 50,000 m3/d (2,083 m3/h over 24 hours). The layout of the plant is such that the capacity can be doubled up in future.
5.6 NAMWATER’S PIPELINES, PUMP STATIONS AND RESERVOIRS 5.6.1 Extent of NamWater’s Bulk Transfer Infrastructure
The extent of NamWater’s bulk transfer infrastructure in the Cuvelai area, as assessed using the WaterCAD hydraulic (numerical) model set up under the Cuvelai Bulk Water Master Plan is shown in Table 5.6.
Table 5.6: Extent of NamWater’s Bulk Water Supply Infrastructure in the Cuvelai Area (LCE, 2009)
Infrastructure Component Unit Quantity
Dams No. 1
Forebays1 No. 3
Canals2 km 146
Purification Plants3 No. 5
Pump Stations4 No. 37
Pump Sets5 No. 106 Reservoirs (GLR + ER)6 No. 48 Pipeline Segments No. 739 Pipeline Length km 1,359 Volume of water in reservoirs (full) m3 50,403 Volume of water in pipelines m3 106,369
Notes: 1. Olushandja, Oshakati & Ogongo. 2. Excluding the Etaka Canal. 3. Ruacana, Olushandja, Outapi, Ogongo and Oshakati. 4. Pump station locations. 5. Number of pump sets – individual pumps or groups of pumps. 6. Only those simulated in the WaterCAD model.
The location of the canals, pump stations, “bulk” and “rural” pipelines (refer below) is shown in Figure 5.3.
5.6.2 Capacity of the Major Pipeline Arteries
The capacities of all NamWater’s bulk transfer pipelines, in conjunction with the associated pump stations, are provided in the Cuvelai Bulk Water Master Plan. Since the capacities of many of these pipelines are not pertinent to this Study, only the capacities of the major, inter- zone transfer pipelines are shown in Table 5.7.
It should be noted that the capacity values shown are those for the pipeline and pump station combinations, as modelled using the WaterCAD hydraulic (numerical) model set up under the Cuvelai Bulk Water Master Plan
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Table 5.7: Capacity of the Major Pipeline Arteries in the Cuvelai Area (LCE, 2009)
Capacity Zone Pump Station / Pipeline (m3/h)
Olushandja – Eunda1 82.5
2 Olushandja – Ruacana 157.0
Olushandja – Ruacana Booster 121.7
Okahao – Tsandi 157.8 4 Tsandi – Eunda 64.4
Ogongo Pumps2 614.9 5 Omungwelume Pumps 30.9 Oshakati – Ondangwa (Old) 720 6 Ongwediva 200 Oshakati – Ondangwa3 1,100 Oshakati – Omakango 569.6 Omakango – Omafo 335 7 Omafo – Omungwelume 29.8 Omafo – Oshikango 100.7 Omafo – Eenhana4 195.8 Omafo – Eenhana4 293.7 Ondangwa – Southeast 776.6 Oshali 433.3 8 Okatope 257.5 Omutsegwonime 64.1 Notes: 1. It was assumed that this system will be decommissioned once the new Tsandi RWSP is in operation. 2. As these pumps supply water to Zones 4 & 5; the water demands used include both zones and not the pump operational settings. 3. For the WaterCAD simulations carried out for the Cuvelai Bulk Water Master Plan, the Iindangungu – Omakango Pipeline was divided such that Ongha is supplied from Omakango and the Iindangungu – Omakango RWS off-take is supplied from Iindangungu. 4. For the WaterCAD simulations carried out for the Cuvelai Bulk Water Master Plan, it was determined that although the Omafo – Eenhana pumps have the flow capacity, they do have sufficient pressure to meet the demand.
5.7 RURAL WATER SUPPLY PIPELINE SCHEMES
In calculating the rural water demands in the Cuvelai for the 2009 Bulk Water Master Plan, the rural (non-urban) areas of the Cuvelai were divided into 30 scheme service areas, which denote the areas served by the various water supply schemes (refer also to Chapter 7). For the CRRWSDP, these service areas were further delineated into sub-services areas in order to further isolate individual areas served by each rural water supply scheme. In a manner similar to that done for the Bulk Water Master Plan, a WaterCAD hydraulic (numerical) model was then created for each of the different rural water supply schemes in the Cuvelai area in order to assess their current and future capacity. As the scope of this Study does not include an assessment of the rural water supply schemes, only a summary of the extent of this infrastructure is provided in Table 5.8.
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Table 5.8: Extent of the Rural Water Supply Pipeline Schemes (LCE, 2011)
Infrastructure Component Unit Quantity
Pipeline Segments No. 4,413
Pipeline Length km 4,873
Volume of water in pipelines m3 32,560
5.8 EXTENT OF THE BOREHOLE INFRASTRUCTURE
5.8.1.1 Information Obtained under the Combined Regional Rural Water Supply Development Plan With the compilation of the CRRWSDP, information on the boreholes in the Cuvelai area was obtained from the “Groundwater Investigation in the Cuvelai-Etosha Basin” project as well as from sample assessments carried out in the Omusati Region (western portion) and the Ohangwena and Oshikoto Regions (eastern portion). This groundwater investigation project is a 3-year project within the framework of German-Namibian Technical Cooperation, concluded between the Republic of Namibia and the Federal Republic of Germany. The project partners for this initiative are the Federal Institute for Geosciences and Natural Resources (BGR) and the Department of Water Affairs and Forestry (DWAF) in the Ministry of Agriculture, Water and Forestry. The project activities are closely linked to the DWAF-GTZ project “Integrated Land and Water Management in the Cuvelai Basin” (LCE, 2011).
The DWAF – BGR Groundwater Project intends to investigate the distribution of fresh and saline groundwater and to determine the characteristics of the aquifers within the Cuvelai- Etosha Basin by a combination of geophysical and hydrogeological methods. This project had at the time assessed 923 boreholes during a hydrocensus, which information, modified with the removal of monitoring boreholes, blocked / collapsed and abandoned / destroyed boreholes, was incorporated into a database of the boreholes in the Cuvelai area created under the CRRWSDP project.
Under the CRRWSDP, a total of 113 boreholes were visited and assessed for verification of the information in the database; 54 boreholes in the Omusati Region, 26 in the Ohangwena Region and 33 in the Oshikoto Region. No rural water supply borehole installations are located in the Oshana Region, due to the salinity of the groundwater.
5.8.1.2 Extent of the Borehole Infrastructure The location and different types of borehole water supply installations in the Omusati Region are shown in Figure 5.16.
Chapter 5: Water Supply Infrastructure in the Cuvelai Area 5-22 THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
Figure 5.16: Location and Type of Borehole Water Points in the Omusati Region (LCE, 2011)
The location and different types of borehole water supply installations in the Ohangwena and Oshikoto Regions are shown in Figure 5.17.
Figure 5.17: Location and Type of Borehole Water Points in the Ohangwena and Oshikoto Regions (LCE, 2011)
Chapter 5: Water Supply Infrastructure in the Cuvelai Area 5-23 THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
CHAPTER 6 : HISTORIC WATER CONSUMPTION IN THE CUVELAI AREA
6.1 WATER CONSUMPTION AND HISTORIC SALES DATA 6.1.1 Pipeline and Borehole Potable Water Use
The Cuvelai area investigated under this Study is primarily that area served by the central pipeline network, which is shown in Figure 5.1 (refer also to Figure 5.3 and Section 1.2.2). On this basis, the historic consumption analysed is that supplied via NamWater’s network of bulk pipelines. Consumption which is supplied via the DWSSC’s network of rural water supply schemes is included, at this is reflected as water sold by NamWater either to the DWSSC, or to the rural community (feederline or local water committees or private consumers) directly. Water consumption supplied by the individual borehole installations in the western and eastern parts of the Cuvelai is not included, firstly because this is not the primary focus of this Study and secondly because this information is not readily available.
6.1.2 Irrigation Water Irrigation water used at the Etunda (Green Scheme) Irrigation Project is analysed separately, since it is not supplied via the pipeline network, but from the Calueque – Oshakati Canal directly (raw water), upstream of the Olushandja Dam and because Etunda is the single largest water consumer in Namibia.
6.1.3 NamWater’s Historic Sales Data NamWater provided the Consultant with electronic data of the monthly billed consumption of users in the Cuvelai area for the period February 1997 to March 2013 (therefore that of consumers supplied and billed by NamWater). This data is sourced from the billing database maintained by the Finance Department of NamWater.
The data represents the volume of water for which consumers have been billed and for which the billed consumption has been entered into the NamWater billing database. It is assumed that that the volumes in the billing data represent the water consumption of users.
The data provided consists of a number of fields of which the consumption group category, customer name and scheme definition were the most pertinent to this Study.
The accuracy of the analyses of the historic water consumption, the number of consumers in the Cuvelai area and the Cuvelai area water balance are dependent on the accuracy of the data provided by NamWater.
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6.2 HISTORIC WATER CONSUMPTION
6.2.1 Historic Monthly Consumption
The total water consumption in the Cuvelai area, excluding irritation, has generally remained stable over the period for which data is available. A slight decreasing trend is observed between April 1999 and April 2007, and an increasing trend is observed from approximately April 2009 onwards, as illustrated in Figure 6.1.
According to the data, peak consumption occurs during September, October, November, January and in May, as illustrated in Figure 6.2. December’s lower consumption is highly unlikely, as this occurs during the hot summer period and coincides with the festive season and holiday period, with an influx of holiday goers from other parts of Namibia. The lower consumption can most likely be attributed to early water meter readings during December to accommodate for the holiday period for NamWater personnel, where some of December’s consumption is incorporated into January (p 4-5; LCE, 2009).
Figure 6.1: Monthly Water Consumption for the Whole Cuvelai Area, Excluding Irrigation
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Figure 6.2: Distribution of Monthly Sales Volumes as a Percentage of Total Volume for the Cuvelai Area, Excluding Irrigation
6.2.2 Historic Annual Consumption
The historic annual consumption (for NamWater’s April – March financial years) shows a similar trend to that of the monthly consumption; a general decreasing trend from 1999/00 to 2007/08 and an increasing trend from 2009 onwards, as illustrated in Figure 6.3. The consumption of April 2012 to March 2013 was the highest on record at almost 12 Mm3/a. The increasing trend can be attributed to an increase in the number of people gaining access to potable water through water infrastructure development in recent years (refer to Section 6.3).
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Figure 6.3: Annual Sales Volumes for the Whole Cuvelai Area, Excluding Irrigation
6.2.3 Water Consumption by Consumer Category The total water consumption of the whole Cuvelai area has been divided into the following categories of use, based on the NamWater billing data “group” categories and modified slightly for the purposes of this Report:
Industry, Private Consumers, Irrigation Schemes, Ministerial, being all Government Ministries, Not Maintained, Regional Councils, Rural Water Community, Town and Village Councils and Municipalities.
The “Not Maintained” category has only become relevant since 2007, where the category was used for the first time in the billing data and has grown rapidly since. Although the category represents at its peak only 0.16% of the total sales, it was nevertheless included in the analysis for the sake of completeness.
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Table 6.1 and Table 6.2 indicate the annual consumption per defined category in terms of water volume and in terms of proportion of total sales, which latter distribution is summarised graphically in Figure 6.4. From this figure it is clear that demand categories have changed over the period analysed, with Town and Village Council and Municipalities accounting for between 40% and 50% of the total consumption by volume. Although the Ministerial category initially made up more than a third of consumption in 1997/98, it has declined significantly to about 12% of the total by 2012/13. By contrast, the Private Consumer category has increased significantly, from approximately 3% of the total in 1997/98 to more than 14% in 2012/13, whilst similar trends are observed for the Rural Water Community category. The Industry and Regional Council categories have remained largely stable, whilst the Not Maintained category, though increasing, remains largely insignificant.
Figure 6.4: Proportion of Sales Volumes per Consumption Category, Excluding Irrigation (Percentage of the Total)
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Table 6.1: Consumption in the Cuvelai Area by Different Categories per Volume, Excluding Irrigation
Annual Consumption (Mm3/a) Town and Village Year Private Rural Water Industry Ministerial Not Maintained Regional Council Council and Consumer Community Municipalities 1997/98 0.12 3.30 0.00 0.30 0.37 0.04 4.92 1998/99 0.27 3.88 0.00 0.39 0.58 0.04 5.35 1999/00 0.32 4.53 0.00 0.48 0.56 0.31 5.08 2000/01 0.20 4.07 0.00 0.68 0.69 0.66 4.66 2001/02 0.26 3.96 0.00 0.64 0.66 0.64 4.33 2002/03 0.31 3.40 0.00 0.73 0.65 1.40 4.55 2003/04 0.36 3.44 0.00 0.75 0.59 1.04 4.56 2004/05 0.42 2.52 0.00 0.78 0.68 0.96 4.61 2005/06 0.49 2.86 0.00 0.73 0.60 1.10 4.42 2006/07 0.26 2.59 0.00 0.75 0.63 0.98 4.49 2007/08 0.37 3.59 0.00 1.20 0.48 0.93 4.56 2008/09 0.17 1.83 0.00 0.91 0.75 0.74 4.99 2009/10 0.22 1.72 0.01 1.00 0.58 0.95 5.44 2010/11 0.27 1.81 0.01 1.13 0.46 0.97 5.35 2011/12 0.29 1.83 0.01 1.18 0.65 1.34 5.84 2012/13 0.24 1.52 0.02 1.75 0.58 1.78 6.09 Average 0.29 2.93 0.00 0.84 0.59 0.87 4.95
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Table 6.2: Consumption by Different Categories as a Percentage of the Total for the Cuvelai Area, Excluding Irrigation
Percentage of Total Consumption (%) Per Consumer Category Per Year
Town and Village Year Private Regional Rural Water Industry Ministerial Not Maintained Council and Consumers Council Community Municipalities 1997/98 1.37 36.42 0.00 3.32 4.13 0.41 54.36 1998/99 2.58 36.93 0.00 3.68 5.49 0.39 50.93 1999/00 2.84 40.15 0.00 4.28 5.00 2.73 45.01 2000/01 1.81 37.19 0.00 6.17 6.29 6.05 42.49 2001/02 2.45 37.82 0.00 6.07 6.28 6.10 41.28 2002/03 2.81 30.79 0.00 6.57 5.93 12.71 41.19 2003/04 3.37 32.01 0.00 6.98 5.51 9.66 42.47 2004/05 4.19 25.28 0.00 7.85 6.79 9.62 46.27 2005/06 4.82 27.99 0.00 7.18 5.87 10.81 43.33 2006/07 2.70 26.71 0.00 7.72 6.50 10.09 46.28 2007/08 3.28 32.27 0.00 10.82 4.28 8.37 40.98 2008/09 1.79 19.51 0.01 9.72 7.93 7.91 53.14 2009/10 2.26 17.33 0.08 10.05 5.85 9.55 54.89 2010/11 2.71 18.09 0.13 11.31 4.60 9.74 53.43 2011/12 2.62 16.39 0.13 10.55 5.85 12.02 52.44 2012/13 2.03 12.69 0.16 14.59 4.88 14.84 50.82 Average 2.73 27.97 0.03 7.93 5.70 8.19 47.46
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The water consumption by the Ministerial category was also analysed in greater detail. The various Ministries included in the NamWater billing data are as follows:
Ministry of Agriculture, Water and Forestry (MAWF), Ministry of Defence (MoD), Ministry of Education (MoE), Ministry of Fisheries and Marine Resources (MFMR), Ministry of Health and Social Services (MHSS), Ministry of Home Affairs and Immigration (MHAI), Ministry of Lands and Resettlement (MLR), Ministry of Ministry of Regional, Local Government and Housing and Rural Development (MRLGHRD), Ministry of Safety and Security (MSS),
Some of the Ministries could not be clearly identified and were categorised as “Uncertain”. It should be noted that any irrigation-related consumption identified under the MAWF sub- category was categorised as irrigation usage
As illustrated in Figure 6.5 for annual water sales per ministerial category, Ministerial sales have declined from approximately 5 Mm3/a at their peak in 1999/00 to approximately 1.8 Mm3/a in 2012/13; a 65% decline. The decline is mainly attributed to the decrease in demand by the MAWF, as they were previously invoiced by NamWater on behalf of rural communities, and increasingly these communities are being billed directly by NamWater (via feederline or local water committees, or via individual private off-takes).
Figure 6.5: Annual Sales Volumes to Ministerial Customers in the Cuvelai Area
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The other Ministries have a largely insignificant effect on the total Ministerial sales, except for the MoE, to whom sales have showed continual growth since the start of the period.
6.2.4 Urban and Rural Water Consumption
Water sales data was summarised into “urban” and “rural” categories, excluding the irrigation usage. Urban areas were so defined according to the defined urban areas listed in Section 7.4.1. All other sales data, with the exception of the irrigation volumes, were considered “rural”. Table 6.3 and Figure 6.6 illustrate the total annual sales volumes categorised according to urban and rural consumption.
Table 6.3: Annual Urban and Rural Sales Volumes for the Cuvelai Area
Water Sales Volumes
Year (Mm3/a)
Urban Rural
1997/98 4.61 4.45
1998/99 5.20 5.30
1999/00 4.71 6.57
2000/01 4.17 6.78
2001/02 4.36 6.12 2002/03 4.70 6.34 2003/04 4.70 6.05 2004/05 4.82 5.14 2005/06 4.70 5.51 2006/07 4.80 4.89 2007/08 4.86 6.27 2008/09 5.63 3.77 2009/10 6.00 3.93 2010/11 5.74 4.26 2011/12 6.46 4.68 2012/13 6.11 5.86 Average 5.10 5.37
An increase in the urban water consumption from 2010/11 onwards is noticeable, whilst the increased rural water consumption in 2012/13 can be attributed to drought conditions during the 2012/13 rainy season.
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Figure 6.6: Annual Urban and Rural Water Sales for the Cuvelai Area (Mm3/a)
6.2.5 Irrigation Water Consumption
Irrigation takes place at three schemes in the Cuvelai area, namely the Etunda, Ogongo and Mahenene irrigation schemes. The annual consumption of each scheme is listed in Table 6.4. It is clear that the Etunda irrigation scheme is the major consumer of irrigation water in the Cuvelai area. Whilst both the Ogongo and Mahenene schemes are orders of magnitude smaller than the Etunda scheme, the Mahenene scheme has shown low to zero consumption since 2006/07.
The total irrigation water consumption is illustrated in Figure 6.7. The irrigation consumption shows a large variance, ranging between 4.00 and 10.00 Mm3/a. The reason for the high annual variability in the consumption, like between 2005/06 and 2007/08 and between 2011/12 and 2012/13, is not certain, and no additional data could be provided by the MAWF to allow this to be investigated further.
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Table 6.4: Irrigation Sales Volumes per Irrigation Scheme in the Cuvelai Area (Mm3/a)
Irrigation Sales Volumes (Mm3/a) by Scheme Total Date Etunda Ogongo Mahenene (Mm3/a) 1997/98 3.44 0.29 0.28 4.00 1998/99 3.02 0.30 0.28 3.60 1999/00 4.63 0.28 0.28 5.18 2000/01 5.18 0.22 0.28 5.68 2001/02 5.02 0.19 0.28 5.49 2002/03 6.79 0.21 0.28 7.28 2003/04 8.89 0.25 0.20 9.35 2004/05 8.32 0.23 0.24 8.79 2005/06 9.12 0.27 0.20 9.60 2006/07 4.78 0.19 0.00 4.96 2007/08 9.21 0.13 0.00 9.34 2008/09 8.22 0.09 0.00 8.31 2009/10 7.99 0.09 0.00 8.08 2010/11 7.43 0.09 0.06 7.58 2011/12 5.05 0.11 0.00 5.16 2012/13 10.42 0.10 0.13 10.66 Average 6.72 0.19 0.16 7.07
Figure 6.7: Total Irrigation Water Use in the Cuvelai Area (Mm3/a)
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6.3 NUMBER OF WATER CONSUMERS IN THE CUVELAI AREA
6.3.1 Determination of the Number of Billed Consumers
In the billing database provided by NamWater, “zero” monthly sales entries have been assumed to be due to that consumer’s water meter not being read, or that consumer not being billed (through NamWater’s “system”) for that particular month. In determining the number of billed consumers, such zero entries have not been included, such that the number of billed consumers for a particular month is defined as the number of non-zero water sales entries for that month.
Consumers may or may not be billed in any given month, as most likely occurs in Decembers and Januaries, as noted above. The number of consumers billed in each month of the year cannot merely be added to determine the number of consumers billed in a given year, as most consumers should be billed every month. For this reason, the average number of billed consumers has been determined as the average of the number of billed consumers for the twelve months of the year.
6.3.2 Number of Billed Consumers
The number of billed consumers per month in the Cuvelai area has shown a twenty one-fold increase from a total of 509 in April 1997 to 11,032 in March 2013, as illustrated in Figure 6.8. The period from April 1997 to April 2004 shows a stable, near linear increase, whilst the following period shows greater variance and non-linear growth up until March 2013.
The reason for this increase in the overall number of consumers is the strong increase in the number of private consumers since the start of the period, which consumers constitute the majority of the total number of consumers, as indicated in Table 6.5 and illustrated graphically in Figure 6.9.
The Private Consumers category constitutes, on average, 77.87% of the number of consumers, whilst consuming on average 7.93% of the potable water by volume. Although this percentage of the volumetric consumption is increasing (refer to Table 6.1), the operational implications of this miss-match represents significant challenges to NamWater.
The sharp increase in the number of private consumers is tied to the decline in the volumetric consumption of the MAWF in the Ministerial category (refer to Figure 6.5). Following the completion of rural water supply schemes by the DWSSC and its forerunners in the MAWF, NamWater initially invoiced the MAWF on behalf of the rural communities. In time, the feederline committees and local water committees were invoiced by NamWater directly, hence the decline in sales to the MAWF and a slow increase in the number of private consumers. With increasing prosperity in recent years, the rural communities have applied for private connections to be able to supply their households directly, in lieu of collecting water at the communal water point installations (as per the initial scheme configuration). This trend, in particular since about 2010, is a large part of the reason behind the accelerated increase in private consumers billed by NamWater.
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Figure 6.8: Total Number of Billed Consumers per Month in the Cuvelai Area
Note: Numbers do not include the zero entries in the NamWater sales data.
Table 6.5: Billed Consumers in Different Categories as a Percentage of the Total
Percentage of Average Annual No. of Billed Consumers (%) Per Consumer Category Per Year Town and Year Not Private Regional Rural Water Village Industry Ministerial Maintained Consumers Council Community Council and Municipalities 1997/98 3.13 11.21 0.00 72.98 1.35 0.35 10.98 1998/99 4.00 8.76 0.00 77.01 1.33 0.37 8.51 1999/00 3.73 12.99 0.00 74.53 0.90 2.21 5.64 2000/01 2.96 13.46 0.00 75.52 0.71 2.57 4.77 2001/02 2.76 13.32 0.00 76.21 0.59 2.54 4.58 2002/03 2.59 12.80 0.00 76.60 0.55 3.16 4.30 2003/04 2.60 17.78 0.00 70.88 0.51 4.50 3.73 2004/05 2.55 15.68 0.00 73.30 0.50 4.29 3.69 2005/06 2.19 14.91 0.00 74.13 0.50 4.53 3.74 2006/07 1.86 13.13 0.00 76.77 0.51 4.10 3.63 2007/08 1.70 11.57 0.00 78.73 0.55 4.09 3.36 2008/09 1.74 10.51 0.12 80.40 0.50 3.52 3.20 2009/10 1.46 9.65 0.43 81.59 0.47 3.67 2.73 2010/11 1.43 7.79 0.69 83.78 0.39 3.47 2.44 2011/12 1.28 6.51 0.80 85.52 0.32 3.29 2.27 2012/13 0.99 5.45 0.71 87.97 0.25 2.87 1.75 Average 2.31 11.60 0.17 77.87 0.62 3.10 4.33
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Figure 6.9: Average Annual Number of Billed Consumers per Category in the Cuvelai Area
Note: Numbers do not include the zero entries in the NamWater sales data.
6.4 WATER BALANCE FOR THE CUVELAI AREA
6.4.1 Volumes Abstracted at the Calueque Dam
The monthly volumes pumped from the Kunene River at Calueque (refer to Section 5.2.1) between January 2005 and June 2013 were provided by NamWater, is illustrated in Figure 6.10. The average monthly abstraction volumes, averaging 4.93 Mm3/a (2.28 m3/s), generally range between 4 and 6 Mm3/a, with some notable exceptions, for instance the low volumes during April and May 2011, for which no reason was provided. The conversely high abstraction values immediately thereafter may however suggest a water meter or data entry error of some nature.
The abstraction volumes at Calueque serve as the sole input of water into the Cuvelai area and can thus be directly compared with the water sales (consumption) in the Cuvelai in order to provide a water balance for the area.
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Figure 6.10: Monthly Abstraction at Calueque (Mm3/m)
6.4.2 Comparison of the Water Abstraction and Water Sales
The volumes of water abstracted from the Kunene River at Calueque were compared with the Cuvelai sales (consumption) data (including irrigation water) for the period between April 2005 and March 2013, which is the period of overlap between the two datasets (for full NamWater financial years). The difference between the abstraction volumes (or input into the Cuvelai “system”), and the billed sales data in the Cuvelai is the volume of water for which NamWater does not receive payment, thus termed non-revenue water (NRW). Figure 6.11 illustrates the total annual billed consumption per customer category and the total non-revenue water.
Table 6.6 indicates the volume of NRW and the proportion of this relative to the total abstracted volume. Both the total and proportion of NRW have shown a general decrease over the period, with the values for 2012/13 being the lowest over the period. The drop in NRW could be attributed to better water management practices carried out by NamWater, increased billing efficiency, decreased use of reserve storage at Olushandja Dam, or could be due to other factors, and further investigation would be required to establish the exact cause of the decrease.
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Figure 6.11: Comparison of Annual Inflow into- and Consumption Volumes in the Cuvelai Area
Table 6.6: Volume of Non-Revenue Water and Percentage of the Total Volume Abstracted at Calueque
Non-Revenue Water
Portion of Calueque Year Total Volume Abstraction (Mm3/a) (%)
2005/06 43.25 68.6
2006/07 45.25 75.5
2007/08 43.95 68.2
2008/09 42.61 70.6
2009/10 36.93 67.2
2010/11 45.70 72.2 2011/12 35.00 68.2 2012/13 32.86 59.2 Average 40.69 68.7
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The NRW is most likely made up of water lost due to:
1. Seepage losses along the canals and at dams (“dams” would include pumped storage dams and forebays, and particularly Olushandja Dam), 2. Evaporation losses from the canals and dams, particularly at Olushandja Dam, 3. Illegal off-takes from the Calueque – Border Canal, 4. Illegal off-takes from pipelines within the Cuvelai area, 5. Unbilled consumption from formal off-takes within the Cuvelai area, 6. Leaks and other losses (like pipe breaks and purification plant losses) within the Cuvelai area.
Under the Cuvelai Bulk Water Master Plan (BWMP; LCE, 2009), it was estimated that the major contributor to NRW is evaporation losses, accounting for nearly 65% of all NRW, followed by illegal off-takes from the Calueque – Border Canal, accounting for nearly 20% of non-revenue water.
Figure 6.12 illustrates the relationship between the annual proportion of non-revenue water (taken as the portion of the total abstraction at Calueque) and the total annual sales data, both including and excluding irrigation consumption. In both cases, there is some indication that the proportion of non-revenue water decreases with an increase in consumption (sales). The linear regression lines and the corresponding R2 values were added for illustrative purposes only, as the linear relationship cannot be extrapolated to much higher consumption values, otherwise the non-revenue water proportion would be reduced to zero, which is not considered practical.
Figure 6.12: Relationship between the Proportion of the Non-Revenue Water and the Total Consumption Values, Including and Excluding Irrigation Consumption
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CHAPTER 7 : WATER DEMANDS IN THE CUVELAI AREA
7.1 OVERVIEW OF THE ESTIMATION OF THE WATER DEMANDS
This Chapter describes the basic methodology according to which the water demands for the Cuvelai area were estimated, using a similar methodology to and the same basic principles as that implemented under the Water Supply Infrastructure Development and Capital Replacement Master Water Plan for the Central North Water Supply Area (LCE, 2009) (henceforth referred to as the 2009 Cuvelai BWMP). Some data from the 2009 BWMP has also been used where applicable.
General comments on and principles regarding water demand forecasts are provided in Section 2.6.
Water demands in the Cuvelai area have been prepared on a theoretical basis for urban, rural and irrigation demands separately (segregated demand). Population figures from the latest 2011 Census were assessed in order to establish suitable growth rates for the Cuvelai area (refer to Section 2.3, Section 3.1.4 and Section 7.2) and potential future developments in the Cuvelai area were considered (refer to Section 7.3). Urban water demands were determined based on the number of people in each urban settlement and the extent of institutions, businesses and other commercial enterprises (Section 7.4). Rural water demands were based on the numbers of rural-dwelling people, livestock and the size and number of schools and clinics (Section 7.5), whilst the irrigation demand is based on the area that is irrigated (Section 7.7). Finally, the required theoretical abstraction from the Kunene River at Calueque was calculated from the current and projected future water demands (refer to Sections 7.8 and 7.9).
7.1.1 Zonal Division
The water demands for the Cuvelai area were calculated individually for each of the eight Water Supply Zones, which are illustrated in Figure 7.1 (refer also to Section 5.1 regarding the water supply zones).
7.1.2 Demand Scenarios
Three scenarios were used for the water demand projections, namely low likely, likely and high likely scenarios. The likely scenario describes the most likely theoretical demands based on the expected population growth and development prospects. The low likely and high likely scenarios describe the lowest and highest expected population growth and development prospects. Table 7.1 provides further details on each scenario.
7.1.3 Water Demands and Losses
Water demand values were estimated by selecting an adopted theoretical demand value for the current year of 2012/13 for the urban, rural and irrigation demands, and all future theoretical demand projections for all three scenarios used the adopted demand as a base value. (Sections 7.4 to 7.7)
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Water losses were estimated by adding distribution losses to the water demands, to obtain the water supply requirements for the Cuvelai area. Total abstraction requirements were estimated by adding a non-revenue water portion to the theoretical demands (refer to Section 7.9).
Figure 7.1: Water Supply Zones of the Cuvelai Area
Table 7.1: Water Demand Scenario Details
Water Demand Scenario Factor Low Likely Likely High Likely Population growth prospects Realistic population growth Population growth slightly Growth low, with little economic change prospects, based on 2011 higher than likely scenario, prospects to the current situation Census results with economic growth No additional water supply Incorporate likely supply Incorporate all known Scheme schemes and irrigation schemes to be completed in schemes that are currently expansion demands incorporated the near-future planned Current non-revenue Current non-revenue Current non-revenue Non-revenue proportions greatly reduced proportions slightly reduced proportion to remain near- water over time over time constant over time
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7.2 POPULATION AND POPULATION GROWTH RATES
7.2.1 Total Population and Growth Rates
A summary of the population totals and the growth rates in the Ohangwena, Omusati, Oshana and Oshikoto Regions is shown in Table 7.2. All values are from 2011 Census Report (NSA, 2012).
Table 7.2: Summary of Overall Population and the Population Growth Rates in the Ohangwena, Omusati, Oshana and Oshikoto Regions (NSA, 2012)
Total Population per Region Category Total Ohangwena Omusati Oshana Oshikoto Total 2001 228,384 228,842 161,916 161,007 780,149 Population 2011 245,446 243,166 176,674 181,973 847,259 Growth: % increase 7.47% 6.26% 9.11% 13.02% 8.60% 2001 - 2011 Growth rate1 0.72% 0.61% 0.88% 1.23% 0.83% Census 1991 - 2001 2.4% 1.9% 1.8% 2.2% Growth Rates1 2001 - 2011 0.7% 0.6% 0.9% 1.2%
1. Annualised growth rate
The total population in the four regions increased from 780,149 in 2001 to 847,259 in 2011. The population growth rate between 1991 and 2001 ranged between 1.8% and 2.4% for the four regions, whereas the growth rate between 2001 and 2011 ranged between 0.6% and 1.2%, indicating a slowing of the population growth in these four regions. It is expected that the overall growth rate in these four regions will continue to decrease into the future.
7.2.2 Urban Population and Growth Rates
A summary of the urban population figures and growth rates four Regions are shown in Table 7.3.
Table 7.3: Summary of Urban Population and Growth in the Ohangwena, Omusati, Oshana and Oshikoto Regions (NSA, 2012)
Urban Population per Region Category Total Ohangwena Omusati Oshana Oshikoto 2001 1% 1% 31% 9% Distribution 2011 10.1% 5.7% 45.2% 13.0% 19% 2001 2,284 2,288 50,194 14,491 69,257 Population 2011 24,790 13,860 79,857 23,656 142,164 % increase 985% 506% 59% 63% 105% Growth Growth rate1 26.9% 19.7% 4.8% 5.0% 7.5%
1. Annualised growth rate
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The portion of the urbanised population has shown a significant increase in the four regions, most notably in the Ohangwena Region, where the urban population increased more than tenfold. Overall, the total urban population in the four regions more than doubled from 2001 to 2011. One of the reasons for this apparently high increase in the urban population is the fact that a number of urban centres were not so classified with the 2001 Census, but were classified as “urban” with the 2011 Census, specifically Helao Nafidi, Oshikuku, Okahao, Omuthiya and Ruacana (refer to Table 3.2).
The 2001 to 2011 urban growth rates vary greatly between the regions, with the Ohangwena Region showing a 26.9% growth rate from 2001 to 2011, whereas the Oshana Region showed a growth rate of 4.75%. Overall, the growth rate in the urban population for all four Regions was 7.5%. Although the rate of urbanisation in the Ohangwena and Omusati Regions, with approximately 2,300 urban dwellers in each, was much lower than in the Oshana and Oshikoto Regions in 2001, the sustainability of these high urban growth rates is uncertain.
Finally, it must be mentioned that due to changes to the enumeration areas between the 2001 and 2011 Census, some urban areas were modified from those used for the 2009 Cuvelai BWMP. For example, the town of Oshigambo had a population of 583 in 2008, based on the 2001 Census (LCE, 2009), whereas the 2011 Census GIS Database results yielded a population of 457, which is unlikely given the overall urban expansion in the Cuvelai area. This complicates efforts to compare the results between the 2001 and 2011 Census, especially on a town level. However, the purpose of this Study was not to focus on town level demands, but rather on the larger-scale demands.
7.2.3 Rural Population and Growth Rates
A summary of the rural population figures and growth rates four Regions is shown in Table 7.4.
Table 7.4: Summary of Rural Population and Growth in the Ohangwena, Omusati, Oshana and Oshikoto Regions (NSA, 2012)
Rural Population per Region Category Total Ohangwena Omusati Oshana Oshikoto 2001 99% 99% 69% 91% Distribution 2011 90% 94% 55% 87% 2001 226,100 226,554 111,722 146,516 710,892 Population 2011 220,656 229,306 96,817 158,317 705,095 % increase -2.41% 1.21% -13.34% 8.05% -0.82% Growth Growth rate1 -0.24% 0.12% -1.42% 0.78% -0.08% 1. Annualised growth rate
The rural population has shown a decrease in two of the four regions (Ohangwena and Oshana), with growth rates in the Omusati and Oshikoto Regions well below those of the urban population (Table 7.3). This is consistent with the growing urban population discussed in the previous section, and therefore the rural-urban migration expected in developing countries.
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Overall, the total rural population in the four regions has decreased by 0.82% between 2001 and 2011.
The 2001 to 2011 growth rates in the rural population vary between the four regions, but ultimately reflect a decreasing or at least stabilising trend. Overall, the annualised growth rate in the rural population for all four regions was -0.08%.
7.2.4 Selected Population Growth Rates for the Cuvelai Area
For the purposes of this Study, variable growth rates were selected from the current year of 2012/13 to 2049/50. Figure 7.2 illustrates the above determined total growth rates of the four northern regions applied to each population category. When constant growth rates of 7.5% (refer to Table 7.3) and -0.08% (refer to Table 7.4) are applied to the urban and rural population of the four northern regions respectively, from 2011/12 onwards (the date of the census), the combined population reaches nearly 3,000,000. However, when the combined growth rate of 0.83% (refer to Table 7.2) is applied to the total population of the four northern regions from 2011/12 onwards, as indicated by the green line in Figure 7.2, the population just exceeds 1,000,000. Therefore, if the total population growth rate remains constant or decreases up until 2049/50, as is expected (refer to the growth rates in Table 7.2), a high urban growth rate is unsustainable and unrealistic.
Figure 7.2: Constant Growth Rates Applied to Population of the Four Northern Regions
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By all accounts, and based on the most recent census results, selected growth rates for demand analyses should reflect stable or decreasing total population growth in the Cuvelai area and simultaneously reflect the current urbanisation trends, with higher growth in the urban population and lower to no growth in the rural population.
To illustrate this further, three growth rate scenarios were explored, based on population data for the Cuvelai area (refer to Sections 7.4.2 and 7.5.2 for more detail):
1. Constant urban, rural and total growth rates from 2011/12 to 2049/50, as illustrated in Figure 7.3. 2. Two growth rates for the urban and rural population, applied between 2011/12 and 2030/31, and between 2031/32 and 2049/50, and a constant growth rate for the total population, as illustrated in Figure 7.4. 3. Four growth rates for each population category applied over 10-year periods; 2011/12 to 2020/21, 2021/22 to 2030/31, 2031/32 to 2040/41 and 2041/42 to 2049/50. Two growth rates applied between 2011/12 to 2030/31, and 2031/32 to 2049/50 for the total population, in order to reflect a decreasing population growth, as illustrated in Figure 7.5.
Figure 7.3: Growth Rate Illustration Number 1: Constant Growth Rates
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The population projections for constant growth rates as per Figure 7.3 indicate that the individual urban and rural population growth rates applied to their respective population categories overestimate the total population compared with the total population growth rate by more than 300,000 people. When two urban and rural growth rates are applied as per Figure 7.4, the overestimation is greatly reduced. Finally, when the four growth rates are applied as per Figure 7.5, the combined urban and rural populations and the total population show very little difference.
Figure 7.4: Growth Rate Illustration Number 2: Variable Growth Rates
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Figure 7.5: Growth Rate Illustration Number 3: Variable Growth Rates
Based on the above, the growth rates provided in Table 7.5 were selected for each population category per water demand scenario:
Table 7.5: Population Growth Rate Assumptions for the Cuvelai Area
Period / Scenario Low Likely Likely High Likely
Urban Population Growth Rates (% per annum)
2011/12-2021/22 2.00 4.00 4.75
2021/22-2031/32 2.00 3.00 4.00
2031/32-2041/42 1.00 2.00 3.00
2041/42-2049/50 1.00 1.00 2.00
Rural Population Growth Rates (% per annum)
2011/12-2021/22 0.10 0.50 0.50
2021/22-2031/32 0.10 0.10 0.50
2031/32-2041/42 0.05 0.05 0.50
2041/42-2049/50 0.00 0.00 0.50
The high likely scenario assumes higher growth rates in both the urban and rural areas (relative to the other scenarios) to allow for the scenario where decentralisation efforts are intensified, thereby preventing the net emigration of people from the Cuvelai to other areas of the country (for example the Khomas and Erongo Regions), thereby resulting in higher population growth rates in the Cuvelai area.
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7.3 FUTURE DEVELOPMENT CONSIDERATIONS
7.3.1 Known and Unknown Future Developments
The following known developments were included with the estimation of the future water demands:
1. The Ruacana South Rural Water Supply Project, 2. The King Kauluma Rural Water Supply Project, 3. The planned expansion of the Etunda Irrigation Scheme.
Another rural water supply project, the Ondangwa – Omuntele Project is currently (March 2014) in the planning and community consultation phase and is likely to be implemented. However, the project is to supply water to livestock and the project area already falls within the Cuvelai area. Therefore, the impact of this project will be taken into account through the livestock estimates derived in Section 7.5.2.4.
With regard to other developments which may impact in water demands, with the preparation of the Cuvelai BWMP, it was found that Regional Development Plans prepared by the different regions were either outdated and / or of little value. With regard to new projects, the rate of implementation through Regional and Town / Village Councils as well as some Government ministries is known to be low, due to a lack of technical capacity in these Councils, budgetary / financial constraints, limitations regarding fiscal years and other factors, and often several years elapse before proposed developments are completed.
It is therefore expected that development in these regions will not proceed at extraordinarily high rates, Vision 2030 notwithstanding, and rather that they will proceed in accordance with historic trends. The main argument for this assumption is the fact that Government ministries, Regional and Town / Village Councils have a limited annual budget, which situation is naturally a constricting factor in the development of public-funded projects.
7.3.2 Ruacana South Rural Water Supply Project The Ruacana South Water Supply Project entails investigating the possibility of supplying water to two areas which lie in both the Omusati and Kunene Regions. One of the areas, Area 1, lies within the Study Area, whilst Area 2 covers a 10 km wide area along the Ruacana – Kamanjab and Omakange – Opuwo roads to Opuwo, as shown in the purple-lined area in Figure 7.6.
It is currently expected that Area 1, which falls within Water Supply Zone 2 (refer to Figure 7.1), will be supplied with piped water via the existing supply infrastructure and therefore via abstraction at Calueque.
All users in Area 2 are rural-based. At the time of writing (March 2014), it remains uncertain whether this area will be supplied by groundwater water in the area via boreholes or by piped water via the existing pipeline network and therefore from abstraction at Calueque. The completion date of the project is currently estimated to be 2015/16.
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Figure 7.6: Supply Area 2 for the Ruacana South Rural Water Supply Project
Given the supply uncertainties, all users in the area have been incorporated into the water demand projections under the high likely scenario from the year 2017/18 onwards (refer to Section 7.5).
7.3.3 King Kaluma Rural Water Supply Project The King Kaluma Rural Water Supply Project, entails investigating the possibility of supplying water to the King Kaluma area, shown in Figure 7.7. All potential users are rural-based. The current completion date of the project is estimated to be 2015/16.
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Figure 7.7: King Kauluma Rural Water Supply Project
Users in the area have been incorporated into the water demand projections under both the likely and high likely scenarios from the year 2017/18 onwards (refer to Section 7.5).
7.3.4 Expansion of the Etunda Irrigation Area On the basis of consultations with the Division Engineering Extension Services in the Department of Agriculture in the MAWF, it has been established that the existing irrigated area of 900 ha at the Etunda Scheme will grow by an additional 300 ha, although no definite time frame was provided for when this is expected to occur. The additional 300 ha has been incorporated into the water demand projections under both the likely and high likely scenarios for the year 2017/18.
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7.4 ESTIMATION OF THE URBAN WATER DEMANDS
7.4.1 Defined Urban Areas
Urban areas were divided into the eight Water Supply Zones, based mainly on the definitions of and the existing urban areas used previously (LCE, 2009). The urban areas contained in each zone and the corresponding populations based on the 2011 Census GIS database are listed in Table 7.6.
Table 7.6: 2011 Population per Urban Area in the Cuvelai Area (2011 Census)
Water Supply Zone Town Population
Olushandja 670
2 Oshifo 1,698
Ruacana 545
3 Outapi 6,215
Okahao 1,540
4 Onesi 294
Tsandi 825
Okalongo 1,018
Omungwelume 701 5 Ongongo 198
Oshikuku 2,342
Eheke 1,245
6 Ongwediva 18,368
Oshakati 34,642
Eenhana 4,898
Helao-Nafidi 18,788
Oshikango 1,751
Ohangwena 4,174
Ongenga 454
7 Endola 807
Iindangungu 406
Odibo 248
Onambutu 842
Ondobe 1,835
Ongha 1,109
Ondangwa 20,021
Omuthiya 3,753
Onayena 169 8 Onethindi 4,520
Oniipa 2,617
Oshigambo 457
Total 137,150
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7.4.2 Population and Institutional Areas by Water Supply Zone
The area values (floor areas) of institutions, which included hospitals, schools, businesses, industrial areas were used from the 2009 Cuvelai BWMP and adapted from 2007/08 to the current 2012/13 with the likely scenario urban growth rate of 4%, as listed in Table 7.7. This derivation is based on the assumption that the provision of institutional services (schools, clinics / hospitals, police stations, prisons, town and regional offices) is based on a relatively constant percentage of the population. Three institutional area values not incorporated into 2009 Cuvelai BWMP, namely Oshakati, Ondangwa and Omuthiya, were added to the total zonal institutional areas in this Report. Their exclusion from the 2009 Cuvelai BWMP was due to the lack of accurate and up to date information at the time (p 5-10 LCE, 2009). The current (2012/13) zonal urban population and institutional areas adjusted are shown in Table 7.7.
Table 7.7: Estimated Current (2012/13) Zonal Population and Institutional Area Values
Water Urban Population Institutional Area (m2)
Supply Zone 2011/12 2012/13 2007/08 2012/13
2 2,913 3,030 7,280 8,181
3 6,215 6,464 22,100 25,854
4 2,659 2,765 19,850 23,222
5 4,259 4,429 25,400 29,714
18,440 21,572
6 54,255 56,425 Oshakati1 450,000
Zone 6 total 471,572
7 35,312 36,724 87,000 101,778
27,950 32,698
Ondangwa1 450,000 8 31,537 32,798 Omuthiya1 70,000 Zone 8 total 552,698
Total 137,150 142,636 208,020 1,213,018
1. Institutional values for Oshakati, Ondangwa and Omuthiya were not determined for the 2009 Cuvelai BWMP.
7.4.3 Income Distribution Factors
The income distribution was kept the same for the low likely and likely scenarios, whereas a higher income distribution was assumed for the high likely scenario, as shown in Table 7.8.
Table 7.8: Assumed Income Distribution per Demand Scenario
Income Portion of Population per Scenario (%) Distribution Low Likely Likely High Likely Very Low 20 20 10 Low 40 40 50 Medium 40 40 30 High 0 0 10
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It must be noted that the high likely income distribution values were introduced from 2020/21 onwards (refer to Figure 7.8).
7.4.4 Water Demand Norms
Water demand norms were based on the values used previously (p 5-9; LCE 2009) and kept constant over each demand scenario, as shown in Table 7.9.
Table 7.9: Assumed Urban Water Demand Norms per Demand Scenario
Water Demand Norms Per Scenario Water Demand Norms Unit Low Likely Likely High Likely Very Low ℓ/c/d 25 25 25 Low ℓ/c/d 55 55 55 Medium ℓ/c/d 80 80 80 High ℓ/c/d 130 130 130 Institutional and Commercial ℓ/m2/d 5 5 5
7.4.5 Current Urban Water Demand Estimation
The current theoretical water demand for the year 2012/13 was estimated using the population and institutional area values determined in Table 7.7 with the income distribution factors in Table 7.8 and water demand norms provided in Table 7.9 applied. The resulting demand values are shown in Table 7.10.
Zones 6-8 clearly have the highest demands compared with the other zones, due to their larger urban population sizes. The total urban water demand for the Cuvelai area was estimated at 14,723 m3/d. The current theoretical demand value is approximately 12% lower than the 2012/13 consumption (sales) value of 16,742 m3/d (refer to Table 6.3). The underestimation could be attributed to increased consumption rates caused by billing inefficiency, the accuracy of the sales data and / or the underlying methodology used to estimate the theoretical demands.
7.4.6 Adopted Urban Water Demand for 2012/13 The adopted urban water demand value used to project the future water demand values was selected as the 14,723 m3/d current theoretical demand value determined above, as it is assumed that the historical consumption values are higher than they should be, and can be reduced with the introduction of Water Demand Management (WDM) measures such as rising block tariffs and increased billing efficiency, which are relatively easily implemented in urban areas.
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Table 7.10: Estimated Current (2012/13) Urban Water Demands for the Cuvelai Area
Population Income Distribution Income-Based Domestic Demand (m3/d) Institutional Areas Total Water Zone Demand Demand Very Low Low Medium Total Very Low Low Medium Total Area (m2) (m3/d) (m3/d) 2 606 1,212 1,212 3,030 15 67 97 179 8,508 43 221 3 1,293 2,585 2,585 6,464 32 142 207 381 26,888 134 516 4 553 1,106 1,106 2,765 14 61 88 163 24,151 121 284 5 886 1,772 1,772 4,429 22 97 142 261 30,903 155 416 6 11,285 22,570 22,570 56,425 282 1,241 1,806 3,329 490,435 2,452 5,781 7 7,345 14,690 14,690 36,724 184 808 1,175 2,167 105,849 529 2,696 8 6,560 13,119 13,119 32,798 164 722 1,050 1,935 574,805 2,874 4,809 Total 28,527 57,054 57,054 142,636 713 3,138 4,564 8,416 1,261,,539 6,308 14,723
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7.4.7 Projected Future Urban Water Demands for the Cuvelai Area
Projected future water demands, based on the variable growth rates (Table 7.5); the factors and norms discussed (Tables 7.8 and 7.9) and the adopted theoretical demand provided in Section 7.4.6, were calculated for each demand scenario up to the year 2049/50, as shown in Table 7.11.
Table 7.11: Future Urban Water Demands for 2049/50 per Demand Scenario
Water Demand (m3/d) Per Scenario Zone Low Likely Likely High Likely 2 382 543 846 3 890 1,265 1,956 4 490 696 1,055
5 718 1,020 1,555
6 9,975 14,176 21,479
7 4,652 6,611 10,303
8 8,298 11,792 17,477
Total 25,405 36,102 54,671
The water demands for each scenario from 2012/13 to 2049/50, as determined above, the historical consumption values from 1997/98 to 2012/13 and the theoretical water demand values of the 2009 Cuvelai BWMP are shown in Figure 7.8 for comparative purposes (note that the values were converted to Mm3/a).
Figure 7.8: Urban Sales and Water Demand Projections for the Cuvelai Area
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From Figure 7.8 it is evident that the theoretically determined demands compare better with the histroric consumption (sales) values than those of the 2009 Cuvelai BWMP, most likely as a result of the lower than expected urban population estimates used between 2001 and 2007/08 in the 2009 Cuvelai BWMP (before the 2011 Census was conducted). The effect the variable growth rates used for the theoretical water demands are also evident when compared with the projections of the 2009 Cuvelai BWMP. It is also evident that urban water consumption (sales) is showing an increasing trend, which is consistent with the growing theoretical demands for all three scenarios.
7.5 ESTIMATION OF THE RURAL WATER DEMANDS
The theoretical rural water demands were determined by taking population figures for the domestic, school and clinic population, and livestock numbers, and multiplying these by the appropriate demand norm values.
7.5.1 Defined Rural Areas
Defined rural areas, based on the Water Supply Zones, also used the additional 7.5 km extension “buffer service areas” for the purposes of estimating livestock demands, as done previously (LCE 2009) and are shown in Table 7.12. The size of the rural areas, with the added buffer areas, was determined by subtracting the urban enumeration areas from the total Cuvelai area, determined from the GIS data of the 2011 Census. It was assumed that the extent of the urban and rural areas would have remained constant from 2011/12 (the 2001 Census) to the current year of 2012/13.
Table 7.12: Rural Area Size According to the 2011 Census GIS Data
Area (ha) Zone Total Urban1 Rural
2 141,495 3,667 137,828 3 498,270 2,773 495,497
4 99,007 1,536 97,470
5 269,907 2,926 266,981
6 245,765 11,652 234,113
7 475,739 21,815 453,924
8 861,549 20,723 840,826
Total 2,591,731 65,092 2,526,639
1. Note that the urban area used is the extent of the enumeration area as obtained from the GIS data of the 2011 Census.
The currently unserved areas of Epinga (29,243 ha including the “buffer service area”) in Zone 7 and Onkumbula (98,436 ha including the “buffer service area”) in Zone 8 have been included in the determination of the rural areas and hence in the rural water demand estimation, on the assumption that these areas will be served with water sooner or later.
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7.5.2 Rural Population and Livestock Numbers
7.5.2.1 Domestic Rural Population The domestic rural population for 2011/12 was determined by subtracting the number of urban dwellers (Table 7.7) from the total population numbers in the Cuvelai area, based on the GIS data of the 2011 Census. To estimate the population of the Cuvelai area for the current, 2012/13 year, the 2011/12 rural population figures were increased with a 0.5% growth rate, which value corresponds with the likely scenario growth rate assumed for the future (Table 7.5). The rural population per Water Supply Zone in the Cuvelai area thus determined is listed in Table 7.13.
Table 7.13: Estimated Current (2012/13) Domestic Rural Population in the Cuvelai Area
Population for 2011/12 Rural
Zone Population Total Urban Rural for 2012/13 2 32,953 2,913 30,040 30,190 3 86,850 6,215 80,635 81,038 4 37,306 2,659 34,647 34,820 5 120,204 4,259 115,945 116,525 6 87,857 54,255 33,602 33,770 71 213,504 35,312 178,192 179,083 82 167,406 31,537 135,869 136,548 Total 746,080 137,150 608,930 611,975
1. Including the Onkumbula service area, 2. Including the Epinga service area.
7.5.2.2 School Population Figures The number of day scholars derived for the 2009 BWMP, for a base year of 2007/08, were determined from a GIS point file provided by John Mendelsohn (LCE, 2009). To estimate the current (2012/13) school population, these 2007/08 figures were increased with a growth rate of 0.5% per annum, which value corresponds with the likely scenario growth rate assumed for the future (Table 7.5). In so doing, it was assumed that the MoE will build schools and employ teachers at a sufficient rate to accommodate the growth in the number of pupils.
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Table 7.14: Estimated Current (2012/13) Number of Scholars for the Cuvelai Area
Number of
Zone Scholars
2007/08 2012/13
2 10,989 11,266
3 12,591 12,909
4 33,325 34,166 5 49,579 50,831 6 26,969 27,650 7 79,578 81,587 8 59,498 61,000 Total 272,529 279,411
7.5.2.3 Clinic Out Patients Under the 2009 BWMP, clinic out patient figures were derived for 2001/02 based on a MoHSS publication and an Environmental Profiles Project for that year. The 2007/08 projections for the base year of that study were then derived by increasing the 2001/02 values (LCE, 2009). Under this Study, these 2007/08 values were increased with a growth rate of 0.5% per annum to derive the current, 2012/13 figures, as done for the rural domestic and school population figures (refer above). As previously, this approach is based on the assumption that the capacity of health facilities will increase in line with the growing population.
Table 7.15: Estimated Current (2012/13) Number of Clinic Out Patients for the Cuvelai Area
Number of Clinic Out
Zone Patients
2007/08 2012/13
2 132 135
3 165 169
4 429 440
5 627 643
6 297 304 7 726 744 8 528 541 Total 2,904 2,977
Generally only outpatient-based health services are available in the rural areas, as hospitals are located in the urban areas, where the water demand is included in the “institutional” category or the urban water demands.
7.5.2.4 Livestock Numbers Livestock numbers are based on the carrying capacity of the rural areas at 10 ha/LSU, as done previously (LCE, 2009), and are shown per zone in Table 7.16.
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Table 7.16: Estimated Current Number of Livestock for the Cuvelai Area
Livestock Area Number of Zone (ha) Livestock1
2 137,828 13,783
3 495,497 49,550
4 97,470 9,747 5 266,981 26,698 6 234,113 23,411 71 453,924 45,392 82 840,826 84,083 Total 2,526,639 252,664
1. Equivalent large stock units. 2. Including the Onkumbula service area, 3. Including the Epinga service area.
7.5.3 Water Demand Norms The water demand norms used for schools, clinics and livestock were largely based on the values used previously (LCE, 2009). All scenarios assumed an initial water demand value for the current 2012/13 year of 25 ℓ/c/d, based on the MAWF’s specified demand norm. For the lower likely scenario, this demand norm was assumed to remain constant until the target year of 2049/50, based on a very low conversion to individual off-takes (refer below).
Under the likely and high likely scenarios, it was assumed that unit consumption rates will increase into the future, based on the observed trend away from communal water points towards direct individual off-takes via manifold connections (refer to Section 6.3). It is well established that when people receive connections closer to their place of residence and walking distances for the collection of water are reduced, unit consumption rates increase. For the high likely scenario, the demand norm was assumed to grow to 60 ℓ/c/d at the end of the projection horizon, based on a manifold connection demand figure estimate. For the likely scenario, the demand norm at the projection horizon was assumed to be the average between the low likely and high likely demand norms; i.e. 43 ℓ/c/d, based on an assumed mix of communal and manifold connections. For both the likely and high likely scenarios, the unit demand values were increased from 25 ℓ/c/d in 2012/13 to 43 ℓ/c/d or 60 ℓ/c/d in 2049/50 respectively in a linear pattern.
Table 7.17: Assumed Rural Water Demand Norms per Demand Scenario
Water Demand Norms Per Scenario Water Demand Norms Unit Low Likely Likely High Likely
Domestic Current: 2012/13 ℓ/c/d 25 25 25
water use End: 2049/50 ℓ/c/d 25 43 60
Schools (day scholars only) ℓ/pupil/d 15 15 15
Clinic outpatients ℓ/patient/d 30 30 30
Livestock ℓ/LSU/d 45 45 45
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7.5.4 Current Rural Water Demand Estimation
The current water demand for the year 2012/13 was estimated using the estimated current domestic, school and clinic population / numbers (Tables 7.13 to 7.15) and the livestock numbers (Table 7.16), to which the adopted water demand norms (Table 7.17) were applied. The resulting estimate of the current rural water demand is shown in Table 7.18.
The domestic and livestock water demands of the currently unserved areas of Epinga in Zone 7 and Onkumbula in Zone 8 have been included in the determination of the current rural water demands as a conservative approach, as these areas will be served with water sooner or later, in order to ensure that they are included in the water abstraction requirements from Calueque (refer to Section 7.9). At present however, since these areas are not served by water supply schemes, no demand by schools or clinics has been included, either for the current or future scenarios. In the case of the latter, it is not clear when schemes will be constructed to serve these areas and it is likely that institutional infrastructure, such as schools and clinics, which have a long “lead time” in terms of planning and implementation, will only be constructed much later than the water supply schemes, if at all.
The total current rural demand was calculated at 30,950 m3/d, with the domestic demands as 19,580 m3/d and the livestock demand as 11,370 m3/d, being 63% and 37% of the total respectively.
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Table 7.18: Estimated Current (2012/13) Rural Water Demands for the Cuvelai Area
3 Population / Numbers Population Water Demand (m /d) Livestock Total Rural Zone Livestock Demand Water Demand Domestic School Clinic Domestic School Clinic Total Area (ha) Numbers1 (m3/d) (m3/d)
2 30,190 11,266 135 755 169 4 928 137,828 13,783 620 1,548
3 81,038 12,909 169 2,026 194 5 2,225 495,497 49,550 2,230 4,454
4 34,820 34,166 440 871 512 13 1,396 97,470 9,747 439 1,835
5 116,525 50,831 643 2,913 762 19 3,695 266,981 26,698 1,201 4,896
6 33,770 27,650 304 844 415 9 1,268 234,113 23,411 1,054 2,322
72 179,083 81,587 744 4,477 1,224 22 5,723 453,924 45,392 2,043 7,766
83 136,548 61,000 541 3,414 915 16 4,345 840,826 84,083 3,784 8,129
Total 611,975 279,411 2,977 15,299 4,191 89 19,580 2,526,639 252,664 11,370 30,950
1. Equivalent large stock units. 2. Including the Onkumbula service area, 3. Including the Epinga service area.
The estimated current rural water demand is approximately 1.9 times larger than the corresponding 2012/13 rural consumption (sales) value of 16,125 m3/d (refer to Table 6.3). This large difference can be attributed to the methodology used to calculate the theoretical demands, whereby it is assumed that the entire domestic population and all the livestock effectively use the assigned water demand norm values every day. This is not necessarily the case with livestock in particular, where surface water is widely used for livestock watering, when available, in order for farmers to save on purchasing water via the pipeline network. In the Omusati Region for example, some livestock water points on the rural water supply pipeline schemes are known to be locked by the community once water is available in the iishana, and only opened in the late winter once the iishana have dried up (LCE, 2011). In addition, the domestic water demand, estimated at 25 ℓ/c/d may be generous in instances where people have to walk significant distances to collect water.
Furthermore, the historic consumption in particularly the rural areas of the Cuvelai is believed to be underrepresented by the sales data, given the logistical challenges NamWater faces in reading and invoicing a rapidly growing number of private connections (refer to Section 6.3), which has resulted in some billing inefficiencies (LCE, 2009).
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7.5.5 Adopted Rural Water Demand for 2012/13
Although the estimated rural water demand value is much larger than the corresponding historic consumption (sales) value, the estimated value of 30,950 m3/d, as determined above, was adopted as the current water demand, since it is believed that the historic sales in the rural area are underrepresented.
7.5.6 Projected Future Rural Water Demands
7.5.6.1 Incorporation of Additional Schemes The expected water demands to be supplied by the Ruacana South and King Kaluma rural water supply schemes (refer to Sections 7.3.2 and 7.3.3 respectively), currently in the planning phase, were included in the projected rural water demands as follows:
1. Domestic population figures and the size of the project areas (for the derivation of the livestock numbers) were obtained from the 2011 Census GIS data, 2. Information on the schools was obtained from the GIS point file used for the 2009 Cuvelai BWMP (refer to Section 7.5.2.2): a. In the Ruacana South area, coordinates were provided for four schools, whilst in the King Kaluma area, coordinates were provided for two schools. b. Unfortunately, the number of school going children was not recorded in this data. It was consequently assumed that each school had 150 school going children. 3. Information on clinics was obtained from a 2010 GIS point data file: a. Coordinates for only one clinic were provided for the Ruacana South area, and none for the King Kaluma area. b. It was assumed that the clinic in the Ruacana South area treats thirty out patients per day.
The domestic, school and clinic figures were adjusted to the current, 2012/13 year, using a growth rate of 0.5% per annum as done elsewhere. The estimated water demands for these two schemes are shown in Table 7.19, which values were then incorporated into the projected future water demands based on the expected completion date of 2015/16 (refer above).
Table 7.19: Estimated Current (2012/13) Rural Population and Livestock Information for the Additional Schemes in the Cuvelai Area
Population Livestock Scheme Zone Domestic School Clinic Area (ha) Numbers1
Ruacana South 2 5,556 612 33 225,801 22,580
King Kaluma 8 2,038 306 0 25,402 2,540
1. Equivalent large stock units.
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7.5.6.2 Projected Future Rural Water Demands for the Cuvelai Area The projected future rural water demands were determined for the different scenarios from the current, 2012/13 adopted rural water demand (Section 7.5.5), to which the adopted variable growth rates (Table 7.5) and water demand norms (Table 7.17) were applied. The livestock numbers were however not increased, on the basis that these are based on the grazing capacity of the rangeland, which is not expected to improve over time.
Table 7.20: Future Rural Theoretical Demands for 2049/2050 per Demand Scenario
Water Demand (m3/d) Per Scenario Zone Low Likely Likely High Likely
2 1,570 2,174 4,440
3 4,506 6,121 8,316 4 1,867 2,576 3,583 5 4,982 7,321 10,550 6 2,351 3,035 4,000 7 7,899 11,494 16,464 8 8,230 10,970 15,025 Total 31,405 43,692 62,380
The differences between the scenario values is attributed to the increasing demand norms applied to the likely and high likely scenarios (Table 7.17), as well as the divergent growth rates used for the different scenarios (Table 7.5).
The water demands for each scenario from 2012/13 to 2049/50, as determined above, the historical consumption values from 1997/98 to 2012/13 and the theoretical water demand values of the 2009 Cuvelai BWMP are shown in Figure 7.9 for comparative purposes (note that the values were converted to Mm3/a).
As noted in Section 7.5.4, it is clear that the adopted rural water demand value is much higher than the historic consumption (sales) values. Trends in the historic rural consumption values are hard to discern, as the data tends to decrease from 2000/01 to 2009/10 and increases from thereon. Demands for the lower likely scenario remain near-constant given the constant water demand norms and growth rates assumed. The likely scenario shows a near linear increase in demand as a result of the linear increase in domestic demand norms. The high likely scenario shows the most growth as a result of the linear increase in demand norms and an assumed constant population growth rate. The noticeable increase in the demand values of the high likely scenario in 2017/18 are as a result of the introduction of the additional schemes discussed in Section 7.5.6.1.
The previous demand projections, prepared under the 2009 Cuvelai BWMP are generally lower than the demand values of the likely scenario, as a result of the use of the 15 ℓ/c/d demand norm used by NamWater (the BWMP was conducted for NamWater using their design norms and standards), in contrast with the 25 ℓ/c/d applied by the MAWF, as under this Study.
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Figure 7.9: Rural Sales and Water Demand Projections for the Cuvelai Area
7.6 COMBINED URBAN AND RURAL DEMANDS
The urban (Section 7.4) and rural (Section 7.5) water demand projections were combined and compared with the combined urban and rural historic consumption (sales) values (refer to Table 6.3). The previous combined urban and rural water demand projections from the 2009 BWMP were also added and are shown graphically in Figure 7.10.
As a result of the fact that the estimated rural water demands are higher than the historic rural consumption (sales), the combined water demand estimates are higher than the historical consumption values. The values derived under the 2009 Cuvelai BWMP are initially lower than the demand estimates of this Study, but exceed both the low likely and likely scenario values at different points. This is most likely as a result of higher growth rates assumed for the urbanised population under the 2009 Cuvelai BWMP. It must also be noted that the demand horizon for the BWMP only extended to 2029/30 and the values prepared under that study were extended for comparative purposes (as shown in Figure 7.10) and were not initially intended to extend as far as 2049/50.
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Figure 7.10: Combined Sales and Water Demand Projections for the Cuvelai Area
7.7 ESTIMATION OF IRRIGATION DEMANDS
7.7.1 Defined Irrigation Areas
Only two irrigation schemes were considered for the demand estimates, the first being the Etunda Irrigation Scheme (located in Zone 2) and the second being the Ogongo Irrigation Scheme (located in Zone 4). Both of these schemes are also included in the NamWater sales data. The Mahenene Irrigation Scheme was omitted from the theoretical demand estimation due to its irregular consumption values in recent years (refer to Section 6.2.5).
The current irrigation area of the Etunda scheme is 900 ha and according to the Division Engineer: Extension Services in the Department of Agriculture in the MAWF, this will expand by 300 ha in the near future, although no expected time of implementation for this expansion was provided (refer also to Section 7.3.4). The additional 300 ha of irrigated area was therefore incorporated into the likely and high likely scenarios in 2017/18. The extent of the Ogongo Irrigation Scheme was measured using Google Earth and was estimated at approximately 30 ha, with no known prospect of expansion. It is clear that the Ogongo Irrigation Scheme will have a minimal effect on the overall irrigation demand, given its small size and low historic consumption, when compared with the Etunda Irrigation Scheme (refer to Table 6.4).
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7.7.2 Water Demand Norms
A design value of 15,000 m3/ha/a (Liebenberg, 2009) was used to estimate the theoretical demands values for all demand scenarios.
7.7.3 Current Demand Estimation
The estimated irrigation demand for the current 2012/13 year, based on the irrigated areas of the Etunda and Ogongo schemes, is shown in Table 7.21.
Table 7.21: Estimated Current (2012/13) Irrigation Water Demand for the Cuvelai Area
Area Water Demand Scheme (ha) (m3/d)
Etunda 900 36,961
Ogongo 30 1,232
Total 930 38,193
7.7.4 Adopted Irrigation Water Demand
The estimated irrigation demand of 38,193 m3/d is much higher than the 2012/13 irrigation consumption (sales) value of 29,178 m3/d (the total irrigation sales of 10.66 Mm3 as per Table 6.4). This is most likely due to the following factors:
1. The demand norm applied assumes that the full area is evenly and continuously irrigated at the same rate throughout the year, which is not the case in reality, since: a. Crop growth and therefore irrigation demand is largely seasonal, b. Climatic conditions (rainfall, temperatures and evapotranspiration), which have a major impact on irrigation water demand, vary seasonally, and 2. The full 900 ha extent of the Etunda Irrigation Scheme was assumed to be irrigated, whilst it is known that the small-scale farmers sometimes struggle to meet their input costs and therefore do not always plant and therefore irrigate the full extent of their plots.
On the basis that the Department of Agriculture requested that the full 900 ha extent be used for the purposed of determining and planning the irrigation water demands, the estimated demand value of 38,193 m3/d, as in Table 7.21, was adopted.
7.7.5 Projected Future Irrigation Water Demands
As previously indicated, the only change in the expected future irrigation water demand is likely to be the addition of 300 ha at the Etunda Irrigation Scheme, which demand has been included into the likely and high likely scenarios. There is in effect therefore no difference between the likely and high likely scenarios, but the notation is retained in order to be consistent with the methodology applied elsewhere.
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Table 7.22: Future Irrigation Demands for the Cuvelai Area for 2049/50
Irrigable Area Water Demand
Scheme (ha) (m3/d)
Low Likely Likely Low Likely Likely
Etunda 900 1,200 36,961 49,281
Ogongo 30 30 1,232 1,232
Total 930 1,230 38,193 50,513
Note that the values for the high likely scenario are not shown as they are identical to those of the likely scenario.
The projected irrigation water demands for the period 2012/13 to 2049/50, the historic consumption values from 1997/98 to 2012/13 the theoretical water demand values of the 2009 Cuvelai BWMP are shown in Figure 7.11 for comparative purposes.
Figure 7.11: Historical Consumption and Theoretical Demands for Irrigation Use
The small difference between the values derived under 2009 Cuvelai BWMP and those of this Study are as a result of the addition of the Ogongo Irrigation Scheme under this Study.
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7.8 TOTAL CURRENT AND FUTURE DEMANDS OF THE CUVELAI AREA
The combined estimated water demands (urban, rural and irrigation) for each scenario from 2012/13 to 2049/50, as determined above, together with the historic consumption (sales) in the Cuvelai area from 1997/98 to 2049/50 are shown in Figure 7.12.
The estimated water demands of all scenarios are higher than the historic consumption values as a result of the fact that the estimated rural and irrigation water demands are higher than their respective historic consumption values (refer to Sections 7.5.6 and 7.7.5 respectively). The large increase in the projected likely and high likely water demands is as a result of the introduction of additional schemes in the rural areas (refer to Section 7.5.6.1) and the additional irrigation area to be added at the Etunda Irrigation Scheme (refer to Section 7.7.5).
The water demand estimates of the 2009 Cuvelai BWMP are initially lower than the likely scenario demand values up until approximately 2039/40. It must also be noted that the demand horizon for the BWMP only extended to 2029/30 and the values prepared under that study were extended for comparative purposes (as shown in Figure 7.12) and were not initially intended to extend as far as 2049/50.
Figure 7.12: Overall Historical Consumption and Theoretical Demands for the Project
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7.9 TOTAL CURRENT AND FUTURE WATER SUPPLY AND ABSTRACTION REQUIREMENTS FOR THE CUVELAI AREA
7.9.1 Water Supply Requirements 7.9.1.1 Water Demands and Water Supply Requirements The term water demands is used to denote the end-user requirements, which are typically volume-derived, for example 25 ℓ/c/d for rural consumers. Allowance has been made for losses in the bulk transfer and distribution networks, where these losses are expressed as a percentage of the water demands. The rural water demands have been increased with 7.5% and the urban water demands with 15%, as previously (LCE, 2009), to allow for losses and other unaccounted for water. The combination of water demands and losses is termed the supply requirement, which is the required volume of water that needs to enter the distribution network at the point of supply, in order to satisfy the water demands of consumers. The water supply requirement for a given zone is therefore the required output (outflow) from the purification plant serving that particular water supply zone.
7.9.1.2 Overall Current Water Supply Requirements The current (2012/2013) estimated water supply requirements for the Cuvelai area are shown in Table 7.23, with the distribution losses of 15% and 7.5% added to the urban and rural water demands respectively.
Table 7.23: Estimated Current (2012/13) Water Supply Requirements for the Cuvelai Area
Water Supply Water Demands Requirements Type Daily Annual Daily Annual
(m3/d) (Mm3/a) (m3/d) (Mm3/a)
Urban 14,723 5.38 16,932 6.18
Rural 30,950 11.30 33,271 12.15
Sub-Total 45,673 16.68 50,203 18.34
Irrigation 38,193 13.95 38,193 13.95
Total 83,866 30.63 88,396 32.29
Losses are not factored into the irrigation water demand, on account of the following:
1. A generous water demand norm is applied in determining the water demands (refer to Section 7.7.4), 2. The bulk of the irrigation water demand is used at the Etunda Irrigation Scheme, whose abstraction point is relatively “high up in the system”, just south of the Namibia – Angola border. There is therefore much less transfer distance involved in supplying this demand than is the case with piped water which is supplied as far as Omutsegwonime in the south east,
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3. The losses in the transfer of irrigation water, mostly to Etunda, will arise mostly from seepage and evaporation from the canal, which losses are accounted for under the NRW (refer below).
7.9.1.3 Future Urban, Rural and Irrigation Water Supply Requirements The future water supply requirements for the Cuvelai area for 2049/50, for each demand scenario, are indicated in Table 7.244.
Table 7.24: Future (2049/50) Water Supply Requirements in the Cuvelai Area
Daily Water Supply Requirements Annual Water Supply Requirements Type / (m3/d) (Mm3/a) Scenario Low Likely Likely High Likely Low Likely Likely High Likely
Urban 29,215 41,518 62,872 10.67 15.16 22.96
Rural 33,760 46,969 67,058 12.33 17.16 24.49
Sub-Total 62,976 88,486 129,930 23.00 32.32 47.46
Irrigation 38,193 50,513 50,513 13.95 18.45 18.45
Total 101,169 139,000 180,444 36.95 50.77 65.91
7.9.2 Abstraction Requirements at Calueque
The abstraction requirement for the Cuvelai area is the required volume of water that needs to be extracted from the Kunene River at Calueque in order to satisfy the demands, including distribution losses, evaporation losses at Olushandja Dam, illegal off-takes, seepage losses, non-billed water and all other factors contributing to the non-revenue water (NRW).
For this Study, it was assumed that with regard to the proportion of NRW, there will be a similar relationship between the theoretically determined water demands and the required abstraction at Calueque, as there is between the historic consumption (sales) and the historic abstraction (refer to Section 6.4).
It was determined that NRW accounted for between 59.2% and 75.5%, with an average value of 68.7%, of the total abstraction at Calueque (Table 6.6). There was also some indication that the proportion of NRW decreased as consumption (sales) increased (refer to Figure 6.12), although it is of course highly unlikely that there will be zero NRW, no matter how high the demand (there will always be evaporation and seepage losses from the canals and forebays as a minimum). Therefore, the total required abstraction was calculated as a function of the estimated water demands and the assumed NRW proportion, as shown in the following equation:
Total Abstraction = Estimated Water Demand / (1 – NRW Proportion)
The NRW proportion accounts for the seepage, evaporation, illegal off-takes, un-billed consumption and distribution losses entirely.
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The NRW proportions assumed for each scenario are provided in Table 7.23. An initial value of 60% NRW was assumed for all scenarios, based on the 59.2% NRW proportion for 2012/13 (Table 6.6). It was also assumed that with better billing efficiency and the application of water demand management measures, NamWater could effectively lower the proportions of NRW in the future. Therefore, for the low likely scenario, it was assumed that the NRW proportion would decrease to 45%, for the likely scenario to 50% and for the high likely to 58%.
As with the increase in the domestic rural water demands over time (refer to Section 7.5.6.2), a linear relationship (a reduction in this insance) between the NRW portion in the current year of 2012/13 and those in the final year of 2049/50 was assumed for all three scenarios.
Table 7.25: Variable Proportions of Non-Revenue Water for the Different Demand Scenarios
Portion of Non-Revenue Water Projection Horizon per Scenario (%) Low Likely Likely High Likely Beginning: 2012/13 60 60 60 End: 2049/50 45 50 58
7.9.2.1 Current Required Abstraction at Calueque Dam The estimated current (2012/13) abstraction requirements, based on the estimated water demands (Table 7.23) and the proportions of NRW (Table 7.25), are shown for the likely scenario in Table 7.26.
Table 7.26: Estimated Current (2012/13) Abstraction Requirements for the Cuvelai Area at Calueque
Volume Description (Mm3/a)
Water demand 30.63
Non-Revenue Water (60%) 45.95
Total Abstraction at Calueque 76.58
The total estimated abstraction requirement of 76.58 Mm3/a is approximately 30% higher than the corresponding historic abstraction volume of 59.09 Mm3/a for 2012/13, due the estimated rural and irrigation water demands being greater than the equivalent historic consumption values.
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7.9.3 Future Required Abstraction at Calueque Dam
The estimated future (2049/50) abstraction requirements, based on the estimated future water demands (Table 7.24) and the proportions of NRW (Table 7.25) are shown for all three demand scenarios Table 7.27.
Table 7.27: Estimated Future (2049/50) Abstraction Requirements for the Cuvelai Area at Calueque
Volume
Description Mm3/a
Low Likely Likely High Likely
Water demand 34.70 47.59 61.20
Non-Revenue Proportion 45% 50% 58%
Non-Revenue Water 28.39 47.59 84.52
Total Abstraction at Calueque Dam 63.09 95.19 145.72
7.9.4 Summary of the Projected Water Demands and Abstraction Requirements
A summary of the water demands for the Calueque area and the abstraction requirements at Calueque are shown in Figure 7.13. The Historical Abstraction line indicates the historic abstraction volumes at Calueque (refer to Section 6.4.1), whilst the Maximum Abstraction line indicates the maximum allowable abstraction from the Kunene River at Calueque, based on a 6 m3/s abstraction rate pumped over twenty four hours (refer to Section 3.4.1.4). The historic consumption (sales) and the demands shown in Section 7.8 are also included for illustrative purposes.
The estimated required water abstraction at Calueque is higher than the historic values recorded to date for all three scenarios, due to the estimated rural and irrigation water demands being greater than the equivalent historic consumption values.
The decrease in abstraction volumes projected for the low likely demand scenario is due to the low expected growth in demand and the reduction in the proportion of NRW. The stabilisation in the projected abstraction volumes for the likely scenario, from about 2017/18 onwards (a “flat gradient), despite the increasing water demands for this scenario (refer to Figure 7.12), is also due to the assumed reduction in the proportion of NRW. Both of these instances clearly illustrate how WDM measures can reduce the required abstraction at Calueque. The implications of such measures will be hugely beneficial to NamWater in that:
1. Operational costs will be reduced due to lower pumping costs at Calueque, thereby improving NamWater’s financial position, 2. The security of supply to the Cuvelai will be improved, in that the flow in the Kunene is more likely to exceed lower required volumes of abstraction.
Chapter 7: Water Demands in the Cuvelai Area 7-33 THE AUGMENTATION OF WATER SUPPLY TO THE CENTRAL AREA OF NAMIBIA AND THE CUVELAI PART II: THE CUVELAI AREA OF NAMIBIA
Figure 7.13: Historic and Estimated Abstraction Requirements for the Cuvelai Area
It is further noted that under none of the water demand scenarios, does the projected abstraction volume exceed the maximum allowable abstraction limit from the Kunene River, although this does not necessarily imply that the flow rate in the river will in future allow this abstraction rate.
Chapter 7: Water Demands in the Cuvelai Area 7-34