Instituto da Cooperação Portuguesa (Portugal)

Ministério da Energia e Águas de Angola

SOUTHERN AFRICAN DEVELOPMENT COMMUNITY

PLAN FOR THE INTEGRATED UTILIZATION OF THE WATER RESOURCES OF THE HYDROGRAPHIC BASIN OF THE CUNENE RIVER

SYNTHESIS

LNEC – Laboratório Nacional de Engenharia Civil

Page 1/214 LNEC – Proc.605/1/11926 MINISTÉRIO DO EQUIPAMENTO SOCIAL

Laboratório Nacional de Engenharia Civil

DEPARTMENT OF HYDRAULICS

Section for Structural Hydraulics

Proc.605/1/11926

PLAN FOR THE INTEGRATED UTILIZATION OF THE WATER RESOURCES OF THE HYDROGRAPHIC BASIN OF THE CUNENE RIVER

Report 202/01 – NHE

Lisbon, July 2001

A study commissioned by the Portuguese Institute for Cooperation

I&D HYDRAULICS

Page 2/214 LNEC – Proc.605/1/11926

PLAN FOR THE INTEGRATED UTILIZATION OF THE WATER RESOURCES OF THE HYDROGRAPHIC BASIN OF THE CUNENE RIVER

SYNTHESIS

Page 3/214 LNEC – Proc.605/1/11926 PLAN FOR THE INTEGRATED UTILIZATION OF THE WATER RESOURCES OF THE HYDROGRAPHIC BASIN OF THE CUNENE RIVER

INTRODUCTORY NOTE

This report synthesizes a number of documents that have been elaborated for the Portuguese Institute for Cooperation. The main objective of the work was to establish a Plan for the Integrated Utilization of the Water Resources of the Hydrographic Basin of the Cunene River.

As the elaboration of this Plan is a multi-disciplinary task, it was deemed preferable to grant independence of reporting on the work of each team that contributed to the final objective. That is why each report consists of a compilation of volumes.

REPORT I VOLUME 1 – SYNTHESIS (discarded) VOLUME 2 – PRELIMINARY DESCRIPTION OF THE AVAILABILITY OF SURFACE WATER VOLUME 3 – DESCRIPTION AND PRELIMINARY EVALUATION OF THE AVAILABILITY OF UNDERGROUND WATER VOLUME 4 – INVENTORY OF LAND RESOURCES THAT ARE SUITABLE FOR POTENTIAL IRRIGATION VOLUME 5 – DESCRIPTION OF CURRENT ENVIRONMENTAL INDICATORS VOLUME 6 – THE SOCIAL ECOLOGY OF THE BASIN – PRELIMINARY CHARACTERIZATION VOLUME 7 – OVERALL DESCRIPTION OF THE HYDROLOGIC INFRASTRUCTURES

REPORT II VOLUME 1 – SYNTHESIS (discarded) VOLUME 2 – DESCRIPTION OF THE AVAILABILITY OF SURFACE WATER VOLUME 3 – DESCRIPTION AND EVALUATION OF THE AVAILABILITY OF UNDERGROUND WATER VOLUME 4 – EVALUATION OF WATER REQUIREMENTS VOLUME 5 – PROPOSED STRATEGIES FOR THE SUPPLY OF WATER RESSOURCES

REPORT III VOLUME 1 – OPTIMALIZATION AND SIMULATION OF THE HYDRO- ELECTRICAL STRUCTURE OF THE UPPER CUNENE VOLUME 2 – SIMULATION OF THE HYDROGRAPHIC BASIN OF THE CUNENE RIVER

Page 4/214 LNEC – Proc.605/1/11926 The study was carried out in interaction with Angolan technicians. It is hoped that the elements that were included in these documents may provide pertinent contributions for the implementation of the Master Plan for the Cunene River.

July, 2001

The Project Coordinator

João Soromenho Rocha

Page 5/214 LNEC – Proc.605/1/11926 PLAN FOR THE INTEGRATED UTILIZATION OF THE WATER RESOURCES OF THE HYDROGRAPHIC BASIN OF THE CUNENE RIVER

SYNTHESIS

Summary

A series of studies were carried out by a multi-disciplinary team with the objective to elaborate a Plan for the Integrated Utilization of the Water Resources of the Hydrographic Basin of the Cunene River. Beyond its introduction, the synthesis contains an account of prior studies, a description of existing infrastructures, it refers to international agreements, indicates supporting documentation, summarily describes the hydrographic basin, makes an evaluation of the available water resources, of surface and underground water, assesses water requirements and a provides a description of current environmental indicators. In addition, after proposing strategies for the schemes related to water resources, it presents simulations that were carried out and concludes with the definition of the Plan for the Integrated Utilization of the Water Resources of the Hydrographic Basin of the Cunene River.

Page 6/214 LNEC – Proc.605/1/11926 TABLE OF CONTENTS

1. INTRODUCTION ...... 15 2. BACKGROUND ...... 18 2.1 Introduction ...... 18 2.2 Studies by the Mixed Technical Commission (1926) ...... 18 2.3 Studies by the Southern Angola Mission (1946) ...... 19 2.4 Master Plan for a Hydro-electric Scheme for the area upstream from Matala (1962) ...... 23 2.5 Water Supply Scheme for the Area Upstream from Calueque (1966) .27 2.6 International Agreements in respect of the allocation / sharing of the use of water resources from the Cunene River (1926, 1964 and 1969) ..... 31 2.7 Studies and Projects carried out after 1969 ...... 35 3. SUPPORTING DOCUMENTS ...... 38 4. DESCRIPTION OF THE HYDROGRAPHIC BASIN ...... 39 4.1 Location ...... 39 4.2 Topography ...... 39 4.3 Hydrographic morphology, relief and structure ...... 42 4.4 Geology...... 50 4.5 Climate ...... 56 4.6 Pedology ...... 61 4.7 Vegetation cover ...... 64 4.8 Demographics and population ...... 72 5. EVALUATION OF WATER RESOURCES ...... 82 5.1 Surface Water ...... 82 5.1.1 Hydro-meteorological information, rainfall and river capacities...... 82 5.1.2 Compilation and supplementing of missing data ...... 86 5.1.3 Management of artificial drainage systems ...... 90 5.1.4 Water Resources in the Lower Cunene Area ...... 93 5.2 Underground water ...... 106 5.2.1 Description of the hydro-geological systems ...... 106 5.2.2 Evaluation of underground water resources ...... 111 6. PARTIAL EVALUATION OF WATER REQUIREMENTS ...... 115 6.1 Introduction ...... 115 6.2 Water supply to rural areas ...... 116 6.3 Water supply to urban areas ...... 120 6.4 Water supply for cattle ...... 123 6.5 Water supply for irrigation purposes ...... 126

Page 7/214 LNEC – Proc.605/1/11926 6.6 [missing in both index and text] ...... 133 6.7 Water consumption and water restrictions ...... 133 6.8 The flow of water to Namibia ...... 139 7. SIMULATION OF THE SUPPLY OF WATER RESOURCES...... 143 7.1 Introduction ...... 143 7.2 The IRAS simulation model ...... 145 7.2.1 Introduction ...... 145 7.2.2 The simulation process ...... 147 7.2.3 Structure of the system ...... 149 7.2.4 Input data for the system ...... 151 7.2.5 Operating conventions for the system...... 153 7.2.6 The simulation sequence ...... 155 7.2.7 Simulation procedures, methods and hypotheses ...... 158 7.3 Results of simulations ...... 161 7.3.1 Introduction ...... 161 7.3.2 Perimeters and zones ...... 162 7.3.3. Diagrams expressed in terms of time and space ...... 162 7.3.4 Dynamic images of the system in relation to time ...... 163 7.3.5 Presentation of statistics ...... 164 7.3.6 Probability projections ...... 165 7.3.7 Dossier containing unsatisfactory events and tables...... 166 7.4 Definition of the Cunene River System ...... 167 7.4.1 Introduction ...... 167 7.4.2 Definition of the initial system (CuneneA) ...... 168 7.4.3 Strategies for the supply of water resources from the Cunene ...... 172 8. SIMULATIONS OF THE HYDROGRAPHIC BASIN OF THE CUNENE RIVER ...... 173 8.1 Definition of methods ...... 173 8.1.1 Definition of the second Cunene River System (CuneneB0) ...... 173 8.1.2 Definition of the third Cunene River System (CuneneB1) ...... 176 8.1.3 Definition of the other Cunene River Systems (CuneneB2 to CuneneB5) ...... 177 8.2 Entry data for simulation by IRAS ...... 178 8.2.1 Simulation periods ...... 178 8.2.2 Data for the nodal points ...... 185 8.2.3 Data for the arcs ...... 191 8.3 Results of the simulations by IRAS ...... 192 8.4 Analysis of the results of simulations by IRAS ...... 198 8.4.1 Simulation of system – CuneneA ...... 198

Page 8/214 LNEC – Proc.605/1/11926 8.4.2 Simulation of system – CuneneB0 ...... 199 8.4.3 Simulation of system – CuneneB1 ...... 199 8.4.4 Simulation of system – CuneneB2 ...... 200 8.4.5 Simulation of system – CuneneB3 ...... 201 8.4.6 Simulation of system – CuneneB4 ...... 201 8.4.7 Simulation of system – CuneneB5 ...... 202 8.4.8 Simulation of system – CuneneC5...... 202 8.4.9 Simulation of system – CuneneD5...... 203 8.5 Synthesis of the simulations by IRAS...... 204 9. EPILOGUE ...... 207

Page 9/214 LNEC – Proc.605/1/11926 INDEX – TABLES

Table 1 – Population of the municipalities that make up the Basin, by province Table 2 – Areas in the hydrographic basins that drain into the hydrometric seasons Table 3 – Annual water volumes per basin that are required by the year 2020 for the rural areas of the Cunene (hm3/year) Table 4 – Daily water volumes per basin, for the human population in the rural areas of the Cunene (m3/day) Table 5 – Annual water volumes per basin, required by the year 2020 for the urban areas of the Cunene (hm3/year) Table 6 – Daily water supply volumes, per basin, for the human population in the urban areas of the Cunene, by the year 2020 Table 7 – Annual water volumes, per basin, required by the year 2020 for livestock in the rural areas of the Cunene, by the year 2020 (hm3/year) Table 8 – Daily water supply volumes, per basin, for livestock in the rural areas, by the year 2020 (m3/day) Table 9 – Annual water volumes (hm3/year) and flow volumes (m3/s), per basin, required for irrigation purposes in the Cunene River Basin Table 10 – Annual water volumes, per basin, required by the year 2020 for bulk consumers (hm3/year) Table 11 – Daily water volumes, per basin, required by the year 2020 for bulk consumers (x106 m3/day) Table 12 – Hydrometric stations Table 13 – Urban areas to be supplied Table 14 – Dams on the Cunene River Table 15 – Hydrometric stations in the secondary system Table 16 – Urban areas to be supplied in the second system Table 17 – Dams on the Cunene River Table 18 –Irrigation perimeters on the Cunene River Table 19 –Irrigation perimeters requiring supply Table 20 – Consumption in the urban areas of the CuneneA system Table 21 – Consumption in the urban areas of the CuneneB0 system and subsequent systems Table 22 – Consumption for irrigation purposes in the CuneneB0 system

Page 10/214 LNEC – Proc.605/1/11926 Table 23 – Quotas, volumes and surface areas of the Gove Dam Table 24 – Quotas, volumes and surface areas of the Matala Dam Table 25 – Quotas, volumes and surface areas of the Calueque Dam Table 26 – Quotas, volumes and surface areas of the Ruacana Dam Table 27 – Quotas, volumes and surface areas of the Jamba-ia-Oma Dam Table 28 – Quotas, volumes and surface areas of the Jamba-ia-Mina Dam Table 29 – Quotas, volumes and surface areas of the Catembulo Dam Table 30 – Quotas, volumes and surface areas of the Cova do Leão Dam Table 31 – Definition of zones within the dams Table 32 – Evaporation from the four dams (mm) Table 33 – Data for the arcs with electricity production Table 34 – Definition of the limits on consumption in the urban areas of the CuneneA system Table 35 – Consumption in the urban areas for CuneneB0 and subsequent systems Table 36 – Boundaries of the zones within the four dams (m) Table 37 – Consistency of water supply in the Cunene River Basin Table 38 – Flexibility of the water supply in the Cunene River Basin Table 39 – Percentages of water supply and requirement in the Cunene River Basin

Page 11/214 LNEC – Proc.605/1/11926 INDEX – FIGURES

Figure 1 – Comparison of the various general schemes in the Cunene River Basin Figure 2 – Location of the Cunene River Basin Figure 3 – The Cunene River Basin and its hydrographic grid Figure 4 – Longitudinal profile of the Cunene River Figure 5 – Geological Map of the Cunene River Basin Figure 6 – Climatic zones in the Cunene River Basin Figure 7 – Average annual temperature in the Cunene River Basin Figure 8 – Average annual rainfall in the Cunene River Basin Figure 9 – Dominant soil types in the Cunene River Basin Figure 10 – Phytogeographical zones in the Cunene River Basin Figure 11 – Natural pasture resources in the Cunene River Basin Figure 12 – Agro-economic zones in the Cunene River Basin Figure 13 – Contribution, by province, to the total population of the Cunene River Basin Figure 14 – Geographical delimitation of the Cunene River Basin, by municipal areas Figure 15 – Demographic structures of the provinces of Huambo, Huíla and Cunene in the year 1990 Figure 16 – Pluviometric, climatographic and meteorological stations Figure 17 – Hydrometric stations Figure 18 – Diagram of the procedure to supplement the data for each of the hydrometric stations Figure 19 – Comparison of averages and deviation patterns in compiled and historic values Figure 20 – Variation of the weighted averages on the Cunene Basin, as defined at Quiteve Figure 21 – Evolution of precipitation in Huambo Province Figure 22 – Evolution of precipitation in Huíla Province Figure 23 – Synchronization and modulation between the precipitation at Huíla and the discharge at Ruacana Figure 24 – Synchronization and regression between the discharges at Namuculungo and Ruacana. Figure 25 – Annual correlation between the precipitation in Huíla Province and the discharge at Ruacana

Page 12/214 LNEC – Proc.605/1/11926 Figure 26 – Validation of the model as compared to previous estimates for Calueque Figure 27 – Curve of duration of monthly discharge at Ruacana Figure 28 – Annual discharge at Ruacana Figure 29 – Map of the aquifers in the Cunene Basin Figure 30 – Areas for irrigation in the Cunene Basin Figure 31 – Initial schema of the Cunene River for purposes of simulation by IRAS Figure 32 – Second system of the Cunene River for purposes of simulation by IRAS Figure 33 – Third system of the Cunene River for purposes of simulation by IRAS Figure 34 – System CuneneB2 for purposes of simulation by IRAS Figure 35 – System CuneneB3 for purposes of simulation by IRAS Figure 36 – System CuneneB4 for purposes of simulation by IRAS Figure 37 – System CuneneB5 for purposes of simulation by IRAS Figure 38 – Example of a series of graphs showing the simulation results Figure 39 – Example of probability projection of the simulation results

Page 13/214 LNEC – Proc.605/1/11926 INDEX – APPENDICES

Appendix 1 – Agreement between the Government of Portugal and the Government of the Republic of South Africa on the 1st Phase of the Supply of Water Resources from the Cunene Basin Appendix 2 – Documentary references Appendix 3 – Flowfiles

Page 14/214 LNEC – Proc.605/1/11926 PLAN FOR THE INTEGRATED UTILIZATION OF THE WATER RESOURCES OF THE HYDROGRAPHIC BASIN OF THE CUNENE RIVER

SYNTHESIS

1. INTRODUCTION

The concept of the Plan for the utilization of water resources of a hydrographic river basin can have a variety of meanings, and may need to be defined in different ways, by various groups or individuals. Such diversity is mainly caused by the many problems that exist in that particular basin. The problems encountered are a direct result of the physical characteristics of that basin and the people who make use of the water resources.

Amongst other possible diversities, the Plan might be on a national, regional or local scale; it might aim at long-term or short-term objectives; it might deal with a humid area or with one that is either arid or semi-arid; it can just be limited to surface water or to underground water or deal with both at the same time; it might involve industrialized or developing countries; it might look at all basins in one country or at cross-border basins, etc.

Any tentative to extrapolate methods, most significant parameters, strategies and related economic concepts might lead - from one basin to the next - to plans that are lopsided in respect of reality and, as a consequence, to difficulties with their implementation at a later stage, if the specifics that are inherent to the hydrographic basin under consideration are not taken into account.

This tentative to extrapolate a plan shall obviously also be somewhat lacking when compared to reality, in as much as there were major differences between the basins in question, the one that served as a model and the one that was used for the attempt at extrapolation.

Page 15/214 LNEC – Proc.605/1/11926 This is of particular importance when it is a question of establishing a Plan for the utilization of water resources in developing countries. In this situation one needs to give particular attention to three main objectives.

One is the simple enhancement of the quality of life and the well-being of the population, providing goods and services, with training and educational programs. A secure water supply has to be assured, an improvement of public health, and, wherever necessary – water for irrigation purposes.

Another main objective concerns the improvement of the quality of life and the social well-being through a change of life-style. Examples that could be cited are to conduct nomadic people to a sedentary way-of-life, to change agricultural methods and to establish new residential hubs.

A third aim is – albeit indirectly – associated with the fact that investments for the construction of the necessary infrastructures for the conveying of water resources need to be made available. Such investments will generate an increase in employment and stimulate the economy, and will boost the rate of economic development.

Taking the above into account, the Plan for the Integrated Utilization of the Water Resources of the Hydrographic Basin of the Cunene River has taken the methodology into consideration that was envisaged in the Initial Report dated October 1989, but with subsequent adjustments both as regards the specific objectives that have resulted from detailed quantification that could only be obtained during the work as such, and as far as the evolution of the internationally acceptable concepts are concerned on the subject of planning for water resources, and that have been developed throughout the recent years.

As a result, the initiative to compile a Plan was initiated in June 1989, within the framework of the SADCC – Southern African Development Coordination Conference – which was sponsored by the Portuguese Government through its Secretary of State charged with Foreign Affairs and Cooperation, and [this initiative] was part of “Project Activity 3.0.5”. After some time, it was recognized that it was also very important to provide support to Angola in its negotiations on sharing water resources with Namibia.

Page 16/214 LNEC – Proc.605/1/11926 On the other hand, and due to the civil conflict that caused the displacement of large parts of the population that it was difficult to keep track of, and the fluctuations in the occupation of the Basin would result in increased difficulties at all levels to make [any kind of] forecast as regards the water requirements.

There are several reasons, in particular the advantage in temporarily linking the compilation of the Plan with the Feasibility Study for the supply of Epupa, the difficulty to travel within the Cunene River Basin that drastically curbed field-work, and because of the initial intention to concentrate the works within just over a year – all this resulted in the acknowledgment that the full development of the Plan would have to include subsequent and comprehensive investigation of certain topics. However, the essence would have been achieved with the present Plan.

In accordance with the Organization and Programming of Studies, the 1st phase of the work included the elements in respect of: i) compilation of additional hydro-meteorological data; ii) summary description of the hydrographic basin; iii) evaluation of the available water; iv) evaluation of water requirements; v) preliminary environmental description; vi) preliminary description of existing infrastructures.

The other elements were presented in the subsequent phases, like for example the formulation of strategies for the supply of water resources, the analysis and selection thereof. The reports that were compiled consisted of several volumes, whereby each volume – in addition to the present synthesis – concentrated on subjects of major significance for the work that was carried out by each team.

Page 17/214 LNEC – Proc.605/1/11926 2. BACKGROUND

2.1 Introduction

At the conclusion of the elaboration of the study which led to the compilation of the present Plan, the LNEC (Laboratório Nacional de Engenharia Civil) published a book in its „Eyewitnesses‟ (Testemunhos) series, with the Title “The contribution of the Cunene River. Its importance on an international level and for Southern Angola”, written by Eng. Rui Sanches. Among the manifold technical and political tasks of this author, he was among those responsible for the Overall Plan for a Hydro-electrical Scheme in the Cunene Basin, upstream from Matala and for the Project for a Hydro-electrical Scheme at Gove, also on the Cunene River.

Due to his intense intervention in the area of the Cunene River, his reports are very abundant and detailed. It is for this reason that the perusal of this work is recommended in order to complement the information that is set out in this chapter. As a matter of fact, his publication contains a historical analysis of the Cunene River that remounts to the 17th Century. In the present Synthesis which was compiled before the publishing of the above-mentioned book, we only touch on the technical references that relate to the 20th Century.

2.2 Studies by the Mixed Technical Commission (1926)

The earliest references with this date refer to the Accords signed on 1 and 22 June 1926 (in Cape Town), that were first published in the Government Gazette – 1st Series / January 8, 1927. The second Accord established the border [state] line.

After the signature of the agreements between Portugal and the South African Union, the Official Bulletin of the General Colonial Agency – in the person of Eng. Carlos Roma Machado – published three articles that referred to the water supply of the Cunene. These were respectively: “The Cuamato-Cuanhama Region – the Granary of the High Plateau. Its Indigenous Issue and its Correlation with the Southern Angolan Border. Re-population and Culture” (Nr.19, January 1927) and: “Study Mission and the Origins of the Waters of the Cunene River” (Nr. 42, December 1928).

Page 18/214 LNEC – Proc.605/1/11926 These articles refer to the measurement of minimum flow volumes in times of drought, in the years 1914, 1916 and 1920, which were measured as 3m3/s and 7m3/s respectively at the two last dates. They also proposed an outline for the hydro-electrical supply to Naulila, downstream from Ruacana.

When the state borders were delimited, the lack of water resources in Southwest Africa was taken into account, and Portugal committed itself at the time to provide [Southwest Africa] with water for humanitarian purposes and to study the possibility of deviating the river, by means of gravity, and by building a dam at Calueque. The Accord dated 1 June envisaged “the regulation of the utilization of the water of the Cunene River, the generation of electrical energy, inundation and irrigation in the territory under the Mandate for Southwest Africa”. This Accord allowed the construction and the exploitation of specific works in the Cunene, on Angolan soil. The electricity generation that was mentioned in the Accord was included in localized and [well-] defined mechanisms, but the same did not happen regarding the collection and transport of water towards Southwest, [a subject] that remained pending for subsequent studies.

A Mixed Technical Commission was created through the same Accord, with the task to study and gather elements on water management of the Cunene River, at the southern border of Angola, and to analyze the potentialities of the region. A scarcity of data and great difficulties impeding the carrying out of studies were the salient conclusions of the work of the Mixed Technical Commission (which met in 1927). A disagreement ensued about the height of the dam that was to be constructed at Calueque, and regarding the enormous areas of Angolan soil that would be inundated and which would lead to large-scale inundation [sic]. In the end it was determined that the flow over the Ruacana Falls would never provide sufficient and permanent regimen without considerable expenditure for dam walls, and that such a study would entail compiling a new Convention between the two countries.

2.3 Studies by the Southern Angola Mission (1946)

Decree Nr. 32840 was published on 9 June 1943, in which the policy was established that “the study for the supply of hydro-agriculture would be of major interest for progress and prosperity in Angola”. Subsequent to this policy the Autonomous Hydro-

Page 19/214 LNEC – Proc.605/1/11926 agricultural Brigade of Angola was founded, with the mission statement “that its work would be initiated in the region of Humpata, more specifically in the Neves Basin and [on the] the Tchimpumpunhime River”. In that region one would find the large nucleus of colonization of Chibia, founded in 1885, at an altitude of more than 1500m and with a continental-type climate. In the year 1944, there was a problem of a socio-economic nature that required an urgent solution.

At that time, the Palanca Dam was planned to provide for an area of 1600 hectares, over portions of Chibia and Mupaca, on the High Plateau of Huíla. This dam had a NPA with a level of 1870m; it was conceived for a dam wall with a height of 16m, and had a volume of 14,3hm3, which could be increased until 22,3hm3 at a NMC [level] of 1871,5m, for a tributary basin of 323km2.

During the drought in 1946 a “Mission to Southern Angola” was carried out, under the leadership of Eng. Trigo de Morais, with the aim of inspecting the work by the Autonomous Brigade and in order to promote, without further delay, the conclusion of the studies on the best technical, economic and social solution. This resulted in the possibility to increase the area under irrigation by 2335 hectares in the High Plateau of Huíla, by simply adopting an alternative for the discharge of rainwater.

The report with the title “Mission to Southern Angola” encompasses existing studies on the hydrographic basin to the south of Matala, which had been compiled either by Portugal or by South Africa, and presents a scheme for supplying hydro- electricity, hydro-agriculture and cattle farming (Figure 1). That Mission took place as part of the concept of the Autonomous Squadron within the Hydro-agricultural Works of the Ministry for Public Works and Communication.

The scheme that was compiled by the [above-mentioned] Mission includes thirteen supplies and an offshoot towards Southwest Africa, upstream from Calueque. Six hydro-electric supplies were proposed, with a total possible electricity production of 309GWh, and of which four were situated on the Cunene River (Matala, Iacavala, Ruacana and Santa Maria), and two on the Caculavar River, a right-bank tributary, at N‟Pombo and Cahama; a cattle farm with 420 000 hectares in the Mulola Mucope area, between Matala and the junction with the Cului River; and seven areas to benefit from

Page 20/214 LNEC – Proc.605/1/11926 hydro-agriculture (Capelongo, Quiteve-Humbe, Quihita, Cahama-Humbe, Dongoena, Calueque and Chitado) with a total surface of 42 500 hectares, from the Capelongo (immediately downstream from Matala), to the central Cunene River scheme and linked to the supply from the Caculavar. It also contained an appendix with the analysis of the iron ore in Mount Mucalécanamanga (Chitado).

The only document that is available is Section 3, containing graphs concerning o Project Nr.1 – The Hydro-electric Works on the Cunene, at Matala, with a dam that will overflow at a level of 1304m, which corresponds to a height of approximately 7m, and restitution to a level of 1285m, originating from a height of around 19m; o Project Nr. 3 – Hydro-agricultural improvement of the Mulola Mucope, including the pump station at Mulondo, with around 30m difference in height, measured from an approximate river level of 1250m in the Cunene River; o Project Nr. 5 – Hydro-agricultural improvement and Hydro-electrical scheme at Quihita (N‟Pombo), on the Caculavar River, with an NPA at 1402m, and a dam with a maximum height of 20m; o Project Nr. 6 – Hydro-agricultural improvement in the Caculavar Valley at Humbe, with three alternative levels of NPA, with respective dam levels of 1187m, 1190m and 1194m and dams with respective maximum heights of 17, 20 and 23m; and, finally, o Project Nr.11 – Hydro-electrical scheme at Ruacana, with a dam with a level of 844m, with a maximum height of 6m, and restitution levels of 725m, which corresponds to a difference in altitude of around 119m.

Of these projects the ones at Matala and Ruacana showed greater detail, with the former already comprising designs for the structures whilst the others were merely outlined.

The Project for the Hydro-electrical Improvement of the Cunene River at Matala was presented during 1951, by the Ministry for Overseas Affairs, Province of Angola. The wall height was set at 1306m, with a corresponding downstream level of the falls at 1284m, and to a geometrical drop of 22m. It was ascertained from the hydrological study that was carried out by the “Mission to Southern Angola” during 1946 that one could

Page 21/214 LNEC – Proc.605/1/11926 allow – rather conservatively – for the following continuous volumes: 65m3/s during 8 months and 23,3m3/s during 4 months. Based on the premise that this scheme at Matala would be the first echelon of the Cunene River, when regularizations could be made at its upper levels, and, in view of the type of exploitation that had been chosen and that would not allow future expansion, it was judged to be sensible to immediately plan for generating equipment that was based of future volumes of 65m3/s. If one took a charge factor of 40% into account, a peak volume of 162,5m3/s was obtained for an exploitable volume of 19,80m. The forecasted annual production was 92 GWh. This electricity was intended for the supply of the farming, cattle-breeding and industrial area of central Cunene (Matala-Capelongo-Muilongo) and the city of Sá da Bandeira (now Lubango), that were served by high voltage power lines with a capacity of 60 KV, with lengths of respectively 110 and 180km.

The scheme at Matala includes a dam-bridge combination, metal sluice-gates and a connecting dam to the central power plant, a water inlet, a station, an outlet, a command post, a transformer and accesses, and the electro-mechanical equipment, electrical appliances and overhead power lines.

The dam/bridge over the Cunene River, just upstream from the Matala falls, [would be executed] with reinforced concrete, was planned with a total length between the axes of the supports in the abutments of 929m, which corresponded to 45 spans of 29m and two additional ones, one at each side, of 14,5m. This bridge would provide a link to the road between Capelongo and Vila da Ponte, and to the railway line from Moçamedes towards the east. The dam wall would be fixed between the pillars of the bridge on the downstream side, as it would thus be less likely that the bridge would be hit by floating objects during the rainfall season, and in order to avoid the discharge of stormwater between the pillars and consequently avoiding erosion. At the top of the dam [wall] the metal doors would be articulated at a water level of 1303,3m, with a height of 2,7m and a length of 18,5m; they would operate automatically by means of a system of metal beams and reinforced concrete counter-weights. There would be 39 of these gates and they would allow a maximum volume to flow over the dam wall of 5455m3/s with a normal retention height of 1306m.

Page 22/214 LNEC – Proc.605/1/11926 The “Mission to Southern Angola” projected a value of 4129m3/s at Matala as the flow volume in case of maximum rainfall. On the other hand, Colonel Roma Machado had anticipated in Erickson’s Drift that the maximum rainfall volume would be 5500m3/s. In this way the projected volume for the scheme of Matala was deemed to be acceptable. Even more so, as the structures above the gates would allow the passage of water sheets up to a level of 1307m, 1m above the upper edge of the gates. Even if rainfall would occur that would reach such a level, no damage to the structures would ensue, leaving the dam submerged but in good and stable working condition.

12 deep sluices (under-sluices) were planned, with 1,2m height by 1m width, at a level of less than 1296m.

The technical memorandum that was issued in 1952 stated among other things the fact that, in order to continue with the analysis of this project, it was acknowledged that there was a lack of hydrologic statistics that would allow the definition of the mass of water of the river (interrupted rainfall statistics and lack of regular hydrometric records).

Observations that were carried out over three hydrologic years allowed confirming that the data that were used for the project were on the optimistic side. As a matter of fact, instead of the 69 GWh projected for the two units installed during 1955/56 and 1957/58, only about 18 and 38 GWh could definitely be generated. As an example, in the hydrologic year 1954/55, the minimum flow due to drought was only 4m3/s, which is much lower than the estimated volume of around 24m3/s. The average volume during that year was estimated at 28m3/s, which [also] is much lower than anticipated by the project.

2.4 Master Plan for a Hydro-electric Scheme for the area upstream from Matala (1962)

The Master Plan for a Hydro-electric Scheme upstream of Matala, dated 1962, Figure 1, compiled by Eng. Rui Sanches, was the subject of technical memorandum Nr. 9/63 by the Higher Commission for the Promotion of Overseas Territories. Among the conclusions of this technical memorandum was the intention to promote the continuation

Page 23/214 LNEC – Proc.605/1/11926 of the studies on the hydrographic basin of the Cunene River stands out, with the objective to [ultimately] build multi-purpose improvements.

This plan emerged after the Hydro-electrical Scheme at Matala was put into operation, the first echelon of the Cunene River. Further to the proposal in the 2nd Promotional Plan, the “studies of the source basin of the Cunene River for the regularization of the Matala dam” surfaced.

At that time, it was considered to be of major interest that the study would be implemented on the regularization of the volumes of the tributaries that supplied Matala through other sources of supply upstream, as this scheme would represent a limited guaranteed run off of the available volumes in years of drought, and for the low regularization capacity.

In the scope of this plan longitudinal profiles of the Cunene River and its tributaries, the Cuando and Calai, were made that subsequently revealed major possibilities as far as the supply was concerned. The study on hydro-electric potential led to the conception of a supply system that was structured in 10 echelons.

Eight of the installations were designed upstream from Matala, on the Cunene River and its tributaries Calai and Cuando, three of which with regularization dams that, in conjunction with the dam at Matala, would provide a supply of 2100hm3. It was anticipated that this system would provide electrical power of 307 GWh. The ones that were planned on the Cunene were situated at Gove, one without name, and those at Jamba-ia-Oma and Chivondua. On the right-hand tributaries the plans included the installations at Caringo, Gungue, another one without name and, finally, at Lucunde.

In the year 1963 the hypothesis of a possible cooperation with South Africa was accepted in as far as the regularization works in the source basin of the Cunene were concerned, once an agreement would be reached on the subject of the utilization of the regularized volumes along the border. Thus the hypothesis was expressed that South Africa might participate in the capital of a Portuguese company that would have to be established, with the aim at exploiting the water resources of the Cunene.

Page 24/214 LNEC – Proc.605/1/11926 Subsequent to this study, the compilation of the project for the Gove Dam was initiated, as this project was considered to merit priority of execution. It was decided that supplementing the provision to Matala by means of Gove would be pivotal.

During the month of December of 1965 the Project of the Hydro-electric Plant at Gove was compiled by the Ministry of Overseas Affairs, Province of Angola. It was assessed what levels of electricity could be generated at Matala, if the Gove Dam was built according to the specifications of a full storage capacity at a height of 1580m, 1585m and 1590m respectively. The study that would be carried out according to these three criteria would allow defining the most economical solution for the supply, once an approximate costing for each respective dam level had is identified.

It was established during the project that the average recorded annual rainfall over a 14-year period was 1307mm over the Gove Basin and 1162mm over the Matala Basin.

The hydrometrical elements that were available for the Gove Project were [rather] limited. In addition to those referred to above, [only] sporadic records were taken until the drought of 1954/55 by the Technical Brigade for Promotion and Population of the Cunene. The recording site was slightly upstream from Vial Folgares, below the Matala Scheme, after the junction of the Calonga River with the Cunene. It was also determined that the volume flowing into the Calonga River would be zero during the months from May to October, and that it could be quantified as one fifth for each of the months between November and April.

Limitations to the potential supply of electricity by Matala and compensated by the Gove Dam, have been assumed to cover a guaranteed production that would respond to [the requirements] for a year of drought, or a two-year drought period, depending on which would be more detrimental, with a likelihood to occur 5 times in 100 years, analogous to the criteria that were established by the National Distribution Criteria for the Metropolis. In this way it was established that it was necessary to provide storage to supplement [face] the deficit from one period of drought in an average year, followed by another dry year, with a likelihood of occurrence of 5%, and that a two-year drought period has the same probability [factor].

Page 25/214 LNEC – Proc.605/1/11926

In order to obtain the minimum unusable volume of the dam a specific value was determined for the solid residue, as 200m3.year-1.km-2, and silting was assessed during a period of 75 years. The benchmark of 1556m corresponds to this volume. If one sets the NME at the benchmark of 1563m, which would lead to a dead volume of 210hm3, to a total storage volume of 1198hm3, 1786hm3 and 2574hm3, which corresponds to the NPA heights of 1580m, 1585m and 1590m, this would tally with useable volumes of 988hm3, 1576hm3 and 2364hm3 respectively.

The project study concluded that, for the three alternatives that were considered, the guaranteed volumes at Matala would be respectively 44,3m3/s, 56,6m3/s and 72,5m3/s. The annual amounts passing through the turbine[s] at the Matala station correspond to these values, with 140hm3, 178hm3 and 229hm3, or, otherwise, taking the energetic equivalent of the Matala station at 0,044kWh.m-3, the following guaranteed production levels, 62 GWh, 78 GWh and 101 GWh.

It was then examined if the guaranteed turbinable volume of Matala would not be conditioned by the volume available in an average year, i.e. if the restrictions would not be determined by the volume that would flow from Gove in an average year.

In order to select the heights of the NPA for the Gove Dam, three alternatives were calculated for the volumes of earthworks for the dam wall, their respective construction costs, and the marginal variation in cost and of the respective gains in electricity production at Matala. The conclusion was – within the restrictions of the study – that, the higher the Gove Dam, the more economical the production at Matala would turn out. That is why the height of 1590m was chosen as the level of full storage, regulated by an existing [sluice] gate for higher levels and also because major heightening would result in a specific regularization exceeding 1,5[sic], which would make the refilling of the dam more difficult in future times, after a critical dry period and once it had been totally or almost entirely emptied.

The maximum volume of the Cunene River, at Gove, with a likelihood of occurrence of once in 500 years, was of 2000m3/s.

Page 26/214 LNEC – Proc.605/1/11926 2.5 Water Supply Scheme for the Area Upstream from Calueque (1966)

With the objective to comply with the commitment taken by the Portuguese Government in the Pretoria Accords as regards the scheme for the hydraulic utilization of the Cunene Basin upstream from Calueque, the Task Force for Cunene and Cuvelai was created in 1964.

This team was lead by Eng. Bettencourt Fernandes Moreno, who worked in Angola during approximately ten months to collect field information; it was multi- disciplinary and comprised four sectors: hydrology, agronomics, veterinary science and geology. In addition, the hydrologic-technical staff of the Directorate of Public Works and Communications, Provincial Council for Electrification provided their support, and the River Brigade of Angola, led by Eng. Carlos Góis, agronomic engineers Alberto Castanheira Diniz of the Institute for Agronomic Research and João Heitor Mirrado of the Directorate of Agricultural and Forestry Services, veterinary doctors Gardette Correia of the Directorate of Veterinary Services and Braz Pereira of the Institute for Agronomic Research, in addition to Dr in Geological Sciences, Motta Marques of the Directorate of Geology and Mining Services.

The general orientation towards the studies carried out in the field of hydrology in the Cunene Basin was based on the research paper by Eng. Rui Sanches on the Cunene Basin upstream from Matala, the comments that were made on his work, in particular by engineers Oliveira and Castro, the supply scheme of the basin downstream from Matala as described by Eng. Trigo de Morais, the data provided by the map with the scale 1/100000 with its hydrologic indicators that was produced by the River Brigade.

A schema was presented in 1966 where the Cunene Basin was divided into three sections. One upstream from Matala, one between Matala and Calueque, and the last one up to the river mouth (see Figure 1).

Upstream from Matala the schema does not differ much from the one presented in 1962. In addition to increase the storage capacity of Jamba-ia-Oma, it foresaw two additional supplies, the one at Chissola upstream from the site that was originally planned for station [Nr.] 9, and at the Jamba-ia-Mina Falls, downstream from what was

Page 27/214 LNEC – Proc.605/1/11926 indicated as Chivondua. In this representation the supply of the basin upstream from Matala shows a strong component of hydro-electrical provision, due to better storage conditions, with the view to arrive at annual or inter-annual regularization of [in]flow volumes that would originate from the upper section of the basin. In effect, the losses in volume are rather accentuated in the central section of the Cunene Basin.

There was a marked increase in the storage forecast in comparison to the previous schema, which was the result of improved knowledge in the field of hydrology. For instance, the number of dams was increased from four to six, storage volume increased from 2000hm3 to 5000hm3 and guaranteed electricity production also increased, from 300 GWh to 1000 GWh and the producible from 3000 GWh to 9000 GWh.

For the area downstream from Matala three hydro-agricultural and cattle- breeding installations requiring important specific regularization were taken into consideration, one on Caculavar at Cova do Leão, close to Cahama, a second one on the main stream of the Cunene at Matunto, slightly upstream from Mulondo, and the third on the Colui River, a left-side tributary, at Catembulo, downstream from Cassinga.

In view of the insufficient water resources, with a total of 292.000 hectares that would be suitable for irrigation and that are situated along the valleys of the Cunene between Mulondo and Calueque, of the Colui and Caculavar Rivers, it was decided that intensive irrigation of only 150.000 hectares should be considered. Of these, 120.000 hectares were situated at the right bank of the Cunene, and only 92.000 hectares were irrigated by making use of gravity.

The possibility of pumping water from the Cunene to Mulola Mucope was also considered, and of water that was stored in the Colui Dam to Mulolas do Mui and the Cuvelai. The aim of this was to guarantee water supply all year round and to prevent concentration of cattle from the Mulolas in arid years along the banks of the Cunene.

With the planned scheme at Matunto, with its total volume of 365hm3, a capacity of 111,4m3/s would be assured, to be used for irrigation by gravity in periods of drought, and a minimum volume of 66m3/s would be guaranteed to discharge into the riverbed. At

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Figure 1 – Comparison of the various general schemes in the Cunene River Basin

[Barragem = dam; Estação de Bombagem = pumping station; Áreas regadas = irrigated areas; Zonas de abastecimento de água para o gado = areas for watering of cattle; Central eléctrico = power station]

Page 29/214 LNEC – Proc.605/1/11926 Catembula the maximum volume required for irrigation in times of drought would be 16,5m3/s and, with an average useable discharge of the dam calculated at 11,3m3/s, the future dam with its total volume of 1230hm3 would allow to guarantee such regularization.

The required maximum volume for irrigation at Cova do Leão in drought periods was [calculated at] 21,5m3/s and the average volume was 7m3/s. It would be necessary to plan a dam with 776hm3 capacity, which would provide the possibility to regularize the volume from 7 to 21,5m3/s.

The section downstream from Calueque still needed to be considered after a survey that was carried out by the South Africans with the permission by the Portuguese authorities. The studies that lead to this overall schema required serious reflection and common sense in view of the fact that the available data was quite scarce and the region is particularly difficult and presents a large variety of characteristics. There was no pretension in play that all the small water schemes that could be realized in the basin were taken into account, mainly those that could be established in the minor water courses, but without the large installations that would define any major storage facility and utilization.

A number of other small schemes were also excluded as these were taken care of by the Brigade for the Supply of Surface Water, and whose study and implementation should be ongoing as they might develop other areas that could not be contemplated in the present document.

As a matter of fact, a hydrologic scheme that includes a sensitive area with a size equal to Portugal would necessarily have to take the large schemes into account and to abstain from looking at those of lesser dimension and which may exist in large numbers.

Page 30/214 LNEC – Proc.605/1/11926 2.6 International Agreements in respect of the allocation / sharing of the use of water resources from the Cunene River (1926, 1964 and 1969)

The Cunene constitutes the border between Angola and Southwest Africa from the Ruacana Falls to its mouth. This means that it is an international river over its last 300km. The border line was established by the Accord dated 22 June 1926.

When the delimitation of the frontier was determined in 1926, the scarce water resources of Southwest Africa were taken into consideration and Portugal committed to supply water for humanitarian purposes, and to study the possibility of deviating the river by means of gravity through the construction of a dam at Calueque. At this time the hydro-electric scheme for the Cunene between Naulila and the Ruacana Falls was presented. Whilst the production of electricity was mentioned in the Agreement in some defined instances, the same was not the case as far as the transport of water to Southwest [Africa] was concerned, which was to be the subject of future studies.

In 1962, the Republic of South Africa - quoting the 1926 Accord – requested that negotiations be resumed with the view at supplying water and electricity to Southwest Africa. That is when it was decided to deviate a volume of 6m3/s by means of pumping, which was the volume that was considered necessary for the supply of human beings and cattle in the area in question in Southwest, and this independently from the possibility to come to an agreement on a larger scale that would surpass that of 1926.

When the negotiations were initiated in 1962, Portugal raised the question that, in the framework of relations between the two countries as regards international rivers it was not only the Cunene that had to be considered but all the rivers between Southern Angola and the Southwest African territory, and also the rivers that were shared between South Africa and Mozambique. Portugal defended the point that it was necessary to establish an accord in principle and that would be applicable to specific agreements for each basin that would provide a safety measure for the countries downstream that would always be affected by what was done upstream.

Page 31/214 LNEC – Proc.605/1/11926 In that “accord in principle” that finally was accepted by South Africa, it was established that any international river basin would be dealt with as a whole as regards global purposes of utilization, and as if it was a case of a single country.

Thus the basis of any general plan or scheme that aimed at optimizing the joint supply would have to be discussed in detail, with the possibility that a country downstream might participate in the investments related to an undertaking that might even relate to a project situated quite far from the border, as soon as it would represent an advantage of that country.

An agreement was [subsequently] signed in Pretoria on the subject of the Cunene River Scheme on 13 October 1964, in which amongst other things it was set down that: the study on the supply scheme for the river basin would be carried out by Portugal until the section of Calueque, and downstream from this point it would be undertaken by South Africa; Angola would export electricity that was produced at Matala to the city of Tsumeb in Southwest; South Africa declared that it was interested in hydro- electrical supplies from Ruacana; it was delineated that it would be necessary to regulate supply over and above the Gove once the basin had been examined and that there would be mutual obligation to communicate on the ”main hydrological works” that would [at any time] be carried out in the basin.

The Portuguese side then created the “Task Force for the Study and Implementation of Works in the Cunene and Cuvelai Basins” that we refer to in paragraph 2.5.

Once the reports were completed by the Portuguese – until Calueque – and by South Africa – from Calueque to the river mouth – it became necessary to harmonize the two studies, a task that presented some difficulties that resulted from the differences in criteria and interests as far as the magnitude of the Calueque Dam was concerned. Whilst the South Africans wanted a large perennial dam that would regularize the volumes that came from upstream, the Portuguese maintained that there would only be justification for a small regularization dam, as there were plans for the establishment of dams at Gove, Jamba-ia-Oma, Jamba-ia-Mina and Matunto, on the Cunene, and these

Page 32/214 LNEC – Proc.605/1/11926 would be complemented by those at Cova do Leão, on the Caculavar and Catumbelo on the Colui River on Angolan territory.

As a matter of fact, South Africa suggested building a dam at Calueque with a height of 15m, whereby half of the water would be regulated by each of the neighboring countries, including the possibility to derivate half of the rainfall. Portugal suggested a height of 4m. South Africa asked for the right to derivate 12m3/s. It was then thought that, in order to obtain a regular discharge of 160m3/s, or 420hm3 per month, it would be necessary to have a storage capacity on the Cunene of 2000hm3.

It was the Portuguese point of view that prevailed in the end.

Subsequently to the Accord of 1964, a new agreement was signed in Lisbon on 21 January 1969, with the title “Accord between the Governments of Portugal and the Republic of South Africa on the 1st Phase of the Scheme for Hydrological Resources in the Cunene Basin”.

This accord outlined the optimum joint utilization of the hydrologic resources of the Cunene basin and the following objectives were defined: a) regularization of the flow of the Cunene; b) upgrading of the electricity production at Matala; c) introduction of irrigation [schemes] and the supply of water to people and cattle in the central Cunene region; supply of water to people and cattle in Southwest Africa and the introduction of irrigation in Ovamboland; and e) production of hydro-electricity at Ruacana.

It was also agreed that the partial studies that were carried out by the South African and Portuguese task groups would be jointly considered and that they would serve as a basis for the scheme for hydrologic resources of the Cunene Basin, and that the best setting, characteristics, dimensions and objectives for each component, as well as the program and priorities to be respected in their implementation, would be defined on the basis of technical, economic, sociologic and other relevant considerations that would turn out to be pertinent at the time of decision-making.

The Permanent Joint Technical Commission was then formed, which had a purely consultative character and which had as its objective the study and information of

Page 33/214 LNEC – Proc.605/1/11926 subjects that were related to the accord, and which was made up by an equal number of members from each country.

The 1st phase of the scheme for hydrologic resources of the Cunene Basin consisted of: 1) the dam at Gove, built with a maximum [full] storage level of 1590m above sea level (Portuguese reference level), with the purpose of regularizing the [flow of the] Cunene; 2) a dam at Calueque, built with a maximum storage level of 1098m above sea level (South African reference level) in order to increasingly regulate the flow of the Cunene so that it would be suitable for the future [hydro-electric] station at Ruacana; 3) a scheme for pumping water from the Cunene, at Calueque, for the purpose of people and cattle in Southwest Africa and the introduction of irrigation in Ovamboland; 4) a hydro-electric station at Ruacana and the relevant deviation works for the supply of electricity, mainly to Southwest Africa.

The most important works as far as its consequences were concerned, would be the Gove Dam that would increase the flow of the river in times of drought from between 5 and 10m3/s to 80m3/s. This [level of] flow was to be adjusted once the joint hydrologic analysis was available that was to be carried out at the start of the exploratory phase of the project and, later, at intervals that had been agreed by the Permanent Joint Technical Commission.

As the Gove Dam would be financed by the Republic of South Africa, whereby 50% of the total investment was not to be repaid, Portugal agreed not to take out more than 50% of the regularized flow, for non-conservative purposes, i.e., for irrigation, or in other words, a flow of 40m3/s.

The costs of construction of the works at Calueque and Ruacana were funded in their entirety by the Republic of South Africa.

The quantity of water that could be withdrawn by the pumping scheme at Calueque during any given week would be limited to half the natural flow of the river, at the point of extraction, during the week in question, subject to a maximum flow of 6m3/s.

Page 34/214 LNEC – Proc.605/1/11926 According to the agreement, the South African authorities would have perpetual exclusive use of the flow of the river once it had been regularized by the construction of the dams in the 1st phase, from to the upper edge of the deviating dam [wall] at Ruacana up to the bottom of the Ruacana Falls. The Republic of South Africa would pay royalties to Portugal for the electricity that was produced at Ruacana. The respective rate would be based on the forecast for electricity production, estimated by the South African authorities, and calculated in order to provide an aggregate over a period of twenty years, that would be equivalent to the sum of twenty equal annual installments, for amortization and interest, to be paid by Portugal in respect of the loan that was extended for the Gove Dam. This calculation would be based on half the discharge at Ruacana once regularized by Gove, allowing that water would be only withdrawn upstream from Ruacana, and that this [arrangement] would be reassessed every five years. For the first five years the rate would be 0,11 Rand Cents per kW/h that was produced. After amortization, the royalty would be fixed at 0,5 Rand Cents.

At the beginning of 1973, South Africa advocated the initiation of new negotiations with the view at increasing the discharge of the river into Calueque. These negotiations were to take place in Lisbon during July of 1973, with unknown content except for the admission on 25 April 1974 that no formal results had been reached.

There were indications that South Africa intended to conduct the discussions in accordance with the “Helsinki Convention” on the subject of international rivers that was produced in 1966 by the International Law Association.

2.7 Studies and Projects carried out after 1969

The Planning Office for the Cunene (Gabinete do Plano do Cunene – GPC) was created on 25 August 1969. At that date another variant of the Cunene Scheme, by Carlos Oliveira e Castro, was already in existence. It was stated that this would be based on a multi-purpose context, i.e. for hydro-electrical, hydro-agricultural, water supply (for people and cattle) and navigational purposes.

This Office was divided into three Services: Agronomic, Sociologic and Civil Engineering. The Agronomic Services would expand the agro-economic studies, identify

Page 35/214 LNEC – Proc.605/1/11926 viable crops, analyze the respective market demand and identify the type of investigation that was to be carried out. They would establish a Research Center for the Cunene, at Vila Roçadas, for the purpose of testing produce and they would have an agricultural extension post at Camba. The Sociologic Services would make use of survey by questionnaire and explore the populations around the sites of future hydro-agricultural schemes. The Civil Engineering Services would have the task to develop projects for the schemes, including cartographic, topographic and geologic surveys.

In September of 1970 there was already a pumping scheme at Calueque, which had been designed by South Africa, and in November of the same year – during the 1st meeting of the Coordinating Committee of the GPC – priority was given to the scheme at Jamba-ia-Mina. Other studies were carried out on the subject of the irrigation scheme at Quiteve-Humbe, with 20000 hectares, and, in parallel of the cattle-watering scheme at Quiteve, with 90000 hectares; [they also included studies on] the cattle-watering scheme at Cafu and the rural water supply for Colonato de Capelongo, and the preparatory works had already been initiated for the construction of the Gove Scheme.

During 1971 and 1972 the previously mentioned studies carried on, as did the ones for Jamba-ia-Oma, Matunto, Calueque (on the sociologic aspects), Chibia (Gandjelas) on the Tchimpumpunhime River, Cova do Leão, Luandege (between Calueque and Ruacana) and for smaller schemes like the ones at Quipungo, Humpata, Cacondo and Naulila. The works carried on at Gove.

In 1972 the problem with pollution of the Cunene and Colui rivers was reported, which resulted from the mining activities at Cassinga.

During 1973 the socio-economic studies carried on with surveys conducted in [the area of] Cassanja-Quiteve-Mulondo, with the collaboration of the Chiulo Mission, and a Plan for Social Advancement was elaborated in October of 1974.

The prior studies regarding the schemes at Jamba-ia-Mina and Jamba-ia-Oma were presented respectively during December 1973 and June 1975. The former was expanded upon during October 1974.

Page 36/214 LNEC – Proc.605/1/11926 The project for the scheme of Jamba-ia-Mina was specified as a mixed dam construction using concrete and soil, with a maximum height of 23,5m, a stormwater overflow for 3200m3/s, a water outlet and a basic discharge structure that would be incorporated in the concrete section of the dam, reinforced conduits, underground station, stabilizing vent and an emergency passageway. The NPA was set at a level of 1420m, which resulted in a dam with a total capacity of 568hm3, with an average annual discharge of 3.482hm3 originating from a basin with [a surface of] 12.336km2. [these figures correspond to the original text…]

The average contribution by the tributaries during the period 1933 to 1972 was estimated to be 110m3/s, with a minimum recorded of 5m3/s. The regularization at Gove resulted in 92m3/s, and the combination Gove plus Jamba-ia-Mina in 98m3/s. With an available potential of 126 MW, the potential average electricity production was 622 GWh. The objective was to produce a permanent minimum flow of 80m3/s downstream from Matala. The project analyzes also the introduction of the scheme at Jamba-ia-Oma that would regularize 78m3/s.

The previous study for the scheme at Jamba-ia-Oma defined the project as being made up by a mixed dam made up of concrete and soil, with a maximum height of 47m, a stormwater overflow for 2155m3/s, a water outlet and a basic discharge structure, situated in the concrete section of the dam, reinforced conduits, a power-station at the foot of the dam and an open-air restitution canal. The NPA was defined at a level of 1520m, which resulted in a dam with a total capacity of 1088hm3, for a total average annual discharge of 2719hm3, deriving from a basin [with a surface of] 8620km2.

By force of Decree/Act Nr.602/72 dated 29 October, the Planning Office for the Cunene was transferred to Angola.

A number of works were halted in April 1976, in particular the dam at Gandjelas, the organization of Quiteve-Humbe, the organization and rural water supply scheme at Calueque (right bank) and the weir [dam] on the Cué River.

The Gove Dam had been provisionally abandoned.

Page 37/214 LNEC – Proc.605/1/11926 3. SUPPORTING DOCUMENTS

When the Initial Report was compiled in 1990, LNEC received a series of documents. It was noted at the time that these documents would be valuable as it was the only documentation that would remain on the subject of the Cunene.

The references of these documents are listed in Appendix 2.

The documents were categorized according to the following subjects: - Matala Scheme, Ministry for Overseas Affairs, 1951; - Rainfall and Draining; - Volumes, limnometric levels, and Hydrographic Basins; - Reports on the International Hydrologic Decennium; - Maps of the Cunene River; - Projects on the Cunene River; - Programs for Reconstruction; - Proposals regarding the Cunene River; - Financing and Budgeting Processes; - Meteorological Observations – 1957/67; - Meteorological Information – 1968/1975; - Climatologic Information – 1959/1972; - Diagram of hydraulic supply, 1966/67; - Project for the hydro-electric scheme for the Cunene, 1965/67; - Jamba-ia-Mina Scheme, Coba, 1973 and 1974; - Jamba-ia-Oma Scheme, Coba, 1975; - Tender for the link between Matala-Jamba-Tchamutete.

During the execution of these studies other documents were found that existed in various libraries in Lisbon, and in particular in the Institute for Scientific and Tropical Research (Instituto de Investigação Científica Tropical).

Among the documents that were used, those contained in the “Bibliografia analítica sobre o meio físico potencialidades e utilização da terra na bacia do Cunene” [„Analytical bibliography on the physical environment and utilization of the soil in the Cunene Basin‟], by Eng. Castanheira Diniz, Appendix to Volume 4 of the 1st Report. From these the ones that were encountered in Luanda, at the National Directorate for Water Affairs in the Secretariat for Energy and Water and in the Department for Physical Planning of the Ministry for Planning, and finally, at the Institute for Agronomic Research at Huambo.

Page 38/214 LNEC – Proc.605/1/11926 It should also be noted that the library of the National Directorate for Water Affairs in the Secretariat for Energy and Water, at Luanda, apparently possesses the most complete set of documents that refer to the Cunene. Mr. Paul Emílio has to be mentioned, who has maintained these documents and without whose care and dedication it would not have been possible to preserve these important records.

4. DESCRIPTION OF THE HYDROGRAPHIC BASIN

4.1 Location

The source of the Cunene River is situated on the central high plateau of Angola, close to Huambo. Its mouth is located 60km to the South of The Bay of Tigers, on the Atlantic Coast (Figures 2 and 3). The river crosses four provinces: Huambo, Huíla, Cunene and Namíbe.

The hydrographic basin of the Cunene River is one of the major systems in Angola (together with the Zaire, Zambezi, Cubango and Cuando Rivers) and has an elongated form, spreading between the parallels 13º 30‟ S and 18º 02‟ S, and the meridians 11º 48‟ W and 16º 20‟W.

The hydrographic basins that are adjacent to the Cunene River Basin are: to the north, those of the Queve and the Cuanza; to the east, those of the Catumbela, Caporolo, Bentiaba, Giraul, Bero and Curoca; the Harusib to the south and the Cubango and Cuvelai to the east.

4.2 Topography

The cartographic work that is available and that covers the area of the hydrographic basin of the Cunene River is the Map of Angola, at the scale of 1/250000 (published by the former „Missão Cartográfica de Angola‟ that is nowadays integrated into the Institute for Tropical Research). The area of the basin is covered by twenty-one sheets. The photogram-metrical survey that was the basis of this Map was carried out between the years of 1957 and 1959.

Page 39/214 LNEC – Proc.605/1/11926

Figure 2 – Location of the Cunene River Basin [Localização geral da bacia = general location of the basin]

Page 40/214 LNEC – Proc.605/1/11926

Figure 3 – The Cunene River Basin and its hydrographic grid

[Curvas de nível (altitude em m) = Level curve (height in m) Linhas de água = water lines Limite da bacia hidrográfica = boundaries of the hydrographic basin]

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The cartography of Angola at a scale of 1/100000, with equidistant level curves at 50m, was established by the team of the Geographical and Research Missions for Overseas Territories. It was obtained from an aerial survey of the region that embraced the entire hydrographic basin of the Cunene River upstream from Matala, during 1965. The basin is represented on 57 sheets, included between the sheets with numbers 255 and 466. 12 of these correspond to Namibian territory, without cartographic information that would be accessible to date.

For some localized studies, like for example the one at Gove, aerial surveys were made in 1963 to the scale of 1/10000 by TECAFO, and these were related to the geodesy of the province in as far as both planometry and altimetry are concerned.

As there is no recent cartographic information this might be updated by means of satellite images. Such images could also provide thematic information that is not contained in the maps, like for instance the type and distribution of vegetal cover, the type and distribution of soil utilization, etc.

In view of the extent of the work to be carried out and the objectives that needed to be attained, it was judged to be more adequate – both from technical and economic points of view – to opt for the use of information that was obtained from the “Thematic Mapper” (TM) sensor, on board of Earth Observation Satellite Landsat-5. The digital images that this system gathered have a good spectral resolution, and its special resolution (30x30m) is compatible with the distribution, respectively occupation, of the territory by various subject matters that it was the aim to identify.

The hydrographic basin is covered by eight Landsat TM images. These can be obtained via optical discs, by computer.

4.3 Hydrographic morphology, relief and structure

Angola consists mainly of high plateaus and high peneplains, with average altitudes of between 1000 and 1500m, that can be classified in five morphologic

Page 42/214 LNEC – Proc.605/1/11926 elements, whereby the altitude increases with the age of the geological formations that have formed them [the higher the plain, the older the geological formation].

The oldest of the five morphologic components is the Cadeia de Montanhas Marginal („Marginal Mountain Range‟) – Type V – that is represented in the Cunene in the mountainous area of the Humpata and the entire mountain range that stretches from Lubango to Huambo, with altitudes exceeding 1500m. These rise abruptly from [levels of] around 200 to 250m, from Type IV topography.

The Região Planáltica („High-Plateau Region) – Type IV – also called the African High Plateau, is a flattish area, with monotonous relief, lightly undulated and incised by broad valleys, is represented along most of the Cunene River Basin, with altitudes of between 1200m and 1800m, until the vicinity of the Ruacana Falls.

The Região Sub-Planáltica de Transição („Transitory Sub-tableland Region‟) – Type III – the area with altitudes that vary between 1000m and 500m, and that represents the border to the previous, irregular zone, is characterized by a flattish area that is badly drained, and that extends between the region to the east of Ruacana and the Serra da Cafema.

The Região Baixa de Transição („Lower Transitory Region‟) – Type II – is a peneplain, slightly sloping towards the coast, with a gradient of 0,3%, in which residual reliefs like escarpments, platforms and ridges can be found.

The Região Litoral (Coastal Region) – Type I – in Southern Angola has a width of between 35 and 55km, with altitudes below 300m, and a gradient in the order of 0,8%, where the area of the river-mouth of the Cunene is situated.

The result of the morphological characteristics of these Types is that the hydrographic basin of the Cunene River can be classified into three zones with well- defined characteristics:

 The North- Northwest Zone, upstream from Matala: A region with pronounced reliefs, with altitudes varying between 1300m and 2100m.

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The occidental edge of the basin, in particular in the area around Humpata, is made up by a rounded massif, with a north-south orientation, that is associated with the Cadeia Marginal de Montanhas („Marginal Mountain Range‟), with accentuated gradients towards the west, that are particularly visible in the Serra da Chela, which forms an escarpment with an altitude of around 1000m. This Cadeia Marginal de Montanhas extends in high reliefs from the Lubango area to the high plateau of Huambo. It borders along the west-northwest side on the Cunene River Basin and extends progressively more inland on its way north, and gradually occupies the entire basin area from Matala until Huambo.

 The area between Matala and Calueque, at the beginning of the border section: vast high plateau with altitudes of between 1000m and 1300m.

The Região Planáltica („High Plateau Region‟) develops effectively in two intermediate platforms that correspond to distinct lithologies. A large part of this tableland can be found above the crystalline rock and ancient (Pre-Cambric) meta-[or post-]sedimentary layers, after a relief of Jurassic pleneplains had been remodeled by more recent activity; the remaining part develops on accumulated material of the Kalahari and Quaternary types that form an extended and flat surface (that is generally indicated by tunda [„thrashing ground‟]) of the Pleistocene Age, with an incipient drainage system, and where a variety of chanas, mufitus and ecangos can be found. The chanas [oshanas] are wide shallow and flat-bottomed valleys with low banks, somewhat swampy and marshy; the mufitos are slightly higher areas that are situated around the chanas and that form their rim; ecangos are closed depressions that have developed above the mufitos. The planaltic zone with the rolled tertiary and Quaternary formations – that occupies the central-south-eastern region of the Cunene River Basin – is separated from the peneplain that has developed in the crystalline rock by a small escarpment of 10m height.

 The area downstream from Calueque: corresponds to that part of the hydrographic basin that is drained by the international section of the river; it presents accentuated reliefs and altitudes of between 1000m down to sea level.

Page 44/214 LNEC – Proc.605/1/11926 In this southern region the granite reliefs are usually rounded hillocks, showing sometimes cavities that may reach important dimensions; the limestone consists of reliefs with steep slopes, with cornices and gradations, deeply incised by a large number of small valleys; on its side, the schist and quartzite rock give rise to rather accentuated reliefs that are deeply scored by erosion [by the drainage system].

The separation between the High Plateau and the Região Sub-Planáltica de Transição („Transitory Sub-Planaltic Region‟) is made by an escarpment that sometimes reaches heights that exceed 650m. Erosion is very severe in the western and northern edges of the Planaltic and Sub-Planaltic Regions, which means that the border area of the peneplain is already rather decayed. As opposed to the Region of the High Plateau where the rivers are rather less enclosed, the waterways here are more hemmed in, in particular close to their sources. The escarpment area shows erosion activity which is less strong on the eastern bank as compared to the western, and is affected by important slope deposits.

The partition between the Região Baixa de Transição („Lower Transitory Region‟) and the Coastal Region is made up of the heights at the occidental side of the Cafema Mountain Range. The Coastal Region has typically rather modestly accentuated reliefs and a rather summary stormwater drainage system. The Coastal Desert Region of Namibia slightly influences the final section of the Cunene River, in particular the area around its mouth.

Thy hydrographic system of the Cunene River Basin is mainly of a dendritic nature in the entire region upstream from Osse and, largely rectilinear to the south of that region. In the area where the Kalahari and Quaternary outcrops occur, the drainage system is formed by incipient waterways, of a rectilinear shape and with often rather badly defined beds, irregular longitudinal profiles and with some sections where the slopes are inverted in relation to the direction of the escarpment; it was noted that this rectilinear tendency can also be found to a certain degree in the area upstream from Osse. The dominant orientations are NW-SE, but one may also encounter E-W, SW-NE, and N-S, whereby it is supposed that many of these waterways are boxed in by subjacent fractures that extend to the crystalline basement. Many of these temporary waterways – mulolas – in the area of the Quaternary deposits and of the Kalahari outline

Page 45/214 LNEC – Proc.605/1/11926 are strongly meandering along the chanas [oshanas], with a frequent occurrence of ponds that are the result of abandoned meanders. In the area that is occupied by rolled deposits depressed points can be commonly found where water has accumulated – the etalas – that have sometimes developed along the incipient beds of the waterlines. The same type of rectilinear drainage system, with similar orientations to those mentioned above, occurs in the crystalline basement, where the system is already more defined and developed, as it has in many instances emerged along tectonic accidents; however, in the areas of schist outcrops there may exist a certain tendency to dendrite drainage. In the sub-planaltic area the drainage system is well boxed-in, in particular at proximity of the escarpment, where phenomena exist whereby some waterways capture others.

The region around Osse-Mucope also marks the boundary between the symmetric aspects of the basin. As a matter of fact, the Cunene River Basin has a strong asymmetry downstream from the axis Osse-Mucope; effectively, downstream from this axis the occidental sector is rather vaster and as far as the development of the drainage system is concerned than the eastern side, at least as far as the Angolan territory is concerned. In the final sector (the border with Namibia), the drainage network is rather lesser in extension and in density of waterways, which indicates the predominating conditions of drought in that sector. This diminution of the density of drainage can be felt to the south of Quiteve, in particular towards the oriental bank, in as far as there are no significant waterways on that bank within Angolan territory from Tocolo onward.

The Cunene River Basin has a total surface of between 105.350km2 and 106.500km2 and, according to the sources, the major part of 92.400km2 is situated on Angolan territory, and the remainder is in Namibia.

In the area that is affected by the Cunene River Basin the majority of rivers are temporal stormwater drainage, drying out during the „cacimbo‟ season (from May to August), with the sole exception of the Cunene River. As a matter of fact, the latter traverses the entire south of Angola, where the only perennial rivers are specifically the Cunene, the Cuando and the Cubango.

Page 46/214 LNEC – Proc.605/1/11926 The Cunene River has its source in the High Plateau of Benguela, in the district of Huambo, close to Boas Águas. Its name signifies in local dialect: large river.

Its length is understood to be between 945 and 1100km, depending on the sources [one consults]. Its width can attain between 5 and 8km at Humbe and upstream from this point.

The area of its hydrographic basin up to Matala is 27.526km2 and 83.382km2 up to Calueque.

The course of the Cunene River can be divided into three sectors: in the first, with a length of 550km, the river develops integrally on Angolan territory, with a general direction from north to south, until the confluence with the River Mui; in the second sector which extends until Ruacana, also within the Angolan territory and with a length of around 200km, its direction changes to NE-SW; from this point to the mouth there is the final sector with around 350km, where the river forms the border between Angola and Namibia and is predominantly orientated from east to west (Figures 3 and 4).

The first section consists of the initial part of the Cunene River, of about 320km in length, which is situated upstream from Matala. It is boxed in, in the mountainous area to the north of the hydrographic basin, shows a pronounced slope, with a rocky bed and rapids (whereby the ones at Jamba-ia-Mina stand out). The area of the hydrographic basin that is drained by this sector shows a well-marked drainage system, made up by permanent draining channels whereby the Cunhangamua, Calai, Cuando, Cunje and Qué are prominent on the right side of the river, and the Cusso on the left.

In the intermediary section with its length of 380km, between Matala and Calueque, the bed of the Cunene River has a rather smooth gradient with a difference in height of just 130m. The Cunene presents here the characteristics of a river traversing a plain: alluvial bed that is predominantly sandy, and a flood plain with a width of 2km.

This plain is noted mainly along the right bank, giving rise to the formation of small lakes. The tributaries on the right bank of the Cunene River in this section are the Calonga and Caculavar and the tributaries on the left bank are the Osse and Colui

Page 47/214 LNEC – Proc.605/1/11926 Rivers. The Caculavar drains a vast area that extends from the area of Lubango until Xangongo, embracing the Drainage System of Mulola Mucope, with water lines in the direction W-E that are more or less parallel; these waterways flow into the Mulola Mucope that runs from north to south in parallel with the Cunene. All the waterways of the hydrographic basin that are drained via the Cunene are of a temporary nature.

From the Matala Falls to Ruacana, the river is navigable for ships with a draught not exceeding 0,9m, from the upper part of the Iacavala Falls, 45km upstream of Ruacana, to the Matala Falls, with the exception of a small section downstream from Capelongo that might be economically be adapted to become navigable.

Along the final section, downstream from Calueque and with a length of 350km, the river has a gradient of around 110m. In this section the river is rather boxed-in, with sizeable falls and extensive rapids. The right bank of this section is drained by the Elephant River and by small temporary tributaries towards the mouth, more like stormwater drains. The left bank of the hydrographic basin in Namibia is drained by the Omubonga and Otjunjange Rivers.

The Brigade for the Research of Rivers in Angola, domiciled at Sá de Bandeira, has published in 1962 the Hydrographic Survey on the Cunene River, at a scale of about 1/5000. On 34 sheets (not covering the entire extent from the Ruacana Falls to Montenegro) a survey was made of the minor river beds, indicating their depth but not the date of survey, and referring to the existence of rock foundations where these existed. There was mention of depths of between 0,5 and 5m, in a typical succession of rivers with falls and whirlpools. Over an extension of the river exceeding 160km, its width fluctuated between a minimum of 50m up to a maximum of 175m, when there was just one canal, with a predominant width of 100m. In the areas where there were two canals the width could broaden up to 500m, encircling islands with a width of up to 300m

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Figure 4 – Longitudinal profile of the Cunene River

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The Brigade for the Research of Rivers in Angola, domiciled at Sá de Bandeira, has published in 1962 the Hydrographic Survey on the Cunene River, at a scale of about 1/5000. On 34 sheets (not covering the entire extent from the Ruacana Falls to Montenegro) a survey was made of the minor river beds, indicating their depth but not the date of survey, and referring to the existence of rock foundations where these existed. There was mention of depths of between 0,5 and 5m, in a typical succession of rivers with falls and whirlpools. Over an extension of the river exceeding 160km, its width fluctuated between a minimum of 50m up to a maximum of 175m, when there was just one canal, with a predominant width of 100m. In the areas where there were two canals the width could broaden up to 500m, encircling islands with a width of up to 300m.

The section of the Cunene River between the Montenegro Falls and the river- mouth was also re-examined, and the approximate position of its rapids was noted. It was recorded that the level of the water would have an influence on the quantity and intensity of these rapids. It was concluded that it was not possible to navigate this section.

4.4 Geology

The description of the geological elements of the Cunene River Basin, from the most recent to the oldest, is given according to the following subdivision (Figure 5):  Undifferentiated Quaternary – are deposits of a continental nature in practically the entire area of occurrence in the Cunene River Basin. They are represented by alluvial, eluvial and other recent deposits. These are mainly clayey sand to sandy clay deposits, which reveal themselves as black clay as a result of the alteration of the underlying crystalline rock. They contain more or less rounded clasts that originate from that rock, in the area that is drained by the Caculavar, where this and some mulolas flow across the Gabbro-Anorthosite Complex. In some areas these alluvial deposits may have a more sandy character. Fluvial terraces containing clay may also occur, as well as slopes, made up of gravel, with rounded boulders of crystalline rock, well-consolidated conglomerate and quartzite rock, whereby the nature of these deposits depend on the underlying

Page 50/214 LNEC – Proc.605/1/11926 bedrock. The Quaternary is further represented by deposits of calcrete, ferricrete and silcrete, that may cover the sediments of the Kalahari Sequence or the beds and banks of rivers and etalas that flow over such formations; the latter are pale- coloured sandy deposits which are well-sorted rounded and not consolidated, and may reach a considerable thickness; occasionally more impure clay and diatomaceous deposits may also occur. Laterite may be represented as well.  The Kalahari Sequence – consists of deposits of Cenozoic deposits of continental origin, with ages that extend from the beginning of the Palaeogene to the end of the Neogene. They reach a thickness of up to 600m in the area to the east of the Cunene River Basin, but become progressively thinner towards the west. In the Tunda, the thickness is reduced to about 100m, further on it levels out with the crystalline basement. Covering the crystalline basement – in most instances overlying clayey paleosoils – one will find deposits that blanket its palaeorelief, and that fill a vast sedimentary basin with an overall dip towards the south. The basis of these deposits is made of sandstone and more or less silicified conglomerates, which can also have a calcareous matrix, covered by sandy clay that has partially calcified. The Cunene River Basin is characterized by sandstone deposits and brittle clayey sandstone. At places, limestone nodules and localized insertions of significantly clay-bearing red sand and also surface crusts of white limestone that is partly silicified occur. The red conglomerates that shape the base of the sandstone deposits have elements of the underlying Gabbro-Anorthosite Complex. They may vary laterally towards compact, white or greenish sandstone which weathers to a red color through alteration. The bulk of the sandstone, brittle sandy clay, silicified clay and conglomerate has settled discordantly on red sandstone that formed through the alteration of the underlying crystalline rock. Localized occurrences of dolomite or more or less pure limestone may be encountered, and have eventually become karstified, like in the case of the region of Erickson‟s Drift near the river‟s mouth. At surface, the Kalahari Sequence is evident through the presence of fine white or pinkish sand, or white calcrete crusts that are at times silicified, and calcareous sandstone. In general, one might subdivide the Kalahari Sequence according into two groups:

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Figure 4 – Geological map of the Cunene River Basin

Page 52/214 LNEC – Proc.605/1/11926 LEGEND:

PRE-CAMBRIAN CENOZOIC

 Undifferentiated Quaternary  Sedimentary Formations of the Kalahari and Deposits of Southwest  Meta-sediments of “Espinheira”  Norites and Dolerites of the Pan-African Orogeny  Formation of Leba-Tchamalindi  Group of Chela  Red Granite of Southwest  Granites of Chicala-Cacula  Porphyroblastic Granite, Type Quibala  Biotic Granite of the Central Region  Riolites of Eleva-Catabola )  Formations of Chivanda-Negola ) Supergroup of Oendolongo  Gabbro-Anorthosite Complex  Schist, Transition- and Miscellaneous Volcanic Rock of the Limpopo- Liberian Orogeny  Granito-Migmatic Complex of the Limpopo-Liberian Orogeny  Granites, Diorites and Grano-Diorites of the Limpopo-Liberian Orogeny  Gneisses and Migmatites of the Limpopo-Liberian Orogeny  Crystalline Limestone of the Limpopo-Liberian Orogeny  Schist-Quartz Complex  Border

Page 53/214 LNEC – Proc.605/1/11926  The Upper Kalahari Sequence or the Sequence of Ochre Sands – originating in the Neogene, it occurs generally in the higher-lying regions, all over the region where the overlying Quaternary has been eroded. This implies practically the whole area along the planaltic region of the central section of the Cunene River, south of Calumbinga, Matunto, Chibemba, Cahama and south of Ediva up to the border with Namibia. The upper Kalahari sequence comprises fine to average- sized, well-sorted sandstone and clay deposits, with mainly siliceous cement, colours vary between crème, yellow and red. At surface these deposits are distinctly sandy, disintegrated and mobile – They have pale or grayish colours, and sometimes present phenomena of lateritization.  2. The Lower Kalahari Sequence or the Sequence of Polymorphous Sandstone – dating from the Palaeogene, it emerges at the edge of the Upper Kalahari Sequence, in narrow and long belts. In the area of Chibemba and somewhat to the north, in the region of Matunto, between Cahama and Chicusse and in the region to the east of Cavaláua. It appears along the contact between crystalline basement and the more recent residual sequences, in the valleys of deeply incised waterways and at the bottom of some etalas, that are in direct contact with the crystalline basement, and which may form tabular reliefs with escarpments of up to 10m in height.  The Lutoa-Cassange Formations – are dated between the Carboniferous Age and the end of the Jurassic, they are of a continental nature and occur along the international section of the Cunene River, along a belt of some kilometers in length that is situated upstream from Serra da Cafema.  Igneous- Mesozoic Rock – olivine basalt, andesite, dacite, microdiorite, dioritic porphyrite and norite, andesite in the region of Dinde-Lola and at Lubango; olivine basalt, and the eruptive complexes of Bonga and Tchivira (carbonatite, carbonatitic feldspar breccias, apatite-carbonatite rock, eruptive breccias that are non-carbonatitic, phonolite, tinguaite, trachyte, ijolite, melteigite, urtite, microsyenite, syenite, nephelinic syenite, syenodiorite, and a variety of other alkaline rocks). In the region of the source basin of the Mungongo River one will find phonolite and, in the areas around Huambo and Caála, among others, kimberlite crops out. Basalt and dolerite occur in the area of the Matala Dam as well as breccias that are more or less associated with faults. Other kinds of igneous rock may occur with veins of quartz, aplite-pegmatite, lamprophyre, and

Page 54/214 LNEC – Proc.605/1/11926 basic volcanic rocks, all of poorly defined age. The dolerite occurs not only in dykes, but also in sills that cover the underlying crystalline basement. The igneous rocks tend to fill the tectonic structures that predated their intrusion. Large pegmatitic lodes have also been recorded to the north of Chiquaqueia. Aplitic intrusions may occur in association with pegmatic intrusions.  Igneous Pre-Permean Rocks – rhyolite and associated rocks, red granite and granitoid porphyry. Their basis is mainly igneous. These rocks occur in the area around Dinde-Lola and Lubango. There may also be various igneous rocks like: lamprophyre, tonalite, peridotite, hyperite, aplite, pegmatite, diorite and granitic porphyrite.  Pre-Cambrian Crystalline Basement – this is the third largest system present in the Cunene River Basin (the other two are the Quaternary deposits and the sedimentary Kalahari Sequence). It appears all over the western and southern regions of the Cunene River Basin, to the west of the contact with the tertiary Cenozoic and Quaternary formations; it is also encountered to the east, in a vast emergence that extends between the Jamba and Munduma Rivers, between Monguira and Vila Flor, and in addition, in sections that are interspersed by the Quaternary right up to the area around Huambo. It comprises marble, quartzite and various meta-sedimentary rocks, as well as igneous and migmatitic rocks dating from 2900 million years to the boundary of the Palaeozoic Age. These terrains give true evidence of the various Pre-Cambrian orogenies that affected the region: Pan-African, Kibaran, Eburnean, Limpopo-Liberian. Naturally, the oldest rocks have undergone a number of metamorphic events. They are therefore much more intensely fractured in comparison to the younger rocks. The fractures are often filled with olivine dolerite, lamprophyre, diorite, aplite and pegmatite. The Pre-Cambrian crystalline basement can be classified into the following groups occurring in the Cunene River Basin, starting with the younger ones and leading to the oldest: 1) Damara Belt („Meta-sediments of Espinheira‟); 2) Leba-Tchamalindi Formation 3) Chela Formation or Group; 4) igneous rock from the Pan-African orogeny; 5) igneous rock from the Quibarian orogeny; 6) granites and gneisses from the Eburnean orogeny; 7) the Supergroup of Oendolongo, associated igneous and meta-sedimentary rock; 8) Gabbro- Anorthosite Complex and associated rocks; 9) meta-sediments and volcanic rocks of the Limpopo-Liberian orogeny; 10) granitic-migmatitic complex; 11)

Page 55/214 LNEC – Proc.605/1/11926 granites and gneisses of the southwest and 12) metamorphic sequence of southwest.

4.5 Climate

Angola is situated in the tropical climate belt and can be divided into the following specific climatic zones:  The Zone of Dry Steppes and Savannahs – a semi-arid tropical climate zone. It is represented in the Cunene River Basin by the region between the Monte Negro Falls and Matala.  The Humid Savannah Zone - an area with a prolonged rainy season but in which the dry season can last up to 4 or 5 months. In the Cunene River Basin this climatic zone can be found upstream from Matala.  The Desert Zone – to the extreme south, is influenced by the Kalahari and Namib Deserts. The Rio Cunene Basin embraces this climatic zone in the region between the Monte Negro Falls and the Coastal Region.  The Coastal Zone - the entire sea front; it is strongly influenced by the Benguela Current. As far as the Cunene River Basin is concerned, this climatic zone can be found at the river mouth.

The climatic classification by Thornthwaite divides the Cunene River Basin into five climatic zones, see Figure 6. The Humid Zone, on the Upper Cunene, develops from the beginning to the areas above 1300m. The Sub-humid/humid zone is situated as a continuation of the previous zone until the parallel Lubango-Menongue. Towards the south, the Sub-humid/dry zone occupies a large part of the central basin of the Cunene, corresponding to the vast surface of altitudes of between 1200m and 1300m that gradually rise towards the east to a height of 1500m. The Semi-arid zone, from the confluence of the Mui River to Ruacana, embraces the bulk of the central Cunene Basin, corresponding to altitudes of between 1100m and 1400m at the western rim and to between 1000m and 1100m along the course of the Cunene, which indicates a quite gentle slope of the surface. The Arid zone can be found from Ruacana to the mouth of the river; it practically coincides with the lower Cunene Basin and expands more or less from altitudes of around 1000m to sea level.

Page 56/214 LNEC – Proc.605/1/11926 The climate of the hydrographic basin of the Cunene River is, as we have seen, quite diversified and depends on three basic factors: altitude, proximity to the center of diffusion of dry winds that constitute the Kalahari Desert, and latitude.

The increase in rainfall, from the humidity in the air and the reduction in temperature are conjugation factors by the increase in altitude, the distance from the dry zone of the Kalahari and a decrease in latitude. It has been ascertained for these reasons that a decrease in the average annual temperature of the air has been recorded of between 24 and 19ºC, from Ruacana to the Huambo Region (see Figure 7). In the south the hydrographic basin also has experienced a decrease in the average annual air temperature as it approaches the river mouth, and one may find a variation from 24 to 18ºC. This decrease is due to the effect of the cold Benguela Current that also causes an increase in the humidity of the air. In the area of Lubango the average annual temperature varies between 14 and 16ºC. It is therefore confirmed that lowest temperatures occur on the high plateau and along the coast. The temperatures increase from the north to the south until more or less the area of the river mouth, where they then decrease slightly.

The annual variations in temperatures are not very pronounced, with a maximum of around 6ºC in the northern zone of the basin but increasing towards the south. The cool period takes place for a large part of the Cunene River Basin from May to August (the cacimbo season), with the months of June, July and August being the coldest; the hottest period for most of the basin is September to April, and it may be shorter downstream from Ruacana.

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CLIMATIC ZONES Humid…………………....1 Sub-humid humid………2 Sub-humid dry ………….3 Semi-arid……………...…4 Arid……………………….5

Figure 6 – Climatic zones in the Cunene River Basin

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Figure 7 – Average annual temperatures in the Cunene River Basin

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Figure 8 – Average annual rainfall in the Cunene River Basin [values in mm)

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The average annual rainfall decreases from the north to the south, from around 1400mm in the northern section of the basin, to quantities of less than 50mm close to the river‟s mouth. The annual rainfall is not uniformly distributed, neither during the year nor from one year to the next, and it is concentrated in the humid season that extends from October to April; during the dry season – from June to August – one usually does not record any or hardly any rainfall, with the months of May and September as transitional periods. The tendency is also confirmed that the most humid season becomes shorter, starts later and ends earlier, the higher the altitude becomes. Normally there is one drier month during the wet season, which coincides with the month of February. The winds are normally weak and have a predominantly SE direction. The average annual evaporation – [measured] at the Piche trough – indicates that the lowest evaporation takes place in the coastal area and in the northern and central sections of the basin, with measurements of around 2500mm, with an increase in these values from north to south and from coast to inland, and with the highest measurements (more than 4000mm) in the Ruacana area. Nocturnal frost occurs frequently on the high plateau during the months of June and July.

4.6 Pedology

The simplified soil map in Figure 9 gives a panoramic view of the geographic distribution and representativeness of the larger soil types in the Cunene Basin. The classification that was adopted is the one used by the Mission for Pedology in Angola and Mozambique (MPAM) and by the Research Center for Tropical Pedology (CEPT), and the corresponding classification as used by the FAO/UNESCO is noted in parentheses. The various types of soils that are represented can be classified in eight pedologic categories with similar characteristics. They correspond to the pedologic sequence of the legend of the simplified map, namely: Alluvial Soils – Soils of fluvial origin that identify the low-water levels along the main water lines, with significant representativeness in the semi-arid zone of the Cunene River Basin. These are scantily evolved soils, which are either uniform or heterogeneous as far as their texture is concerned, depending on the composition and distribution of the sedimentary materials and which tend to be fine in the humid areas and coarser or average in the drier zones.

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Alluvial soils (Fluviosoils)………….1 Aridico-tropic soils (Lixisoils).....5 Lithosoils (Leptosoils)……….……..2 Halo-aridic soils (Solonetz)...... 6 Psammitic soils (Arenosoils)...... 3 Fersialitic soils (Acrisoils)...... 7 Clay (Vertisoils)...... 4 Ferralitic soils (Ferrosoils)...... 8

Figure 9 – Dominant soil types in the Cunene River Basin

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Litho-soils – In the arid zone, coincident with the lower Cunene Basin, the litho- soils are widely found, and generally with an accentuated stoniness. These are soils that are not much evolved, of moderate thickness, and this durable hard rock occurs at depths of less than 30cm.

Psammitic soils – Corresponding to soils with a coarse texture, loose, with a reduced proportion of fines, with a tendency to increase in size with increased depth, permeable and very thick. The psammitic soils occupy large surfaces in the central Cunene Basin, corresponding with the sandy deposits from the Kalahari, and are superficially pale grey and colored in the subsoil, but often yellowish or orangey.

Clays – Heavy clay soils, with a strongly sialithic clay, with effective expandability and broad fracturing during the dry season, rather tacky and with notable plasticity, extremely hard when dry and which present a characteristic micro-relief of the gilgai type. These soils are well represented in the central basin of the Cunene, corresponding with the gabbro-anoththosites, and are often associated with rocky outcrops and in the Caculavar valley, involving both the low-water level (black alluvial clay) and the adjacent slopes.

Arid tropical soils – These are soils that have evolved under normal dry climatic conditions (arid and semi-arid), with fine fractures and dominated by sialithic clay, with a varying proportion of mineral reserves, strongly saturated in the lower layers and a high capacity for cationic exchange, with – at varying depths – horizons of accumulation of calcium or gypsum. It has a pale-grey coloring and, less often, grayish-red and has in its circumscribed incidence, in the semi-arid zone, the region that is commonly known as the Lower Cunene, which is characteristically enclosed by the valleys of the Cunene and the Caculavar.

Halo-aridic soils – Soils that, whilst they integrate themselves taxonomically into the category of aridic tropical soils, are recorded separately in view of their specific characteristics as regards their occurrence in sodic or sodic-saline horizons at a greater or lesser depth, which determine the conditions that are rather favorable to the silting thereof as no specific techniques are adopted for their use. The presence of these soils

Page 63/214 LNEC – Proc.605/1/11926 has particular significance in the Lower Cunene, corresponding to badly drained surfaces that become saturated with water during the rainy season, and which are mostly only eliminated by evaporation, which results from the occurrence of impermeable or compact horizons at inconvenient depths.

Fersaliltic [?] soils – These are soils of normal occurrence in the transitional belt between dry and humid climates, in general with an average texture, with variable content as far as alterable minerals are concerned, with high rates of saturation in the lower layers and in cationic exchange, with moderate to slow permeability and a good capacity for usable water. These soils occur with a significant degree in the northern part and NW of the central basin of the Cunene, defining a belt that surrounds or separates the psammitic soils from the ferralitic [containing iron?] soils.

Ferralitic [?] soils – The lower section of the Upper Cunene is essentially identified by ferralitic soils, or by mineral soils with fine or medium/fine textures, chromic, made up by caulinic minerals, iron oxides and aluminium oxides, with weak structuring, brittle, with low to very low rates of saturation and cationic exchange in their bases, with frequent occurrence of dispersed laterite concentrations or concentrated in hard horizons or benches [zones/layers/bands], at variable depths. The ferralitic soils link their presence to the basin of the Upper Cunene, with its humid climate and corresponding to the Planaltic surface at a height of above 1300/1400m.

4.7 Vegetation cover

There are 5 large phytogeographic zones in the Cunene Basin which reflect the phytoclimatic conditions of the regional environment (Figure 10).

The open forest or “panda” woods make up the type of vegetal ensemble that identifies, from an ecologic point of view, with the wet tropical climate in that a well- marked alternation between rainy and dry seasons takes place, which is characterized by a forest cover with the species Brachystigia, Isoberlinea and Julbernardia. The vast degraded areas in the open forest zone are the result of agricultural occupation of the land, and one comes across several savannized communities, from the savannah to bushland with savannah-coppices.

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PHYTOGEOGRAPHIC ZONES Open forest (mata de panda) and savannah with shrubs……..1 Dense dry forest (mata de muiumba) and thick shrubland……2 Wood and savannahs of the mutati type………………………..3 Steppe and shrubs of the sub-desert belt……………………….4 Steppe of the desert belt…………………………………………..5

Figure 10 – Phytogeographic zones in the Cunene River Basin

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The dense and dry forest is a vegetal community that corresponds to the sub- humid dry and semi-arid climatic zones, and it covers deep sandy soil surfaces that are naturally well-drained. The wood species Baikiaea plurijuga characterizes the formation that is regionally known by the name of “muiumba” woods, that is generally rather degraded due to human intervention, and its replacement by communities of a darker and denser nature with a variety of components, with a various acacias and species like Croton, Combretum, Grewria and others.

Formations of “mutiati” (Colophospermum mopane) occupy extensive surfaces in the semi-arid zone and correspond to surfaces with inadequate drainage and that become saturated with water during the rainy season.

The “mutati” is a tree or shrub species that characterizes this formation, sometimes occurring in high density populations and in other instances associated to other tree species, whereby the Spirostachys africana and Acacia, Combretum and Commiphora are prominent. This type of formation reflects the conditioning in as far as the presence of sodic or sodic/saline horizons are concerned, just as the coppices that are composed of various tree species are characteristic. On the other hand, the clays and clay-type soils in general in topographic localizations with water saturation under rainy conditions, they generally are linked to coppices or woody savannahs, or to extreme shrub formations.

In the dry zone the vegetation takes xerophytic facets that become more pronounced in proportion with the influence of the coastal fringe, constituting a typical community of a steppe with shrubs. The woody elements are scrawny and somewhat dispersed and consist mainly of species like Acacia, Commiphora, Combretum, Boscia, Croton, Terminalia, etc. The herbaceous cover, in tufts and rather sparse, are from the domain of the graminae and the species Aristida and Eragrostis are represented.

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NATURAL PASTURE RESOURCES TYPES OF HERBACEOUS COVER Zones with acrid pasturage …….1 Zones with mixed pasturage……2 Zones with sweet pasturage……3

Figure 11 – Natural pasturage resources in the Cunene River Basin

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AGRO-ECONOMIC ZONES Millet-growing……………………….……………..….…..1 Millet and massambala…………………….…..………..2 Massambala and massango and cattle-growing……..3 Cattle-growing and reduced agriculture (massango)...4 Reduced cattle-growing …………………………………5

Figure 12 – Agro-economic zones in the Cunene River Basin

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In the desert belt the shrub stratum is of a steppe-like formation, disperse and low-growing, reflecting the strong xerophytism that is accentuated by succulents and prostrated plants, whilst the grass stratum becomes sparse, non-diversified and ephemeral.

In Figure 11 one may find the various types of herbaceous covers that are reflected in the hydrographic basin of the Cunene, and the geographic distribution that defines the natural potential for exploitation by means of cattle-breeding. The main characteristics that differentiate the three types that were taken into account are:

The zone with acrid pastures corresponds to a large degree with the basin of the Upper Cunene, reflecting the conditions of a hot and humid climate of the rainy season that provides significant vegetative development of the herbaceous cover, dominated by graminae of the species Hyparrhenia and that are associated with other higher-growing types of grass, especially Andropogon. In the dry season, the dry grass cover becomes hard and is subject to burning, after which it sprouts again; it is during the few months of this phase that the cattle can benefit from it.

The zone of mixed pasture corresponds to a large degree to the sub-humid humid humid and sub-humid dry climates, in that the herbaceous cover – like in the previous case – is dense and grows tall, and is of a varied tree composition with a higher forage value, whereby the species of Panicum, Heteropogon, Digitaria, Chloris, Setaria and others stand out. The diversity of the grass species and their forage value, keeping up good conditions for consumption throughout the year, make this a zone rather favorable for cattle-breeding purposes, which might turn out to be rather lucrative, and it also provides adequate conditions for cattle-management and grazing.

The zone with sweet pastures combines the dry and semi-arid climatic zones, those with marked atmospheric and soil dryness during the long dry season. The herbaceous cover is dominated by types of grass that are edible throughout the year and that have high forage values, in particular in the semi-arid zone, which is why it is of great interest for traditional cattle-breeding which is based on grazing. In the spaces

Page 69/214 LNEC – Proc.605/1/11926 where there is no or little population, cattle-breeding operations might be introduced that would be based on a rational distribution of the natural grazing resources.

The climatic and pedologic characteristics determine the types of rural occupation and land use that are reflected in the lifestyle of the population. It is thus that, along the Cunene River, from its source towards its mouth (Figure 12) a succession of different agrarian structures can be noted, that are not only translated into the condition of the environment but also into the way in which the populations have managed to prevail over them. As far as the Cunene Basin is concerned and from a global analysis it transpires mainly that one goes from a situation of agricultural utilization without irrigation, based on the planting of millet, to another, where the pastoral activity will gain in importance until it reaches almost exclusive characteristics at the lower end[ of the basin].

In this manner, Zone 1, with its non-irrigated millet crop growing with, to a lesser degree, associated plantings of beans and sweet potato, corresponds in essence to the basin of the Upper Cunene and the humid climatic zone. There is but little cattle- breeding, with the cattle being used mainly for tilling and for transport of produce.

In Zone 2 we note millet and sorghum crop growing, the agricultural activity is still not making use of irrigation; however, it already slots into the central Cunene Basin. In this sub-humid humid zone the cattle starts to gain some importance, however, without constituting an economic factor of relevance.

In agricultural Zone 3, cattle-breeding already becomes an economic factor with some importance, but the agricultural activity that is based on the growing of crops like sorghum and massango – cereals that, as they are more resistant to drought, tend to dethrone millet – still remains linked to the fulfillment of alimentary needs and still keeps its primacy status. One could say that, in this area of the central Cunene Basin with its sub-humid dry climate, smaller mixed explorations (both crop-growing and cattle- breeding) characterize the rural structure of this zone.

Agro-economic Zone 4 integrates what is commonly called the region of the Lower Cunene; it is characteristically a cattle-breeding area, traditionally linked to the life

Page 70/214 LNEC – Proc.605/1/11926 of nomadic pastoral people, who trek with their herds in accordance with the distribution of grazing-lands and the watering-points for their cattle, and according to the seasons. The agricultural activity is rather reduced, mostly limited to small land tracts that are adjacent to the homes, mainly massango as this is more drought-resistant than any other crop, and with the harvest being for the exclusive use of the family.

Finally, there is agro-economic Zone 5, which corresponds to the lower Cunene Basin and which is part of the arid climatic zone. The severe limitations and adversity of the environment considerably reduce the potential for cattle-breeding, confining it to certain localities that are better endowed, whilst the agricultural activity totally loses its importance.

One might also define the area between upstream from Mulundo and Calueque according to the following vegetation zonings:  Etunda: dry forest, dominated by the occurrence of Baikea, to which other tree and shrub species like Combretum, Commiphora, Pterocarpus and Ricionendrum are associated, in addition to some graminae like for instance the genus Aristida.  Etunda-Kiteta: a formation with spinous woodland, made up of dense spinous shrub vegetation that is quasi impenetrable, with a decrease in herbaceous cover that could be used for grazing.  Epia-Etunda: open dry forest that provides the transition between the zones of Etunda and the more savannah-type zones, like the Chanas, Evandas and Muenhes. This mainly emerges in soils that are used for agriculture and that are characterized by tree species of the genii Adansonia, Carissa, Acacia, Combretum, Ricinodendrum, amongst others.  Muenhe: an association of open dry woodland on arid soils and soils with inadequate drainage. It encircles the regions of Etunda and Epia-Etunda and it is characterized by the tree species Colosphospernum mopane. It also has a shrub- and herbaceous stratum made up by Eragrostis and Aristida.  Tchana or Chana [Oshana]: typical savannah-type formation with scattered shrubs of the same species as those that occur in the Muenhe;

Page 71/214 LNEC – Proc.605/1/11926 the dominating grassy species also are Eragrostis and Aristida. It occurs in altitudes that are lower than those of the Muenhe and are subject to periodic flooding.  Lwano: these are areas that also have inadequate drainage, which can be found in the area of Calueque; they are covered by quasi pure formations of Colophospernum mopane. The herbaceous stratum – that has little resistance to grazing – is well-represented, and one may find among various genii the Eragrostis and Aristida that were already mentioned above.  Mulola: zones with wide valleys where impermanent rivers flow, covered with some of the vegetation that is typical for the Evandas, like Kirkia and Oriza. Just like the Evandas, these are the basic zones for local grazing.  Evanda: alluvial plains that are periodically flooded by the Cunene, Calonga and Caculuvar Rivers. Here the tree species Acacia, Diospyros and other vegetation, like Oriza, Vetiveria and Syzygium are represented.  Etala: permanent pools that can be found in the Evandas or in areas that are temporarily flooded. They have an aquatic vegetation.

4.8 Demographics and population

For the conclusion of the work it is necessary to point out that there were difficulties to obtain information on a country that has lived through major political turbulence, a civil war that lasted more than twenty years, and that was followed by an equally chaotic period during the war of independence that started in the Sixties. The reflection of this politico-military conflict in terms of social and human terms continue to be felt all over the territory, be it with varying intensity. Southern Angola did not escape the devastating consequences of the conflict which saw its repercussions in the destruction of basic infrastructures for the development and support of the people‟s lives, partial destruction of production resources, forced removal of the resident populations as well as the mobilization of a large part of the men – young and older – in order to fight. All this has had an impact on the demographic and social structure of the region and is largely disregarded when the political and administrative structures are defined that structure the existence of a State to the modern acceptance and validation that is to be acknowledged, and, finally, the world-wide instability that has very negative

Page 72/214 LNEC – Proc.605/1/11926 consequences, in particular in as far as the living-conditions of the resident population is concerned.

In order to have an idea of the deterioration in living-conditions in Angola, one may consult the evolution that is recorded in the index of human development. We refer to an indicator that is used by the United Nations and that combines indicators of national gross product, life expectancy and educational levels that have been achieved, in order to obtain a composite average image of human progress. With all relativity that such a type of indicator comprises, its use for the purposes of global and international comparison does not seem unbalanced to us. The data for 1992 express a scope that varies between a minimum (0,052) that corresponds to Guinea, and a maximum (0,982) that corresponds to Canada. Angola represented the rating of 0,304 in the middle of the Eighties, with a world-wide ranking of 139 (out of [participating] 160 countries). In 1990 the value of this indicator decreased to 0,169, even if Angola retained its relative ranking. Two years later, by the year 1992, the indicator rose to 0,291 but its relative rating dropped to 160 (out of a total of 174 countries).

This precarious situation has given rise to a significant volume of international aid, which was, however, conditioned by the war. Like the other providers of aid, the European Community has focused its efforts on humanitarian relief and on rehabilitation, with the majority of these development projects being long-term.

Some sectors of economic activities in Angola, that were considered to be of vital importance for its development, have been favored by the Community‟s relief efforts as regards direct help to the economy. In this respect the fishing industry, the reanimation of industrial and agricultural activity through the concession of funds for imports of production commodities, the rehabilitation of infrastructures and in particular basic sanitation, health and roads [were targeted].

The sectors of basic sanitation and of the supply of drinking-water to the people should be particularly mentioned at this point, because of the fact that it they are directly related to the plan for the development of these sectors in Southern Angola (the.

Page 73/214 LNEC – Proc.605/1/11926 Table 1 – Population of the municipal areas that make up the Basin, by province

Page 74/214 LNEC – Proc.605/1/11926 collection of underground water), and also because they are considered paradigmatic for the state of infrastructural degradation in which the country finds itself. The Report on National Evaluation (1991), which was commissioned within the scope of the International Decade for Potable Water and Sanitation, is however quite critical about the low level of implementation of the plan, with just 20% of the rural population benefiting from the improved supply, with the lack of maintenance contributing to the low extent of performance.

As there are now documents available that relate to the administrative realities of the territory that comprises the Basin, it became necessary to cross-reference information that was obtained from a variety of sources and that allowed to glean an approximation to reality but that might contain some errors.

The indicators on the size of the population refer to an assessment that was made for the year 1990. The Cunene River Basin comprises 22 municipalities in 4 provinces (Huíla, Huambo, Cunene and Namibe). The province of Huíla is most represented with 12 of its municipalities (see Table 1 and Figure 13), which corresponds to a population of 900.024 inhabitants, 45,6% of the population of the Basin and 89,9% of the population of the province. Huambo has 5 of its municipalities and 63,9% of the population of the Province that are situated in the Basin. The Cunene with 4 of its 6 municipalities and an effective 188.871 people represents 9,6% of the Basin and 54% of the Province. And finally, the Province of Namibe with just a negligible contribution in the southern part [of the Basin] with the municipality of Tombua that is included in the Basin, contributing to the population by an estimated 1000 inhabitants.

Note: because of its insignificant contribution to the population, this graph does not make mention of the Province of Namibe. Figure 13 – Contribution of the Provinces to the total population of the Cunene Basin

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Capital de Província = Capital of Province Sedes de município = Municipalities

Figure 14 – Geographical delimitation of the Cunene Basin, by municipal areas

Page 76/214 LNEC – Proc.605/1/11926 It is thus estimated that the population of the Cunene River Basin would be 1.975.429 inhabitants, which corresponds to a population density of 21,4 inhabitants per km2, see Figure 14. Density varies in Southern Angola between 40,3 inhabitants per km2 in Huambo to 1,7 in Namibe. These values translate the demographic diversity of the territory that is the subject of this analysis, and that corresponds to the cultural and ecological diversity that is embraced by the Cunene River Basin.

The values of the proportional contribution by each province to the population volume of the Cunene River Basin (see Figure 13) have been taken with the coefficients for the determination of weighted averages that had to be calculated for the Basin, be it as regards the population volumes, be it for structures.

The variation in population density is strongly associated to the types of social organization and to the economic activity of the population that resides in the Basin, whereby it is possible to identify three major population patterns: a) the urban population, that includes in some cases areas that might be treated as suburban; b) the agricultural population, with its rather divergent profiles but still with some degree of concentration as far as their habitats and numbers are concerned, around the agricultural exploitations and that provide the development of some commercial activity; c) the pastoral population that is mainly grouped in scattered family units, of a nomadic nature (semi-nomadic to nomadic), associated to the economic activity of subsistence farming.

The concentration of the population in urban centers of medium to large size in Angola has varied significantly over the recent years, even if not always in the sense of a linear or exponential increase – with the most noteworthy example of exponential increase [occurring] in Luanda. In the context of the war, the urban centers have an increased security factor, as happened in the south of the country (the increase in the town of Lubango has become very marked because of this reason), for the reason that increased military hostility corresponded to an influx of people into the cities, not necessarily from the communes, municipalities or even the surrounding provinces, whereby the reversal of this correlation is somewhat true [took place to some extent] but not always to the same degree. However, when military action took place within an urban perimeter (be it from the outside to the inside, through bombardments, be it within

Page 77/214 LNEC – Proc.605/1/11926 the town), as in the case of Huambo about seven years ago, it might have become more dangerous to stay inside [the perimeter of the town]. These facts that would destabilize the urban population made it impossible to estimate the actual volume of the population with some degree of accuracy. However, retrospectively it might be said that, at the beginning of the Nineties, the city of Huambo had a population of around 290.000 inhabitants, and the city of Lubango approximately 163.000. These are the two most important urban centers in the region.

From the point of view of demographic structures, the difficulties to estimate the population concentration according to age or sex would turn out to be major as compared to those encountered with regard to the [overall] volume, because of the fact that these have to be added to those that result from isolated portions of information, and that would always require a solid base by census. On the other hand, in view of the significant variations of the demographic structures as far as age groups and the balance between genders are concerned – and this is exacerbated by the fact that the populations are subject to phenomena like an increased differential mortality or the mobilization of the men for military service – it will be indispensable to carry out censuses with a more restricted geographical incidence.

The lack of information – the data that are available is not up-to-date and rather dispersed, in view of the fact that the last censuses took place around the middle of the Eighties and did not even have partial coverage – required consideration, once again, of a geographic unit that could be used for orientation purposes and that was more trustworthy (the province). That is why we proceeded to the characterization of the demographic structures for the year 1990 in the three provinces that are part of the Basin (see Figure 15), defining a typical structure for this geographical unit and the repercussions of a weighed distribution by age groups for the population size that had previously been assessed (and that was recorded to be 1.975.429 inhabitants), in agreement with the proportional representation of the three provinces.

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Figure 15 – Demographic structures of the provinces of Huambo, Huíla and Cunene in the year 1990 The comparison between the demographic structures of the three provinces reveals a rather strong similitude between Huambo and Huíla, whereby it was confirmed that the structure of the Cunene, whilst it was also rather young, presented lower values until the age of 10 years, and slightly higher ones for the last [highest] age groups.

As far as the structure of the Basin is concerned, it is overwhelmingly influenced by the structures of the two most populous provinces and one may conclude that it is rather young, as about 50% of the population is younger than 15 years. 90% of the population is below 40 years of age, as the percentage of those who are older than 55 years was reduced (the age from which – in view of the average life expectancy in Angola – a person is already considered to be elderly).

If the analysis would only concentrate on the rural population, and in concurrence with a study that was carried out in the rural areas of the provinces of Huambo, Huíla, Cunene and Namibe, the average age would be between 21 and 23 years (this is considered to be high), whilst a imbalance is noted in the gender/age structure, with a clear predominance of women. The authors of the said study attribute this to the exodus of more youngsters towards the city and to military service conscription.

The families are usually of an extended nature, with an average of eight people per family and about 20% of the heads of family with a second wife. The birthrate is of around 6 children per woman at the end of her reproductive life. Infant mortality is of 170

Page 79/214 LNEC – Proc.605/1/11926 per thousand and the life expectancy at birth (feminine gender) is of 51,5 years. The study concluded that, in parallel with the strong rural exodus, there is an intense inter- rural migratory movement.

These rather intense movements do not allow putting forward any current data on the demographic structure that would have any degree of exactitude in as far as the ratio by gender is concerned. Because of the selectivity of military conscription and of the incidence of civil casualties, but above all because of the reaction by the population to the various war-related focal points that flare up increasingly in various regions, strong variations in the population [structures] that reside in this or that municipality or agglomeration and in particular in the composition by age or gender result in compromising the interest that a projection in accordance with these two structures (age and gender) could have together, if no additional data becomes available.

It is perhaps important to take the data on the number of displaced persons per province into account, and this as a point of reference for the evaluation of the perturbations that have been mentioned; however, it will not be possible to estimate how many of these happen to be in the Cunene River Basin. Therefore, according to UNICEF, there were around 94.000 displaced people in the Huambo Province during 1990, 61,3% of whom during a period of less than 6 months (the date of the assessment is available). The incidence of this number of displaced people per municipality is rather varied, with an enormous concentration in the municipalities of Huambo and Caála that are situated in the Cunene River Basin (45,3% of the total number of displaced people). In Huíla Province the total number of displaced people amounted to around 64.000, here with a major incidence in the municipal areas of Lubango, Caluquembe, Quipungo and Chipindo, that embraced around 60,5% of the total number of displaced people in the province. There are no data available for the Cunene Province at that date (1990). It may be concluded that there are probably a high number of refugees in the Basin, possibly exceeding 100.000.

The political and military instability in the region, associated with a number of organizational inadequacies, have left the sector of sanitary and educational installations particularly impaired, not to say totally incapable to respond to the minimum

Page 80/214 LNEC – Proc.605/1/11926 requirements of the population, and as a result of the above-mentioned instability these facilities are considered to be priorities [desirable].

For the same reasons it was noted that there is a total absence or scarcity of documentary records that raise great doubt, furthermore, as the authors wish to put on record. The most recent information dates back to 1990 and covers the provinces of the Basin in a rather lopsided manner. It is clear that a part of the region has since that date perhaps suffered its major military conflict, which has worsened the effectiveness of the existing infrastructures to a radical degree, and which has weakened the population – possibly to a point of exhaustion – with its illnesses, epidemics, hunger and forced displacements that were brought about by this “Civil War”.

However, it is beyond doubt that the situation needs to be considered as being extremely precarious, as was already noted in 1990 by some of the sources and reports that were mentioned above. Thus, during 1990 and in agreement with UNICEF, a large part of the infrastructures were noted as either not operational or with seriously compromised functioning in the provinces that comprise the Cunene River Basin. The availability of medical-sanitary services providing effective aid to the population (consultations, vaccinations, hospitalization) was limited.

The seasonal rainfall caused situations of isolation for a part of the population. There is for instance no evaluation or diagram that exists and that could indicate the areas that are vulnerable to [seasonal] rainfall and, on a second level, information on the behaviour/adaption to rainfall, as well as on the collective perception of the risks and benefits thereof.

Wood is practically the only source of energy; it is used on a daily basis without any known actions as regards reforestation.

As far as habitations are concerned, it is notable that there is a dilapidated housing structure in the urban agglomerations and quasi entirely of a traditional nature in the rural environment. It is in this context that the criteria for the quality of housing need to be defined, taking into consideration the expectations and the requirements of the target population, in particular as far as domestic use of water is concerned.

Page 81/214 LNEC – Proc.605/1/11926 In conclusion, a note regarding the cultural characteristics of the population groups in the Cunene Basin. The people who live in the Basin have particularities that cannot be ignored when establishing any plan that aims at the promotion of change [moving]. It is an area that needs to be considered in detail and also as far as the sociological preoccupations of the previous teams are concerned whose work on the subject of the Cunene provide an important contribution, as do studies that have been made by the Portuguese Anthropology [Team] in the region.

5. EVALUATION OF WATER RESOURCES

5.1 Surface Water

5.1.1 Hydro-meteorological information, rainfall and river capacities

Data from 87 pluviometric stations were available. Figure 16 depicts the sites of these rain-gauges. The analysis of this figure shows that the majority of stations that existed at the time were situated in the source basin of the right-bank tributaries of the Cunene River. Therefore, the cover of the left bank of the river as well as the section downstream on both sides is rather inadequate. On the other hand, around 30% of the rain-gauges are situated outside of the basin, even if they are useful for the study of precipitation within the basin as they are located relatively close to the boundary line of the basin.

It is noted that stations exist where the records were started in 1945. However, with some exceptions, the registers contain many shortcomings. Many of the rain-gauge stations are also – or used to be – climatologic and meteorological stations, where other variables are recorded like the wind, evapotranspiration, temperatures, etc.

Based on existing data, individual files were made for each post or station. Each file contains the monthly rate of precipitation, the average for each month, variation patterns and the number of years of each monthly series, as well as the relevant annual values.

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Estação Meteorológica = meteorological station Estação Climatológica = climatographic station Posto Udométrico = pluviometric station Limite Bacia Hidrográfica = border of hydrographic station Curso de Água = water line Capital de Província = provincial capital Fronteira = border

Figure 16 – Pluviometric, climatographic and meteorological stations.

Page 83/214 LNEC – Proc.605/1/11926 It was found that the station with the highest annual rainfall measured 1618mm, with a variation pattern of 413mm, around 26% of the average. The station with the lowest rainfall had 422mm, with a variation pattern of 167mm, around 40% of the average. The number of years on which the averages are based has a maximum of 25 years, whilst the majority [of stations] are younger than 10 years.

Data was found from 21 hydrometric stations that ceased operations in 1974 and that had periods of registration that were very short and rather incomplete. Of [these] 21 stations, 14 were situated on the Cunene River, two on the Calai, and on each on the tributaries Cuando, Catapi, Nene, Colui and Caculavar. Figure 17 shows the stations in question. An analysis of this figure reveals that the stations cover the Cunene River basin in a reasonable manner. Table 2 depicts the areas of the basins that are drained by the hydrometric stations. It is noted that the last hydrometric station on the Cunene River, the one at Chitato, covers around 81% of the area of the basin.

It was also noted that the registers were only started during 1963, that they were known just until the year 1971, with the exception of the station at Ruacana where registers exist up until 1976. The volumes in that station were measured by South Africa. With some exceptions, the registers contain many shortcomings.

Based on the existing data, annual files were established for each station, with the rates of daily volumes, the average for each month, the variation patterns, all [expressed] in m3/s, and the number of days of each monthly series, as well as the respective monthly totals of discharge in hm3. For each complete year the average daily volume was also calculated, and the [relevant] deviation pattern, as well as the total annual discharge in hm3.

Some stations only have one year[„s worth of records] with a maximum of 18 years at the Ruacana station. This station covers around 79% of the basin and its average annual volumes vary between a minimum of 78m3/s and a maximum of 344m3/s, which means with a ratio from 1 to 4,4.

It was also found that some stations downstream would show volumes that were lower than those upstream (example Matunto and Xangongo).

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Estação Hidrométrica = hydrometric station Limite Bacia Hidrográfica = border of hydrographic station Curso de Água = water line Capital de Província = provincial capital Fronteira = border

Figure 17 – Hydrometric stations

One might deduce that some values are not correct, in particular as the stations downstream present values with volumes that are lower than those upstream. However, it is necessary to note that, in addition to the errors that are inherent to any observation of volumes and that may sometimes be important from a physical point of view, such a situation with a decrease in volume downstream is plausible and can result from the existence of evaporation or an increase of the sub-superficial component of the discharge in alluvial beds.

Page 85/214 LNEC – Proc.605/1/11926 The numbering of the hydrometric stations on the Cunene River increases in a downstream direction, and when it relates to a tributary it consists of double digits, with the first number corresponding to the station of the main stream that is situated downstream from the confluence, and the second number corresponding to the numbering of the tributary, increasing in a downstream direction.

Table 2 – Areas in the hydrographic basins that drain into the hydrometric stations

5.1.2 Compilation and supplementing of missing data

In the first phase of the study of a problem it is necessary to gather fundamental knowledge on the structure of the system in order to provide a reproduction that is as faithful to reality as possible.

Page 86/214 LNEC – Proc.605/1/11926 During this study, the question of the missing data on discharge levels at the various hydrometric stations arose instantly. This was because the lack of available measurements existed either at a daily and monthly level or sometimes even the yearly figures were missing for some hydrometric stations.

The methodology that was embraced for the supplementing of missing discharge data was the implementation of multiple-regression techniques on the discharge rates of the various hydrometric stations. The correlations that were obtained took the geographic situation of the various stations into account in order to physically corroborate the mathematical relationships that were obtained.

Furthermore, regressions may have been used that included the rainfall data for the various stations, whereby this work was seen with a rather pessimistic slant as the rainfall data also contained numerous shortcomings.

Based on the previously mentioned aspects regression lines were established and the study thereof followed the phases that were schematized in Figure 18, and that would describe:

1. Choice between the discretionary use of historic data, at a daily or monthly level, as a basis for regression: if the missing data would correspond to an entire month, or even several months, it would not make sense to establish a regression on a daily basis, and a regression of monthly volumes would be selected. On the other hand, if the missing data would relate to just a couple of days of each month, an estimate of the missing daily values would be chosen. 2. Selection of data on the independent variables for the regression. In the case of the option for a monthly regression, these variables would be the monthly discharge of the preceding, current and future years. In the case of the option for a daily regression, the independent variables would be the existing daily data for the month containing gaps, and the daily discharge of the preceding and following months. 3. Determination of the statistical correlation between the discharge data at the station that showed a lack of data, and the discharge data of the other stations.

Page 87/214 LNEC – Proc.605/1/11926 4. Validation of the most significant statistical correlations by means of the geographical situation of the stations that were correlated or, if the stations were located close to each other, if they were far away from each other, if they had similar climatic conditions that would have an influence. If there were several stations of equal value, the one that had the most factors or observations in common with the station that had to be assessed was chosen. 5. Selection of simple or multiple regression (as adequate for each case), taking into account that the any new variable would only be included if it was of statistical significance.

[block 1= choice of merit of data] [block 2 = Determination of statistical correlation of data with all remaining stations] [block 3 = Confirmation of independent variables on the basis of the geography] [block 4 = Determination of the statistical regression and validation]

Figure 18 – Diagram of the procedure to complete the data for each of the hydrometric stations

For the calculation of the regressions the program STATISTICAtm was used. The technique that was used for the selection of the best regression was the stepwise regression. For explanation purposes we present some of the regressions that were used.

For the station of Lucunde a multiple regression was obtained by making use of the data for Jamba-ia-Oma (immediately upstream) and Catapi, that may be further

Page 88/214 LNEC – Proc.605/1/11926 away but is situated at the same bank of the river and does not have major climatic differences. With 40 observations a regression with r2 = 0,9335 was obtained,

For the station at Matala, the first problems that were encountered concerned the historic data, as the discharge volumes of this station in certain months are higher than those of Folgares (downstream), a difference that might just be explained by the large distance between the stations, in conjunction with the immediacy of the dry season when evaporation might be considerable.

After testing various independent variables for the purposes of the regression, for stations upstream or for Folgares [which is situated] downstream, two better regressions were selected, the one being a multiple regression with r2 = 0,9861 and another, simple linear regression with the station of Matala, with 120 observations that resulted in a regression with r2 = 0,9734.

In spite of having succeeded to reach a better adjustment factor as regards the use of multiple regression, it was decided to opt for the simple regression, as it was not only based on a far larger number of significant observations than the first assessment, the rate of the original ordinate was not significant with a level of 95% once two explicative variables were employed.

As far as Gove is concerned, the fact that there are two measuring stations with this name (Gove I and Gove II), that never have operated in conjunction, triggered initially the research on its geographic position in order to perfectly understand the climatic conditions and if these would be identical for both [stations]. Because of the fact that the surface of the basin is smaller for Gove I (97,58% of the hydrographic basin of the Gove II station), the rates of discharge at Gove II were multiplied by this constant [factor] in order to obtain a single series of data.

It was noted that a strong correlation existed between the monthly values of these two stations and those at Jamba-ia-Oma, which is situated immediately downstream.

Page 89/214 LNEC – Proc.605/1/11926 In this way it would be possible to plot a regression with that station but it did not produce satisfactory results, and important seasonal variations and a pronounced reduction of the values from Jamba-ia-Oma were discovered, which involved precisely the missing months for Gove. As there was a pronounced reduction during that period, followed by a slight increase of the values for Jamba-ia-Oma, values were computed manually by means of projections [lines] that should represent this performance. For the minimum value to be attained at Gove a value that was in proportion with the size of its basin was selected, as this was identical to what was observed for Jamba-ia-Oma for the same temporal instance.

It then became pertinent to observe that the remaining gaps in the data were filled, using [simple or] multiple methods of regression, as considered to be appropriate. Whether on a daily or monthly basis, the justified variables always exceeded 82 for the purposes of supplementing missing data.

5.1.3 Management of artificial drainage systems

Simulation is a much-used technique in the analysis of water resource systems, because of its capacity to analyze any system, allowing the evaluation of its performance on the basis of well-defined operational policies.

The precision of the results of the simulation studies (for example, the size of intervals of certainty that was obtained) depends primarily on the input of the series of stochastic variables that are used for the simulation model. As, in the vast majority of cases, the historic series are relatively short, the necessity to obtain synthetic series emerges that can be used as a basis for simulated studies of hydrographic basins.

The management of synthetic series is achieved by having recourse to a stochastic model that has to faithfully represent the characteristics of allocation of the historic data. For the final analysis the model that is reproduced should reflect a marginal distribution of the seasonal values and a marginal distribution of the annual values.

Page 90/214 LNEC – Proc.605/1/11926 The first step in the construction of a statistical model for discharge management is to extract the elemental information on the combined distribution of discharges at different sites and over different periods, from the historic series of discharges.

As a synthetic model for discharge management cannot preserve all correlations that exist between the hydrologic data without surcharging it, to the detriment of a high number of parameters that would need to be assessed, the necessity arises to reduce the number of the correlations that one has to retain.

The statistical recording of the synthetic discharges is normally made on the basis of an assessment of the moments, in order to reproduce them similar to the historic ones. A model of discharges is often said to reproduce the historic discharges in a historic manner if this model manages series of discharges with statistics that include historic data, like for instance: average, variable or deviation patterns, coefficients for asymmetry or autocorrelation and/or cross-correlations.

Once the parameters of the model that optimally represents the historic discharges in the Cunene River hydrographic basin have been determined, synthetic series of discharges were generated.

For that purpose groups, with five hundred discharge sequences were produced, with an equal number of years as the historic data contained, in order to verify the accuracy of the results that were obtained. Using the module Display Unit of the SPIGOT program (a stochastic model for the generation of synthetic sequences), it was possible to evaluate the differences of the average values of the generated series and of the historical series, as well as the deviation patterns of same. In the following Figure 19 the graphs of the differences that were obtained for three hydrometric stations (Gove, Jamba-ia-Oma and Matala) are shown as an example.

The differences of the various deviation- and historical patterns have a certain tendency towards the negative, or the deviation pattern of the generated series has a tendency to be less than the historical one; however, they are of the same scale as the historical values. The random quality of the series of synthetic discharges is not affected by this.

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Figure 19 – Comparison of averages and deviation patterns of compiled and historic values [for Gove, Matala and Jamba-ia-Oma Dams]

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To recapitulate, it was discovered that, from the generation of synthetic discharge series for the Upper and Central Cunene the following conclusions could be drawn:

- The difference between the average annual historic deficits and the average generated annual deficits is small, taking the deviation pattern for this statistic into account. The same is true for the deviation pattern of these deficits. - The series of generated discharges present more marked drought characteristics, and the accumulated annual deficits are higher than the historic ones (the historic values seem closer to the average of the generated ones and present smaller average values). The model for generation that was encountered is so to say a pessimistic one, when compared to existent data. Furthermore, such characteristics were revealed to be favorable for the assured outcome of the conclusions, seeing that the main preoccupation of the study for a system for hydro-electric supply was to obtain the maximum guaranteed value in electricity.

5.1.4 Water Resources in the Lower Cunene Area

The evaluation of available water of the Cunene River has its origin and development in the vicinity of the frontier between Angola and Namibia.

The first assessments would have been attributable to Francis Kanthack, the former Director of Irrigation of South Africa, who, in 1920, carried out measurements for the study of the demarcation of the border.

The second assessments emerge from the follow-up to the Cape Town Accord, dated 1 July 1926, where it was set down that “the use of the waters of the Cunene, at Ruacana, is shared between the Government of the Republic and the Government of the South African Union”, in its capacity as mandatory authority for Southwest Africa. The Technical Commission that was created by the Cape Town Accord consisted of: Hudson Spence, of the Directorate for Irrigation of South Africa, and Colonel Roma Machado on behalf of the Portuguese Government. In spite of the fact that the measurements that the

Page 93/214 LNEC – Proc.605/1/11926 two members of the technical commission made portrayed the dry season of 1927, both [also] presented monthly estimates for the entire year of 1927.

With the exception of a questionable assessment that was made by L.A. Mackenzie (Director for Irrigation of South Africa) and who estimated the volume at Ruacana on 1 August 1945 to be between 2000 and 3000 cubic feet per second (around 57 and 85 m3/s), the latest historical measurings (before the decade of the Sixties) that were known were those made by the Mission to Southern Angola, which was lead by Eng. Trigo de Morais.

The objective of that Mission was to proceed “to study, or to lay the groundwork for studies, on the supply of the waters of the Cunene at the border with Southwest Africa, in particular in order to define the possibility of irrigation of the adjacent territory, the production of electricity that would allow the manufacture of fertilizer, and the resulting settlement of the European population in that economically and politically highly important zone”.

If we pay heed to the fact that the first systematic hydrometric activity in the Cunene Basin took place from 1955 onward on the section of Namuculungo, that is also close to the border, it implies that the quantification of water resources at that site are [considered to be] strategic.

From 1961 onwards some data begin to emerge on the volumes for Ruacana that, nowadays, make up a series with 36 years of data. This series, however, is not stationary and benefits from the alterations to the hydrologic regimen that occurred after the filling of the Gove Dam, at the top of the Cunene, and, because of the non-inclusion – in the registers for the years 1980 to 1984 – of the volumes that flowed over the dam wall: only the volumes that flowed through the turbines of the canal were recorded.

Thus it was noted that the Cunene Basin is situated in a region where the lack of knowledge (reflected by the insignificant amount of information in the resources of the archives of the Planning Office for the Cunene) stems from the fact that, in the Sixties, there was a concerted approach to bring any studies on the Cunene into line. This fact resulted in the concentration of the Portuguese on the area between the source basin of

Page 94/214 LNEC – Proc.605/1/11926 the river and Roçadas and the Administration of Southwest Africa [took charge of the section] between Roçadas and the Atlantic [Ocean].

The absence of relevant information on the basin of the Lower Cunene in the archives of the Planning Office for the Cunene extends even to the topography of the area that is drained on the left bank. No elements whatsoever (hydrometrical or physiographical) were supplied for that region by Namibia that would have allowed to extend the geographic scope of the analysis, and it was [therefore] decided to consider the Cunene Basin defined at Ruacana, at the border, where the famous waterfalls are situated. For this reason the entire drained area that is taken into account is on Angolan soil, and for which information exists in archives.

With a series of short registers (or homogeneously short) to identify the vulnerability of the hydraulic undertakings on the Lower Cunene to the hydrological extremes, mainly in as far as the minimum flows and the duration of flows during drought periods are concerned, various studies were undertaken that were used as an extension to the Ruacana data, based on a correlation of the flow rates that were recorded at Rundu, on the Cubango.

The distance between these two sites is more than 500km. However, because of the lack of data, it was a matter of seeing if a hypothesis for the supplementation of data with the area in question was totally inappropriate or, on the contrary, would be acceptable.

As a preferred argument, in addition to obtaining assessments with a daily resolution, it should be noted that there are similarities between the drainage areas that overlap over 300km, the imprecise altimetry of the Cuvelai Delta, and the fact that the sections for measurement (Ruacana and Rundu) are situated at practically the same latitude.

Yet the proximity of the Atlantic Ocean of the Cunene Basin, together with the ridges of the escarpment that are exposed to the effects of the sea air (that are not felt on the Cubango), determines from the start that there are higher rainfalls on the Cunene.

Page 95/214 LNEC – Proc.605/1/11926 This [phenomenon] is compensated by the deeper incision of the waterways of the Cubango that promote better „staying power‟ for the [water-]flow in times of drought.

Another study that analyzed the arcs of average duration of average daily flows at both hydrometric stations came to the same conclusion; it is here just mentioned as a basis of the geomorphology and hydrology of the region. This fact led to the attachment of a calculation artifice, which consisted of the annual correction of the forecasts with empiric data for the reposition of the configuration of the duration arc, to the regression model, i.e. amplifying factors for the maximum volumes, and reducing factors for minimum flows. These values were later compared to the monthly scale, with the results of the stochastic model PATCH that combined serial and spatial correlations between the discharges between Ruacana and Rundu and the volumes that precipitated at the Ombalanto station.

These methods for supplementing [data] are fully justifiable in regions where there is scarce basic hydrometric information, mainly when the rainfall data are also scarce and not very reliable. This is also why rainfall measurements from the Angolan territory were taken from a model of hydrologic equilibrium with a monthly resolution in order to obtain assessments of discharges at Ruacana and at other sections upstream on the Cunene River. The weighted rates of precipitation on the various sub-basins were obtained by planimetry of the isohyets that had been plotted since 1933.

Figure 20 – Variation of the weighted average on the Cunene Basin, as defined at Quiteve

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This procedure could be criticized because of the increasing number of stations that have been included in the plotting of isohyets since 1933, and that compromise the consistency of the input data for the model. As a matter of fact, the variation of the average in time (Figure 20), which was established for the basin defined at Quiteve (above the Calueque Dam), seems to corroborate this aspect.

In addition to the previous limitation of the evaluations, there is also the fact that the period of simulation is not long enough to include various drought episodes.

This study has tested a methodology to supplement the many that have already been applied, in order to obtain not only an independent evaluation of the preceding with the help of demarcation of the magnitude of the discharges, but that better identify the vulnerability and resilience of the discharges close to the border between Angola and Namibia.

Thus the first condition that this methodology had to comply with was to embrace the meteorological episodes of this century, which had been known to be extremely dry. The report of the Mission to Southern Angola includes indications on these periods, which were based on the weighted consequences that were felt in Southern Angola.

The only stations in the basin with measurements taken close to the beginning of the century were those at Huíla/Nova Lisboa. Even if the data from Huambo were less constant in time, it was decided to opt for a verification of the evolution of its oscillations around the average and for the stability thereof, by means of the two stations in question (see Figures 21 and 22).

As can be seen from Figure 21, the rainfall volumes at Huambo station do not show a stabilized average and do not synthesize the dry periods in the south of the Cunene Basin at the beginning of the Forties which were rather severe.

In spite of the fact that the two first dry spells of the century were well represented in the data from Huambo, their negative effect on the average is only reflected as the result of the non-seasonality of the average.

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Figure 21 – Evolution of precipitation in Huambo Province

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Figure 22 – Evolution of precipitation in Huíla Province

Page 99/214 LNEC – Proc.605/1/11926 Figure 23 – Synchronization and modulation between the precipitation at Huíla and the discharge at Ruacana

In addition to the confirmation [stability] of the average, the station at Huíla already produces records on the drought that are acceptable, starting with the early Forties and at the end of the Fifties (already after the Mission to Southern Angola). It is certain that it does not properly describe the two first drought periods of the century but, the fact that rainfall records were initiated one year prior to the drought, cannot give [any] indications on the same based just on the accumulation of the deviations from the average.

Figure 23 helps to reinforce this recording and the interaction between the precipitation at Huíla and the availability of water in the Cunene at close proximity of the border. This figure will also show how the recording at Ruacana ceases to be constant after the beginning of the filling of the Gove Dam.

The values at Ruacana from before 1961 were supplemented by means of regression of the volumes at Namuculungo, Figure 24.

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Figure 24 – Synchronization and regression between the discharges at Namuculungo and Ruacana

With such affinity at hand between the precipitation at Huíla and the discharge at Ruacana, one might be tempted to use a regression between both for forecasting the water resources. Such a procedure does not seem justifiable, not even at an annual level, as can be seen in Figure 25, the dispersion is very high and the number of shared years is insufficient.

Figure 25 also contains an overlay of the evaluations dated 1920 and 1927.

Figure 25 – Annual correlation between the precipitation at Huíla and the discharge at Ruacana

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In conclusion, the admission is consensual that the values from Huíla are spatially representative (not in respect of the weighted average for the basin, [which is] 20% higher at Quiteve) but in respect of the incidence of dry and humid periods. Thus the acceptance that the rainfall figures for Huíla could characterize the alternations of dry and humid periods as they are felt in the southern area of the Cunene Basin, led to an attempt to incorporate these data in a model of sequential monthly constancy. It is evident that the assessments of such a model need to be used with a grain of salt, as they incorporate some modifications in the mechanisms for the infiltration and discharge of the Thornthwaite-Mather model, in order to allow the representation of the flows at Ruacana.

The fact that the annual regression between precipitation and discharge was not accepted as valid and, in return, to have proceeded to a monthly correlation of these values does not constitute any contradiction, in view of the fact that the method for balancing uses a number of interactions between these two factors that may explain what the variables of a regression cannot explain.

Another hydrologic variable that had to be input into the model was that of the potential evapotranspiration. For this the forecasts for actual evaporation for the basin were used as defined at Quiteve (already reasonably close to the final configuration at Ruacana).

The actual evaporation rates were transformed into potential evapotranspiration by means of simple monthly factors between the average values of the first.

In view of the fact that the main benefit of the model was the reconstruction of past episodes, previous forecasts were consulted that were made for Calueque and that can be seen in Figure 26.

Aside from the fact that these consisted of assessments for many years, and, with the exception of 1920 which seems incorrect and not substantiated by various measurings if these were made on a monthly basis, there is great concurrence with the

Page 102/214 LNEC – Proc.605/1/11926 evaluations that were made by Colonel Roma Machado for the entire year, and with those established by Spence for the dry season.

As far as the measurements by Trigo de Morais are concerned, the depletion of the aquifer has been perfectly restored and therefore the evaluations (that also represent rather low volumes) would be around 1/3 of those recorded.

In conclusion, and taking the countless approximations that were made into account, the model seems to be adequate for the reality that it is to typify. Thus the assessments that are going to be produced should, if the necessary care is taken, provide a reasonable verification to any vulnerability of the water resources close to the border.

Figure 27 portrays how the use of a series with such a scope provides much more reliable indications as far as the final section of the duration curve on the monthly flow volumes is concerned.

Again, the concurrence between the higher values for the dry season show that artifices for compensation of the maxima – as mentioned before – can be dispensed with. The non-concurrence of the minimum values is not a sign of imbalance but a better definition of the minimum values that is due to the broadening of the sample.

Figure 28 summarizes all the discharges at Ruacana, where the previous rates at the time of measurement were supplemented by the balancing method.

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Figure 26 – Validation of the model as compared to previous estimates for Calueque

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Figure 27 – Arc of duration of monthly discharge at Ruacana Figure 28 – Annual discharge at Ruacana

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5.2 Underground water

5.2.1 Description of the hydro-geological systems

The hydrographic basin of the Cunene River was divided into seven hydro- geological units, see Figure 29. Beyond the geology the climatic conditions, and in particular the rainfall and temperature condition the delimitation of the hydro-geological zones, as they are of considerable significance to the process of revitalization of the aquifers.

The Karst aquifers and the Fractured Aquifers and Ultimately Karst include carbonate lithologies from the Upper Pre-Cambrian to the Cambrian (limestone from the Meta- sediments of Espinheira and from the Chela Group), that are represented on a local basis by relatively small carbonate outcrops, that are situated between the source of the Nhalhubari and the mouth, intercalated between altered purple sedimentary deposits and cut off by the Cafema Mountains. This type of aquifer has a tendency towards high porosity and it could be at the basis of important water resources. Crystalline limestone indentations may also occur in the Metamorphic Series of Southwest, sometimes with around a hundred meters of thickness, and that could eventually be of importance for the local hydrogeology. The fragments of limestone rocks that belong to the Kalahari Sequence may also introduce themselves in this type of aquifers and be of local[ized] hydro-geologic significance. The aquifer properties of these formations are highly inconsistent both vertically and laterally and the piezometric levels reflect this variability. There seem to be two types of behavior for this type of aquifers: thus there are aquifers that are considered to be more or less extensive, with average to high permeability and with flows of 5 l/s to 10 l/s (the limestone belonging to the Leba-Tchamalindi formation) and aquifers with variable permeability, with flows of between 1 and 5 l/s (the crystalline limestone that is inserted in the Espinheira formations), which are represented in the final section of the Cunene River, from the zone to the east of the Cafema Mountains to this river‟s mouth.

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Figure 29 – Map of the aquifers in the Cunene River Basin

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Aquíferos Porosos (Quaternário e Kalahari) = Porous aquifers (Quaternary and Kalahari) Aquíferos Fracturados (Complexo Gabro-Anortosítico) = Fractured aquifers (Gabbro-Anorthosite Complex) Aquíferos Fracturados (Formações Metassedimentares) = Fractured aquifers (Metasedimentary Formations) Aquíferos Fracturados de Potencial Limitado (Rochas Graníticas e Granitóides) = Fractured aquifers of limited potential (Granite and granitoid rocks) Aquíferos Predominantemente Fracturados (Formações da Chela) = Predominantly fractured aquifers (Formations of Chela) Aquíferos Fracturados e Eventualmente Cársicos (Formação da Espinheira) = Fractured and eventually karsified aquifers (Formation of Espinheira) Aquíferos Cársicos (formações da Leba-Tchamalindi) = Karst aquifers (formations of Leba-Tchamilindi)

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The Porous Aquifers are represented by the deposits of the Quaternary and by the Kalahari Sequence, that occupy the entire central region to the east of the Cunene Basin, between Calumbinga, Chiconco, Chibemba, Cahamá, Chilau, the border with Namibia, up to the vicinity of Jamba, extending in a more or less continuous form up to the high plateau of Huambo.

These sandstone-limestone-carbonate deposits present permeability flows that vary between 2,5 and 4,5m3/h, whilst volumes of between 1,5 and 18,5m3/h can be recorded for Huíla Province. These aquifers may generally be considered as extensive, with variable permeability in depression[s] and average flow volumes that vary between 1 l/s and a maximum of 5 l/s whilst one may encounter average flows of 5m3/h for Quaternary deposits. Among these deposits, those that seem to present greater hydro- geological potential are the ones of the Lower Kalahari, as the local population opens wells in these formations and obtains water at a depth of around 5m. Most of the water that infiltrates is dissipated after the reconstitution of soil humidity and, in the dry seasons, even a large portion of the infiltrating water that has accumulated in the more favorable zones tends to be lost through evapotranspiration, this being the main reason why often aquifers do not exist even in contact with crystalline rock – in zones where the covering deposits have a thickness of between 10 and 20m. In the dry season, a large portion of the water (sometimes up to the total amount) that exists in the sandstone formations is lost through evapotranspiration.

The alluvial sand that is deposited in the oshanas are the only hydro-geological elements in the area of the Lower Cunene that offer conditions for the development of aquifers at levels of less than 30m.

Typically, the natural fluctuations of the water levels in these aquifers are in direct correlation with the total precipitation of the previous year and only the precipitations of more than 35mm have any impact on their recharging; this recharge takes mainly place along the contact between the slopes of the fossil valleys and the deposits of washed sand that could be present in the oshanas. A long period of 30 to 40 days is required to

Page 109/214 LNEC – Proc.605/1/11926 confirm the increase in levels after the first rains, which is due to the need for replacing the humidity of the soil.

The question of the functioning of the aquifers in the Kalahari formations remains to be addressed, if it is a matter of multi-layered or single-layered system and, in the case of multiple layers, how many layers it contains, which are the lithologies and the horizontal dimensions of each aquifer, if they are hydraulically interconnected, whereby these conditions present strong variations from one site to the next. The average productivity of the aquifers that have been installed in the deposits of the Kalahari vary between 1,5 and 18,5m3/h in these aquifers, with no correlation whatsoever between these rates and the depth of the aquifer levels.

In Angola, the aquifers that are known as Fractured Aquifers – that occur all over the Cunene River Basin wherever it is not occupied by porous aquifers nor by carbonated elements – are represented by two distinct groups of aquifers: those of the Gabbro-Anorthosite Complex and those of the Meta-sedimentary Formations.

In the system that is defined by the Gabbro-Anorthosite Complex the productive zones are situated in the regions with fractured or altered rocks, or in contact zones with other lithologies (ex.: veins, granite bodies, contact with the Kalahari formations, etc.), if these have not been filled by impermeable deposits. In the zone of Chiange, the most productive fractures are those in a N-S direction, the average producers are factures in E-W and NW-SE direction and those producing low volumes have a NE-SW direction; the flow volumes of between 3000 and 8500 l/s are generally orientated in fractures with a E-W and NW-SE direction; low flow volumes can usually be found in fractures with a NE-SW orientation or when the water points are situated in the zone at the source basin of mulolas. The average volumes for extraction for this type of aquifer can present the rate of 5m3/h. Much higher volumes were recorded in the Chitado region, sometimes higher than 30m3/h, even up to 70m3/h, generally in [bore]holes that are situated upstream from dolerite veins, close to mulolas that are intersected by these veins, whilst we have average values for the Chiange region of 8m3/h.

In the meta-sedimentary formations that are represented in Southern Angola by schists and other metamorphic rocks, and by tectonized and altered granites, the

Page 110/214 LNEC – Proc.605/1/11926 metamorphic rocks can provide extraction volumes of 0,6m3/h in fractured terrain; the altered granite presents potential flow volumes of between 3 and 30m3/h and can even attain 80m3/h.

The Predominantly Fractured Aquifers (Chela Formations) can be found in the siltite, clay and sandstone [formations] which present the characteristic behavior of a fractured aquifer. It has two main aquiferous levels – one up to 40m and another, deeper one that may extend to 150m – whereby the flow volumes may vary between 5m3/h (for the most superficial level) and 20m3/h (for the deepest level). The Chela Formations are sufficiently productive to supply the city of Lubango.

The Fractured Aquifers with Limited Potential (Granite or Granitoïd Rock) present a fissured character like all aquifers that are inserted in rock from the Pre-Cambric Era. Their productivity has only some value in the zones with intense fracturing and in those where altered rock is in contact with solid rock. The aquifers have a local distribution and its flow volumes vary between 1 to 5 l/s.

The most productive zones of this type of aquifer are: those where contact takes place with crystalline rock of different textures and composition, the areas with severely fractured granite-gneiss outcrops, the zones where contact takes place between igneous rock and schist formations, zones were faults and other fractures have not been filled in by impermeable deposits, [and] quartzite and basic veins and clefts.

5.2.2 Evaluation of underground water resources

For the assessment of existing underground water resources of a given region it is essential to know the water reserves of this region or, else, it is necessary to quantify the estimated volumes of water that flow into, and that discharge from, the region in question.

The underground water reserves can be broken down into two components: the constituent that refers to the soil (considering as such the zone up to the limit of the maximum depth of the roots of plants) and the component that refers to the region that is subjacent to the soil.

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What we are interested in knowing in view of the determination of underground water resources, i.e. the volumes of water that can be used without causing over- exploitation of the aquifers – when the consequences can [even] lead to a reduction in quality of the water, to an increase in cost of pumping and use of the resources, amongst other problems – is their water reserve.

In the process for adequate management of underground water resources, the most important factor to know is the effective recharge of the aquifers, then the water volumes that can be extracted without causing a drop in the piezometric levels, and consequently that the reduction in resources is equal to the volume of effective recharge, whereby the respective losses because of the supply of surface sources [wells] or percolation by lower-lying aquifers have to be deducted. Recharge represents the most important factor in the determination of economic potentials of aquifers, in particular in the regions with arid or semi-arid climatic conditions. It follows that in such climates the recharge [process] is rather heterogeneous, both in a spatial and in a temporal sense.

For the calculation of the recharge in the Cunene River Basin we opted for the use of the BALSEQ method (method of sequential daily water reserves), in view of the fact that the existing data for this basin would be the following: soil types and their geographic distribution, types of vegetation and their geographic distribution, daily flow volumes in the various water lines, average daily precipitation, average monthly evapotranspiration.

The BALSEQ model allows an evaluation of the monthly and annual average rates and the deviation patterns of the precipitation, potential evapotranspiration, actual evapotranspiration, surface drainage, surface infiltration, soil humidity and profound recharge of the aquifers, as well as the computation of the annual totals and averages of all the parameters, with the exception of the humidity of the soil.

It was necessary to divide the basin of the Cunene River into zones for the application of this model; this was done according to the types of soils and the vegetation that is currently in place. The soil types were obtained from the Soil Map of

Page 112/214 LNEC – Proc.605/1/11926 Angola and the vegetation coverage was based on the Phytogeographic Map of Angola and the data that were collected on the agricultural activity in this basin.

Once the results of the surface drainage and recharge were calculated by the model, the calibration of same was initiated. Thus the first scenario took a look at the recharge values that would correspond to a situation where the surface drainage that was calculated would correspond to the drainage that was measured in some hydrometric sections that are situated in the source area, equivalent to the areas that were affected by the seasons under consideration, or that would most closely resemble such source areas. Consistent with the results that were obtained with this calibration scenario, average recharge values were recorded for Huambo of 438mm/year, for Chianga of 385mm/year, for Sacaala of 371mm/year, for Lubango of 257mm/year, for Humpata of 241mm/year and for the Cunene station of the IIAA, OF 64mm/year. A regression calculated between the precipitation and recharge for these conditions indicates that the recharge zeroes out at values below 322mm/year.

A second scenario for calibration purposes took as a premise that the measured surface drainage would be less or equal to the sum total of the superficial drainage and recharge calculated by the BALSEQ model.

The results obtained from this scenario showed that, on average, for the region of Huambo the recharge would be to the tune of 249mm/year, 217mm/year for Chianga, 197mm/year for Sacaala, 175mm/year for the Lubango area, 166mm/year for Humpata, and 64mm/year for the IIAA station on the Cunene. The regression calculation of the average rates precipitation/recharge for the total of these stations – given a weighting to the rate for Huambo and Lubango in proportion of the number of years that were recorded (15 years) vs. the number of years of registration at the other stations (2 years), a practice that was also applied to the above-mentioned regressions - showed that, for precipitations below the isohyet of 95mm/year replenishing is literally inexistent.

Proceeding to the integration of the areas affected at each iso-line of recharge, the recharge for the various regions of the basin were obtained. It was confirmed by this method that the total seasonal replenishment in the basin would be contained between

Page 113/214 LNEC – Proc.605/1/11926 13.767hm3/year and 90.731hm3/year, of which the Namibian component would be between 88m3/year and 341hm3/year.

The average annual recharge (in mm) that would occur in the entire basin would be between 130mm/year and 190/mm year; with the average in the Angolan part being higher (between 120mm/year and 150mm/year) and that on the Namibian side an average of only between 6 and 24mm/year would be registered.

In the Sixties there were already problems reported as far as the drainage of the aquifers in Southern Angola were concerned and that were due to an over-exploitation of these resources. In the area of Caraculo this practice resulted in the drying-up of various [bore]holes whilst other water-points close to the source reduced by 1 to less than 0,2m3/h in the short period of 5 years. For the Fifties it was noted that the piezometric levels for 87% of the existing water-points in the Caraculo zone had decreased, an increasing tendency because of the expected increase in the number of extractions, whereby this reduction in level varied between 0,15 and 19,3m. As the climatic – and, in many areas lithologic – conditions of the extreme south of the basin of the Cunene River are similar to those in the Caraculo region, it can be assumed that similar problems may exist in that region.

Corresponding to the results that were obtained by the BALSEC model it was confirmed that, effectively, the recharge for the southern area of the basin is rather inadequate and of no significance in the case of precipitations below 200mm/year. Not only because of this aspect, but also because of the nature of the aquifers that exist in this region, a very careful use of the underground water resources of this entire area is recommended, in order to avoid any problems with the drainage of the aquifers and pronounced reduction in quality of these because of over-exploitation.

Page 114/214 LNEC – Proc.605/1/11926 6. PARTIAL EVALUATION OF WATER REQUIREMENTS

6.1 Introduction In the initial phase of the planning process it is necessary to identify the requirements and the prospects for the use of water as a matter of course. As the planning process progresses, the objectives need to be continuously reexamined in order to limit them to a specific number in order to develop alternative plans. Afterwards, when one put these water requirements side by side with availability, their utilization will have been determined to great detail as water is a limiting factor in semi-arid climates, like the one where most of the basin that is analyzed is situated.

The overall objectives of a plan for the supply of water resources, and more or less to a similar degree for the development of other natural resources like the soil and the biota, should include:  national economic development  protection of the environment  improvement of social well-being  preservation or improvement of the quality of water  public health and security  preservation of cultural resources  creation of leisure facilities [conditions]  preservation of scenery  guarantee of national security

The specific objectives for the Cunene River Basin, which is situated in a developing country, and, taking the geo-morphological characteristics of the basin into account, and those of the existing population, causes us to include the following in the evaluation of the water requirements for this basin:  water supply to rural areas  municipal water supply  supply for cattle watering purposes  water supply for irrigation purposes  water supply for industrial purposes  production of hydroelectric energy  protection against stormwater  assuring ecological flows  assuring flow volumes for Namibia.

The potential requirements were determined whilst taking amongst other elements the studies that had already been established for supply schemes on the

Page 115/214 LNEC – Proc.605/1/11926 Cunene River into account, as well as the information on current water use, and a preliminary forecast of the evolution of future requirements. We base ourselves on the premise of technical viability for each sector of utilization, independently from the other sectors. During subsequent phases, the incompatibility between the various utilizations will cause the elimination of some of them from the alternatives for the use of water resources.

6.2 Water supply to rural areas

The separation of the analysis of water requirements for the provision of water to the population, this crucial basic necessity, between the rural areas and the zones with pronounced urbanization, results from the differences in technical solutions for addressing them. The supply systems for the former are rather simple; they are independent, and relatively small. The latter require reticulation networks of some magnitude, may depend on various water sources, and require dependable solutions from a technical point of view.

The systems for supply water can be divided into three categories: the source of water, the treatment of water and its distribution. In the case of rural areas, it has to be acknowledged that it is only a matter of water sources and both the treatment and the distribution are largely absent, or are rather simplified and of small dimensions.

The typical rates of rural water consumption are of between 10 and 30 liters per day per person. In areas that are difficult to access, water consumption may be as little as 4 liters per day per person. The World Health Organization (WHO) has suggested that the supply of 20 liters per day per person would constitute the minimum, which might be difficult to achieve in some cases.

The water requirements for these rural systems have to take the people who need it into account, as well as the type of occupation of the terrain and the size of the population, and the technical means that are available in these areas. For the case of the Cunene River Basin, the determination of the population that should be reached by these simple systems is based on the data that was presented in Volume 6 of the 1st Report, “The Social Ecology of the Basin. Preliminary Recording”. In addition and in

Page 116/214 LNEC – Proc.605/1/11926 order to obtain a first ballpark figure, we used maps at a scale of 1/100.000 in order to verify the geographic distribution of the various populations. Even if the information provided by the map was outdated, it helped to consider the distribution of requirements for the basin, taking as a base the total numbers that were estimated for the year 1990 in each municipal area. We also used 7 sheets of the map at the scale of 1/100.000 of a more recent issue, from the Eighties, and some additional data that related to the years 1992 and 1993.

In 6 of the 22 municipal areas we applied a division of the population, whereby one section belonged to the basin and the other section was not part of it. This division was made for the purposes of weighting the area of a municipality in each of the two situations.

As far as the density of occupation is concerned, the total population figures fluctuate between 406 inhabitants/km2 in the Huambo municipality and rates of less than 1 inhabitant/km2 in the Tombua municipality. As expected, it is clear that there is a decrease in population density from north to south, from the area with most water to the most arid zone.

The method used to determine the density of human occupation in the rural environment hardly allows a scale of values, as they are indicated for each municipal area and expressed in a minimum and maximum. In order to obtain the minimum and maximum values two factors for the increase of the population were taken into account. It was confirmed that the range that was adopted was rather a large one, with a population that is estimated between 327.000 and 514.000 which means that there is a variation of around 60%. This variation could be considered to be compatible with the elaboration of the Plan for the Cunene River Basin. Firstly, as it is difficult to guarantee elements that are more reliable for this basin as far as a census of the population is concerned. Secondly, as the volume of rural water consumption would not be significant in comparison to other types of consumption, like for instance those for irrigation purposes. Once the populations of the various zones of the Cunene Basin were known, applying the actual capitations or those that were considered to be necessary, the volumes of water that is necessary for the supply of the rural population was computed.

Page 117/214 LNEC – Proc.605/1/11926 As already indicated above, the volumes per capita of 20 to 30 liters per day would be considered as an objective to be attained. In this case the minimum and maximum values for the supply of rural areas could be quantified. The daily water volumes were established in this manner, respectively by municipal area and by sub-basin. This allowed a comparison with the minimum available quantities, corresponding to the dry season.

In order to identify the requirements for the year 2020, it is necessary to establish a projection for the increase in water volume. However, this projection into the future is extremely difficult if we limit ourselves strictly to the rural environment.

As a matter of fact, the world-wide tendency is that the occupation of the soil in rural environments decreases, transferring the people towards the urban areas. Therefore, one of the means to resolve this question would be not to increase rural consumption, and rather concentrate all of the demographic growth on the increase of requirements for urban supply. Or even, as an alternative, to foresee a decrease in the water requirements for rural consumption, for the same reason.

However, an intermediate scenario was adopted, whereby the rural population would maintain a significant weight, with some increase of the capitations (intermediate values between rural and urban consumption). The average annual rate of increase of the population under these conditions was considered to be not more than 1%, less than the global rate of increase, which is 2,8%. The capitation was also slightly increased, with a volume of only 40 liters per person per day.

Based on the premises above, the total number of persons would increase by 35%. If one considers the increase in capitation of between a third and double, one reaches increases of water consumption by the rural populations of between 70% and 170% (see table 3). In this manner, the total forecast for human consumption in the rural areas of the Cunene River Basin has to be assessed at between 7hm3 and 10hm3. With an average volume of surface water that is available of 5800hm3, this amount represents only about 0,1 to 0,2%. It has to be noted that a large percentage of the water sources is subterraneous, which reduces the percentage that was mentioned above.

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Table 3 – Annual water volumes per basin that are required by the year 2020 for the rural areas of the Cunene (m3/day)

In terms of quantity, the average annual volume of water requirements for rural consumption is very easily secured.

Table 4 portrays the daily requirements. Comparing the daily requirements for the various sub-basins, which are comprised in volumes of between 18.000m3 and 28.000m3, with the corresponding minimum daily availability of around 2.600.000m3, it is obvious that the requirements make out only around 0,7 to 1,0% of what is available. Globally seen, the degree of latitude that is provided by the superficial system for the supply of rural areas is very substantial.

Page 119/214 LNEC – Proc.605/1/11926 Table 4 – Daily water volumes, per basin, for the human population in the rural areas of the Cunene m3/day)

The highest percentage of requirements as compared to availability can be encountered in the Alto Colui (Catembula) with 3,8%. The lowest rates can be found in the Central Cunene Region, with 0,02%. However, if the rural area is situated far from the Cunene River or its tributaries, it is more difficult or even impossible to ensure water supply for human consumption in the rural areas with surface water, with the natural flow volumes of the water-lines being smaller. Only recourse to underground water supplies can secure this, as practical experience has shown. This situation endorses the importance of the availability of underground water.

6.3 Water supply to urban areas

It is difficult to define typical rates for urban water consumption. As a matter of fact, these depend on the type of occupation of the urban area: exclusively residential, with industry, with public services, with irrigation of gardens, etc. In the residential areas, it also depends on personal consumption patterns, as well as on the standard of living of the population, which includes the degree of equipment with electric appliances.

Page 120/214 LNEC – Proc.605/1/11926 As a guideline for the Cunene Basin it is recognized that the per capita consumption would be of between 100 and 150 liters per day. Even more important is the assessment for the zones that are not exactly the urban nucleus. Another factor to take into account is the age and the extent of the network, as leakage has had a significant effect on total consumption.

The determination of the population in the urban areas was made in the same manner as for the rural areas.

The forecast is that the requirements for urban supply will increase. The rate of average annual population increase under these conditions was estimated at 4%, higher to that anticipated on a global basis with 2,8%. Per capita consumption was also increased, whereby now the relatively low rate of 200 liters per day was applied.

Keeping the problem of planning of water consumption in mind, Table 5 shows the rates that correspond to the year 2020, of the annual water volumes that are used for its consumption in the same zones, by sub-basin. Based on the above premise, the total population will have increased by around 235% by that year. If one takes this population increase into account, increases in consumption for the urban population increases by between 240% and 720%. In this manner, the total forecast for human consumption in the urban areas of the Cunene Basin has to be in the range of between 370hm3 and 470hm3. For an average volume of available surface water of 5700hm3, this amounts to a maximum of around 8%. It should be noted that, in many instances the water source is subterraneous, which reduces the above-mentioned percentage even more.

In Table 6 we present the daily water requirements. When comparing the water requirements overall with those corresponding to the minima that are available, it is confirmed that the requirements could correspond to around 40% or 50% of the available water. These rates show that the latitude provided by the surface system is small.

Page 121/214 LNEC – Proc.605/1/11926 Table 5 – Annual water volumes per basin, required by the year 2020 for the urban areas of the Cunene (hm3/year)

Table 6 – Daily water volumes per basin, for the human population in the urban areas of the Cunene (hm3/year)

Page 122/214 LNEC – Proc.605/1/11926 This situation emphasizes the importance of underground reserves.

The fact was verified that the most critical sub-basins are those of Caculavar (Cova do Leão) and Catapi, which show consumption rates that are higher by more than 200% as compared to the available superficial minima. In both cases it is impossible to ensure the supply for human consumption in the urban zones with the natural flow volumes for surface water, without [applying] pronounced regularization. It is only by introducing storage of surface water that the supply can be secured, if the underground water does not allow it.

If one analyzes the correlation between the annual requirements and annual availability, one can see that the most critical sub-basin is that of Catapi, in that the relationship between requirements and availability could be round 30%. As a consequence, adequate storage capacity could yet allow to satisfy the requirements for urban supply with the available surface water. As an alternative, there could be restrictions as far as the increase in population is concerned, seen that there is a lower rate of demographic growth in the areas where there are difficulties of supply.

In the Caculavar (Cova do Leão) the above-mentioned percentage would be 24%. In the Upper Cunene (Gove) the same percentage would amount to 14%, whilst that at Alto Calai could attain 12%. In all other basins the rates are lower than 3%.

6.4 Water supply for cattle

The determination of water requirements for the watering of cattle runs in parallel, to a certain degree, with the determination of water requirements for the supply of rural populations. It is difficult to point out a reliable average rate for the Cunene Basin, but based on scattered information, references to rates of between 2,4 and 23 heads of cattle per inhabitant could be found. For the purposes of assessing the requirements for the watering of cattle the ratio of 2 heads of cattle per inhabitant was taken as a basis. Cattle-breeding by traditional families takes place according to the principle of transhumance: during the rainy season the cattle is found far from the main bed of the Cunene River, due to the fact that there are large flooded areas; in the dry season the cattle will approach the river, taking advantage of the fresh pasture. The end

Page 123/214 LNEC – Proc.605/1/11926 of the dry season is the critical point, due to the substantial concentration of animals at the – every time fewer – watering points. In extreme cases there is no pasture where there is water, and where there is pasture there is no water, which obliges the cattle to cover long distances each day, sometimes up to 30km.

Intensive cattle-breeding does not correlate directly with the population, as it first and foremost depends on the presence of farms with pasture, in addition to easy access to water. To our knowledge there has never been a census on the number of heads of cattle held for intensive breeding purposes. There are some indications that the capacity of natural pasture would be of 4 to 6 heads of cattle per km2. During 1969, at least 3500km2 were forecast for intensive cattle-breeding. At that same time there was an indication of farms with an average surface of 100km2.

Typical rates for water consumption by cattle would be included in the range of 10 to 40 liters per day per head. Water consumption may decrease during crisis periods.

The method that was used for an estimate of the heads of cattle can only provide an indication of a range of rates, as there is a minimum and maximum limit set for each municipal area. The total that is obtained fluctuates between a lower threshold of 650.000 and an upper ceiling of 1.000.000, which seems compatible with the statistics for the entire country of Angola for 1992, of 3.200.000.

In excess of the amounts that were indicated per municipal area, the values per sub-basin were computed.

It is very difficult to correlate the average annual increase in heads of cattle with the population growth under these conditions (it was deemed to be only 1%). On the other hand, it is not at all possible to forecast the transition from traditional cattle- breeding to semi-intensive cattle-farming in the rural areas. In the latter case, the capitation needs to be increased, and one could assume a rate of 20 liters per day per head of cattle.

Page 124/214 LNEC – Proc.605/1/11926 Table 7 – Annual water volumes, per basin, required by the year 2020 for livestock in the rural areas (hm3/year)

Table 8 – Daily water volume, per basin, for livestock in the rural areas by the year 2020 (m3/day)

Page 125/214 LNEC – Proc.605/1/11926 Keeping just the problem for the planning of water utilization in mind, Table 7 shows the volumes that correspond to the year 2020, of the annual water volumes used by consume in the same zones, detailed by sub-basin.

The total number of heads of cattle, based on the previously expressed, will have increased by around 35%.

If one takes an increase in capitation by the double into account, one arrives at an increase in water consumption for cattle of 170%. Table 8 shows the daily requirements for cattle-watering.

In conclusion, a parallelism exists between the future projections for the population in rural areas and for the watering of cattle, in as far as the necessary water quantities are concerned. It is evident that some assumptions might be debatable. Our reasoning is based on the premise that pastoral cultures would be upheld by a part of the rural population. Any change in this reasoning would imply that there would be a different correlation between the population and the number of heads of cattle, which would imply deviations resulting in an increase or a decrease of water consumption.

Finally, it is necessary to mention that, as far as cattle is concerned, both the availability of water and pasture are essential, or otherwise [the provision of] alternative fodder. As regards this aspect it will also be necessary to cross-reference information on the availability of land for pasture and the requirements regarding land for agriculture. Joint management of these two types of land-use is a prime aspect in the question on cattle.

6.5 Water supply for irrigation purposes

Planning of agricultural schemes require a vast basis from a hydrologic point of view, in order to determine the water that is available, and from an engineering standpoint, in order to ensure a reliable hydraulic structure and exploration. The other indispensable components are the assessment of the soils that are likely to be irrigated, the definition of land use from an organizational point of view (more or less business-

Page 126/214 LNEC – Proc.605/1/11926 related), the economics of agriculture in which one might include the choice of crops, and not forgetting the environmental aspects.

Altogether, the planning of irrigation has to include five essential aspects, being technical, financial, social, economical and environmental.

On the Cunene, it will probably be a matter to find a middle ground between the most sophisticated and automated systems (used on industrial farms) and more unsophisticated systems (used in areas with traditional agricultural occupation). Both extremes may need to co-exist.

The irrigation of areas with traditional agricultural occupation may ensure a more efficient production by the existing entities, as it would not imply any displacement by the population, therefore associating the increment in agricultural production with social stability. However, there is one uncertain factor as far as the economic advantages are concerned as, on the one hand, the major costs regarding infrastructures for the transport of water (just one of the many cost factors) may bring about abstention from the use of complex external management systems and some supporting services.

In the Cunene Basin the land that can be irrigated is limited to certain areas in the central Basin, and in particular to the triangle between Mulondo, Cahama and Calueque.

Figure 30, with the zoning of the types of irrigation, clearly explains the correlation between the proposals for the various degrees of irrigation and the latitude. The variation in water requirement by latitude is naturally associated with the decrease in water towards the south and, as a consequence, to an increased need to store water from the wet season for the dry season.

In this manner, in the north of the basin, the irrigation is only a compensation for a naturally viable crop production in [periods of] drought. The volumes that are required are relatively minor, as there is more water all along the year, [which would result in] a small scheme that is easy to implement. As water security is more easily attainable, at the level of the Master Plan, at first hand it will not be necessary to macroscopically

Page 127/214 LNEC – Proc.605/1/11926 define the number and detail the position of the supply points. Otherwise said, whichever are the local solutions, they will not influence the overall hydrological conditions downstream to any significant extent.

On the other hand, in the drier zone, where the volume of water that is required for irrigation is relatively more important, it will be ever more necessary to define large schemes, as major volumes are required for [proper] management of the dams, and as the rivers are either seasonal or even sporadic.

The following cartographic areas can be identified from north to south:

1) Irrigated nucleus of Matala-Capelongo. The only area outside of the Lower Cunene and which includes the former irrigation perimeter, [which was] supplied by the Matala scheme. Various distribution points on the left bank of the Cunene and the Calonga Valley are encircled. This area includes two cartographic zones

(A1 and A2) with a total of 3780ha. 2) Inter-fluvial between the Cunene and Colui Rivers, or Calonga, with its fold-line that by and large follows a N-S axis, which divides the two basins into relatively equal parts, defining the surfaces and lateral discharges for both sides, and countering in this manner the inconveniences that relate to the retention of excess water. It sets out with a width of 25km at the northern edge, funneling

towards the confluence of the two rivers close to the settlement of Quiteve (A3). It has a surface of around 69.000ha. 3) A narrow ledge on the lower Cunene, on the left bank and from which it is separated by a shoulder with only a few meters of gradient. A strip with a width of between 1 and 3km, with a length of around 160km or otherwise said, from the

confluence of the Calonga up to Naulila (A3 + A2). It covers a total area of 39.000ha. 4) The Mulondo Zone, on the elevated platform on the right bank of the Cunene, is

not affected by drainage problems (A3); it has a width of around 50km and a surface of 8.200ha. 5) The array of sections with limited surfaces that separate the alluvial basins of the

Caculuvar and Calovango Rivers (A2), with an area of 4.400ha.

Page 128/214 LNEC – Proc.605/1/11926

LEGEND: Limite da Bacia Hidrográfica = Boundary of Hydrographic Basin Limite da Sub-bacia = Boundary of Sub-basin Curso de água = Water course Capital deProvíncia = Provincial capital Estação hidrométrica = Hydrometric station Fornteira = Border Terras a irrigar = Land that is to be irrigated Área Cartográfica = Cartographic area

Figure 30 – Areas for irrigation in the Cunene Basin

Page 129/214 LNEC – Proc.605/1/11926

6) The coastal surface that is very smooth and that extends from the Calovango valley to the area around Tchipa, skirting the valleys of the Caculuvar and the

Cunene (A3 + A2) over a distance of 15 to 25km. The lower edge is delimitated by the grade that transits towards the higher sandy level (“tunda”). It has a total surface of around 59.000ha. 7) A series of sections in the Humbe-Katequero Zone, with a privileged situation in as far as ways of communication and accessibility of water for irrigation purposes from the Cunene is concerned. The area in question comprises around 13.000ha. 8) A zone at the edge of the surface of the Lower Cunene, with a N-S extension of around 30km, and a width of around 2/3km, with excellent localization as regards

the river that is easily accessible for the extraction of water for irrigation (A2). It has a surface of around 8.000ha. 9) A section of the flat surface that inserts itself between the edge of the “tunda” to the west, and the clay areas that border the Lower Cunene to the east, with a N- S extension of around 30km, mainly between Donguena and Calueque, and an

average width of 2/3km (A2). This area includes around 8.000ha.

All the areas that have been examined as regards irrigation, pertaining to category A, make up a total of almost 212.000ha. The actual occupation of this land includes the “lavras” [small traditional agricultural units] with millet and massambala crops, subsistence agriculture, areas for pasturage on untilled or fallow land in the valleys of the Calonga, untilled land that has been made available for grazing. There are also areas that are already involved in irrigation, like for instance those of Matala- Capelongo, where potatoes, tomatoes and horticultural products are farmed in addition to millet and beans.

In some zones, mainly in the extended section 3), there is an incidence of settlement by the population, which is strategically situated between the grazing zone of the interior and the access to watering of the cattle on the Cunene. There are also average-sized exploitations between Cafu and Xangongo, with orchards, horticulture and millet.

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In the extended section 6) no fixed populations were recorded, as these are the areas where cattle can graze the entire year. Conversely, in sections 7) and 8) the rural occupation is rather concentrated, a fact that stems from the good living conditions during the year, where the soil is permanently drained which allows easy cultivation of the soil, but still maintaining access to water for grazing purposes.

The brief description on the current situation as far as human occupation is concerned already indicates the coexistence, in the area that under examination for irrigation, of two situations. For one of the situations it will be easy to implement large- scale irrigation schemes in areas where no major occupation exists at present. On the other hand, the other one should allow for a tendency to implement scattered irrigation for the current “lavras”, that are settled in irrigation schemes that have to be adapted for the existing of population.

In parallel, and independently from the two possible scenarios [above], the irrigation schemes could resort to large and medium regularization dams or extract directly from the rivers, from the Cunene or other waterways, as soon as [proper] regularization has been introduced upstream from such extraction points. The choice between the two hypotheses depends on the distance between the land that is to be irrigated and the sources of the water that is are to be utilized.

Only the land pertaining to category A was taken into consideration, which means a total of 211.290ha. The main crops to be produced by means of irrigation were analyzed, whereby [the merits of] cotton, almonds, rice, sugar cane, citrus, sunflower, lucerne, massambala, millet, horticultural products, potato, onion, tomato, soy beans, tobacco and wheat were assessed. Other crops may be considered at a later stage, in particular sweet potato, massango, macunde beans, elephant grass, and fruit like mango, guava, passion fruit and avocado pear.

The forecasts for water consumption for irrigation purposes, in agreement with the requirements and the characteristics of the pedologic-climatic environment, are made on the basis of the scarce data that correspond to the behavior of these crops

Page 131/214 LNEC – Proc.605/1/11926 under irrigation conditions. The most precarious elements are the ones on the subject of evaporation and evapotranspiration.

During the planting-periods of the annual cycle, that occur between the months of May and September, and between November and April, depending on the crops, the number of irrigation [episodes] per year would be of between 12 and 26, which would lead to estimates with a rate of 300mm/ha for almonds and for tobacco, during the rainy season, to a maximum of 960mm/ha for rice. The average of the values is 470mm/ha.

For perennial crops, with a number of irrigation cycles of between 40 and 45, consumption [rates] of between 1050mm/ha for sugar cane and lucerne, and 1225mm/ha for citrus were forecast.

For the purposes of overall quantification of irrigation requirements, in this phase of the elaboration of the Master Plan it is only of interest to provide the notion of the key figures. For this reason, using only the minima and maxima consumption rates, Table 9 was developed and which quantifies the requirements for irrigation in two ways: by annual water volumes, per basin, and with the flow volumes.

Table 9 – Annual water volumes (hm3/year) and flow volumes (m3/s), per basin, required for irrigation purposes in the Cunene River Basin

Taking the distribution of water points for irrigation into consideration, the consumption rates that are presented in Table 9, the volumes of available water from the above-mentioned basins, and also taking the existence of provision from regulated flow volumes into account, it can be verified that, on average, the irrigation of the entire land [under consideration] would require around 47% of the total available water. This

Page 132/214 LNEC – Proc.605/1/11926 percentage could rise up to 70% for critical periods. As a result, one can also confirm that restrictions are to be expected for the utilization of all the land that has been examined the purposes of future irrigation.

The land that is situated in the sub-basin of Xangongo could require, on average, around 27% of the available water, [a percentage] that could increase to 41% in critical periods. On the other hand, the land that is situated in the sub-basin of Ruacana could require on average around 15% of the available water, which would increase to 23% in critical periods. The remaining land would require respective percentages of between 5% and 7% for the same kinds of situation.

A similar analysis compared the requirements in daily rates with the minimum availability figures and came to the conclusion that it is only in the Folgares Basin that irrigation can be introduced without regulatory intervention. As a matter of fact, the necessary percentage of flow volume for this basin, when comparing the minimum rates, would be of around 24%. In the other areas the requirements are more important, with percentages of between 142 and 775%. As a consequence, irrigation will only be possible all over the areas that have been identified, after the intervention of hydraulic works that regulate the flow volumes of the river.

6.6 [missing in both index and text]

6.7 Water consumption and water restrictions

Water supply for the people, whether in rural or urban areas, for the cattle which is of fundamental importance for the rural population, and for irrigation, constitutes the conjunction of large water users. The ones have precedence as they are essential for the existence of the population, others are very important because of their bulk. The sum total of these requirements provide a first indication as far as the zones of the basin with the greatest need for water are concerned, whereby one may previously identify the zones that have a potential lack of water, where a certain degree of water restrictions should be introduced, where greater flexibility exists or where no problem is foreseeable.

This analysis will be presented for the target year 2020, whereby it is assumed that full development of irrigation has taken place by that date.

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Taking the annual water volumes per basin into consideration that are necessary for the various uses, as well as the respective daily volumes, Tables 10 and 11 were obtained.

From Table 10, and from the similarity that exists with the consumption rates for each sector, the requirements can be analyzed in view of the structure [hierarchy by volume] of availability. In this manner, the total that is foreseen for bulk users in the Cunene Basin will be contained between 1.000hm3 and 3.000hm3. For an average available volume of surface water of 57.000hm3 this rate represents between 18 and 54%.

In the basins of the Catapi, the Central Cunene (Xangongo) and Caculuvar (Cova do Leão), this percentage may present maxima of respectively 31, 29 and 25%. In the basins of Central Cunene (Ruacana), Upper Cunene (Gove) and Alto Calai the same percentage may be of 16, 14 and 12% respectively, whilst the values in the remaining basins will be less than 5%.

Table 10 – Annual water volumes, per basin, required by the year 2020 for bulk consumers (hm3/year)

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Table 11 portrays the daily requirements. Comparing the daily requirements to the total for the various sub-basins, comprised between 13,2x106m3 and 26,6x106m3, with the corresponding daily minimum availabilities of around 19,8x106m3, it is clear that all the requirements cannot be satisfied without some serious seasonal regularization. The importance of underground reserves becomes apparent in this situation.

It is evident that the sub-basins that are the most problematical are those of Xangongo, Ruacana and Catapi, which show consumption rates that are higher by more than 200% as compared to the minimum available surface water, and that they can attain up to 800%. In both cases it is impossible to assure full forecasted supply by means of natural flow volumes. In some cases not even recourse to storage of surface water can assure full supply in case of insufficient underground water.

The figures that are presented indicate clearly that the premises on consumption on which this first analysis of the utilization of water in the Cunene River Basin is based are optimistic. As a matter of fact, in the stimulation phase the water utilization rates in some zones of the basin will have to be reduced in order to render them adequate to the available water once that has been regularized.

Table 11 – Daily water volumes, per basin, required by the year 2020 for bulk consumers (x106 m3/day)

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The quantification of the other consumption categories was not made to the same detail as that for bulk consumers. One of the reasons is the major difficulty in forecasting consumption without having defined any scenarios for socio-economic development. Another reason is the relatively smaller importance to ultimate consumption. This is related to the hierarchy of consumption categories. The order for presenting consumption categories corresponded to a classification that was assumed by the authors of the study. This might be changed if other premises are substituted.

Beyond the consumption categories one needs to address the restrictions [to be applied] to the use of water. As a matter of fact, the analysis has hardly taken the potential consumers into account in as far as quantities were concerned. However, each consumption depends, on the one hand, on the quality of the water that is available, and, on the other hand, on the degree [cascade] of utilizations, with those with and without consumption situated upstream, and sometimes, also downstream. It is only in the simulation phase that these interdependencies will be examined.

The requirements for industrial purposes can be divided into two major categories. One of these categories was already examined, and corresponds to the industries that are situated in urban zones, and which are usually computed as part of the urban capitations. The other category embraces the industries that are scattered all over the basin. The small, isolated industry does not require great preoccupation within the framework of this plan, as it can be supplied within the scope of surplus water resources. One might say that, once the basins are identified that provide surplus water, [potential] business activity might be channeled towards these zones.

The industry that is associated to agricultural activity is largely dependent on the choice of crops, and, because of the range of volumes that are utilized by the estimate for irrigation purposes, they have been included in this phase of the Plan.

The mining industry is developed in accordance with the existence of deposits. The water requirements for this activity depend largely on the degree of processing that is done to the minerals. In the Cunene Basin, in Angola, the zones with major potential for mining activities are situated in the area close to the source of the river, in particular

Page 136/214 LNEC – Proc.605/1/11926 in the vicinity of the line Lubango-Chibia (a sub-basin of the Caculuvar), in the Upper Cunene, between Huambo and the confluence of the Cuando with the Cunene, in the axis Kuvango-Cassinga, i.e. in the sub-basin of Colui, and finally, in the sub-basins on the right bank of the Cunene River, between Chitado and the river‟s mouth. In some of these zones there may be some competition regarding the use of water. If this is the case, it will be necessary to carefully look at the availability of water for mining activities.

In relative terms, it is the first zone, namely the sub-basin of the Caculuvar, where the pressure regarding the need of water is most intense. A quarter of the average annual water volume must be made available for preferential consumption. In a drought period the water requirement is forecasted to be more than double the [available] surface water.

There may be competition for water use on the Upper Cunene, depending on the locality. In the northern areas there is more need of water, and the requirement may correspond to around 15% of the annually available volume, decreasing towards the south towards a negligible percentage. In the dry period the percentage may soar to 60% of the maximum, but a large degree of freedom of use of the water will continue to exist in other localities.

In the two remaining zones there is quasi no competition as far as the use of water is concerned, in the Colui and downstream from Ruacana; but in this latter case it is very scarce.

By decreasing order of importance the consumed volumes are indicated for the various categories of use. The additional values indicate the restoration flows: Irrigation – consumption 80% and restoration 20% of the flow volume; Industry – consumption 30% and restoration 70% of the flow volume; Supply – consumption 20% and restoration 80%; Refrigeration – consumption 1% and restoration 99% of flow volume.

A more detailed analysis will show that the large water consumer, namely agricultural activity, can show a vast variation in consumption, depending on the irrigation method that is employed. The consumption may decrease to 30%. The

Page 137/214 LNEC – Proc.605/1/11926 pollution that is produced depends on the fertilization methods and is very difficult to control as it is scattered.

Pollution in urban areas may contain a large proportion of organic material, but also other types of waste may emerge because of the presence of a large variety of industrial activities. Industrial pollution depends strongly on the type of industry. In both cases a large majority of the disposal is consistent, which allows easier control.

The use in refrigeration, with a very low consumption, can result in some cases in thermic pollution that is reasonably localized, but not always negligible because of the strong impact it may have on the biota.

The Cunene Basin has an appreciable potential for the production of hydroelectric energy, and for many years studies have been carried out on this subject. First the Matala Dam, then that of Ruacana, have been the main production centers. The Gove Dam was also envisaged as a production center, in addition to its function of regulating the flow volumes for the two schemes that are situated downstream.

The production of electricity does not consume water (if one does not take the increase in evaporation into account that takes place in the dams) but can have significant implications for other utilizations. These may [for instance] be important in the availability of water pressure, when there are significant fluctuations in daily flow volumes, and tend to be of lesser importance in schemes with continuous production.

As far as identification of water requirements are concerned, electricity production does not play a role as no consumption takes place, but it is important to identify the sites along the river that are the most appropriate [for this purpose]. For this identification the definition of pressure, that is a linear function of two variables: the flow volume, identification of the availability of water and, the fall height of the station which depends on the geomorphology of the basin. This identification is not made in the present Report.

It makes more sense to forecast the electricity requirements for the basin and to compare them to the production potential thereof by hydraulic means, than to predict the

Page 138/214 LNEC – Proc.605/1/11926 “requirements” of water for electricity production. If the power requirements would be less than the capacity for hydro-electric production, the basin would be self-sufficient, with the production system containing installations for electricity production and with adequate pressure to reach the points of consumption. If requirements would be higher, reversible turbine-pump installations could be envisaged in order to optimize the overall functioning of the electrical grid.

According to recent information, the electricity production in Angola in 1990 was of around 935 x 106 kWh for a total of 11x106 inhabitants, which amounts to a capitation of 85 kWh/inhabitant. In order for this capitation to reasonably meet the actual requirements in the Cunene Basin it should be around 170 x106 kWh.

With the socio-economic development the electricity requirement could be increased to rates of around 500 kWh/inhabitant. If one multiplies this capitation by 7 x106 inhabitants, a total future requirement of around 3500 x106 kWh, i.e., 3500 GWh would be predicted.

Previous schemes for water supply estimated assured electricity production at 1.000 GWh, and the producible at 9.000 GWh. These numbers prove that, with a moderate development scenario the basin can produce sufficient electricity for its requirements, but in the case of a more optimistic scenario the total capacity would be insufficient.

6.8 The flow of water to Namibia

When the entities that share water are two independent countries, the elaboration of the Master Plans becomes much more complex and requires lengthy negotiations.

In an international basin, the elaboration of a Master Plan may be carried out by depreciating the existence of the borders, embracing all requirements regarding the use of water in a single series, independently of its nationality. However, this is not the most employed method because of different territorial sovereignties. On the other hand, each

Page 139/214 LNEC – Proc.605/1/11926 country usually identifies its requirements separately, and subsequently the negotiations regarding allocation/sharing take place by means of bilateral commissions.

There have been negotiations over many years on the sharing of water from the Cunene Basin, as a valid Accord applies, and negotiations are underway for the elaboration of a new agreement. For this reason the elaboration of a Master Plan – where the present report is meant to be included – is extremely important.

According to the currently binding Accord, that was adopted by the two countries of Angola and Namibia after they became independent, no more than 50% of the regulated discharge of the Cunene River was to be extracted for non-conservative purposes, i.e. for irrigation, which would correspond to a flow volume of 40m3/s. The comparison of this flow volume with the rates that would be required for irrigation, presented in Table 9, leads to the conclusion that, according to the Accord, irrigation would be limited to a percentage of between 30 and 70% of the maximum that would benefit the land that showed potential, consistent with the scenarios for supply.

On the other hand, in view of the fact that the supply for human consumption has priority over any other use, even if it may not be conservative in nature, it had to be foreseen that the economic development in the Cunene Basin will reduce the flows to Namibia in the medium term. Such a reduction should not be interpreted as an action that contravenes the Accord. The flow volumes in question could be to the tune of 15m3/s.

At present there are negotiations in progress on the establishment of a new Accord between Angola and Namibia for the Supply of Water Resources from the Cunene River Basin. In view of what was mentioned above, it seems obvious that the allotment of water of this river is subject to some difficulties as it has the tendency to be [too] scarce as compared to all forecasted potentialities, which is normal for the climatic characteristics of the basin, in which there are semi-arid to desert regions.

A more simplistic alternative would be to adjust the existing Accord by means of an update of the premises that it was based on. Another alternative is to start out with a total freedom of choice, based on other premises, even if these are completely different

Page 140/214 LNEC – Proc.605/1/11926 from the previous ones. For a question of methodology for the Master Plan, providing freedom as regards the politico-technical conversations, the rules of the Helsinki Accord could be brought into play.

According to these Rules, each State of a hydrographic basin has the right, within the boundaries of its territory, to reasonably and equitably benefit from the utilization of a part of the water resources of the international basin (Article IV).

Reasonable and equitable shares can be determined on the basis of important factors that have to be taken into account for each particular case (Article V, Nr.1).

In Nr.2 of the same Article V 11 important factors are mentioned. In Nr.3 we find confirmation that the weighting that is to be applied to each factor has to be determined on the basis of its importance in relation to the other significant factors. Thus the combination of factors and weighting can be verified that lead to a high number of alternatives for equitable sharing. This is by itself a reason for the usually extended period that is necessary for negotiations on [the subject of] sharing of water between two States.

The 1st important factor is the one regarding the hydrographic basin, including in particular the extension of the drainage area that is part of each State. In the present case, where the [drainage] area in Angola amounts to over 87%, direct application of this factor would give Namibia a value to the tune of 740hm3/year, an average flow volume of 24m3/s and a maximum deviation of flow volume without regulation of 4m3/s.

The 2nd factor is the hydrology of the hydrographic basin, including in particular the contribution by each State towards the drainage of the basin. Direct application of this would again be to the greater benefit of Angola. As the territory in Namibia is situated in a quasi desert zone, the hydrologic contribution of this country is negligible when it is compared to the Angolan contribution. In complying with this factor Namibia would have access to an insignificant percentage of the water.

Page 141/214 LNEC – Proc.605/1/11926 The 3rd factor resembles to the previous one, these are the climatic elements that affect the hydrographic basin. Distribution of precipitation, of evapotranspiration, of surface drainage, of humidity in the air are also part of factor Nr.2.

The 4th factor relates to the utilization of water resources as they were established in the past and [are now] in the present for each of the States of the hydrographic basin. An analysis of sharing, based on the Accord, was already referred to.

The 5th factor looks at the economic and social requirements of each State in the hydrographic basin. This factor may give rise to two interpretations. On the one hand, it would be to give preference to the most needy from an economic point of view, which may not correspond to the one who needs the most water. Thus it is necessary in the course of the negotiation process, in addition to the types of utilization of water alone, to look at the economic aspects in conjunction with the sharing of the volume of water.

The 6th factor is the one of the population that depends on the water resources of the hydrographic basin, in each State. The far larger population in Angola in the Cunene Basin would result in an insignificant percentage of the available water for Namibia.

The 7th factor relates to the comparison of costs of the various alternatives that could ensure the satisfaction of economic and social needs of each State. This factor is related to the 5th factor, and the same observations apply.

The 8th factor looks at the existence of other water resources that are available, over and above the international hydrographic basin. As a matter of fact, the signed Accord already took this into account as part of the water that is collected at Calueque is transferred via a basin in the vicinity. On the other hand, Angola has other basins it can make use of in the region, with water reserves that could contribute water to the area of the Cunene River Basin, in particular in the source areas where the two large urban agglomerations are concentrated.

Page 142/214 LNEC – Proc.605/1/11926 The 9th factor concerns the utilization of water resources by avoiding unnecessary water loss. It has to do with adequate water management in each of the two States.

The 10th factor is the viability of compensation between one or more States of the hydrographic basin as a means of conciliating the various utilizations of water that could cause conflict.

Finally, the 11th factor corresponds to the degree in which the requirements of a State involved in a hydrographic basin could be satisfied without affecting to a substantial degree other states on the same hydrographic basin.

Another Article that is important is VII, relating that a State on a hydrographic basin cannot deny actual and reasonable utilization of water resources, with the view to secure future use of these same resources for another State of the same hydrographic basin.

Based on these Rules, allocation of water in the Cunene River Basin may vary between the use by equal shares, which would correspond more or less to the present Accord, and the predominance of one of the States, which would be the one with the largest geographical share, being Angola.

7. SIMULATION OF THE SUPPLY OF WATER RESOURCES

7.1 Introduction

The main objective of the [Master] Plan for the Integrated Utilization of the Water Resources of the Hydrographic Basin of the Cunene River is to resolve the problems, the requirements, and the opportunities for use that are inherent to the presence of water.

In the first phase of the planning process the identification of the problems, the requirements and the opportunities for use of water is therefore of a general nature. As the planning proceeds, the objectives need to be continuously reexamined in order to

Page 143/214 LNEC – Proc.605/1/11926 limit them to a specific number that allow the development of alternative plans. The supply of the water resources was based on the knowledge of the available resources and the requirements for the use of water in the Cunene River Basin. Based on this information, scenarios for the utilization of water can be constructed, which presupposes the adoption of various scenarios on the development of the various economic sectors.

The economic evolution of a region of a country has an impact on the utilization of water. It is normal [logical] that major hydraulic schemes for the supply of water are necessary to go together with the economic and social development. Therefore continuous planning on these hydraulic schemes needs to take place and their respective implementation. The planning process requires the input of a vast amount of data.

At present the analysis of systems and the increasing availability of computers provide the necessary tools for the required analyses for an evaluation of various plausible solutions for the planning of water utilization. Not only do the computers accelerate the analysis of the problems, they also allow automatic access to data bases and analyses by computer has become essential in order to cope with the vast volumes of data that this analysis calls for.

At the forefront of the analysis for the utilization of water there must be other sectorial plans in existence on the economy of the region and the country. These sectorial plans may play a controlling role as regards the utilization of water. But on the other hand, they may also prepare the ground for the other plans, as in some cases the order of precedence may be reversed, i.e., that the plan for the utilization of water prepares the ground for another plan, or other plans, for the sector. In both cases the plans may correspond to different subdivisions of the territory, as a hydrographic basin could for instance be considered as a unit. . The difficulty with planning stems from these different approaches, if one takes one sector as a priority or else, another. Over and above these different priorities, the objective of each sector is to optimize its economic advantages, which may come into conflict with the optimization for another sector.

Page 144/214 LNEC – Proc.605/1/11926 In order to resolve these conflicts it is necessary to define the various alternative scenarios, so that one can favor the various sectors involved to different degrees, and to proceed to simulations that allow the assessment of the consequences. The choice of the criteria for analysis is ever more important for the final result of the simulation. As a result, the analysis of the merits and drawbacks of the alternatives is always to some degree conditioned by that choice, leading normally to final solutions that are based on political decisions.

The definition of scenarios for the development is made with different priorities for the use of water, based on the following order of priorities: - the supply of water to the population - the supply of water for cattle-farming - the supply of water for irrigation purposes - the production of hydroelectric energy - the conservation, preservation and improvement of aquatic life - the supply to water for industrial purposes.

The two initial priorities imply: - an increase in minimum flow volumes - an improvement in water quality - a guarantee of ecological flow volumes

In addition, and taking the occurrence of high flow volume rates into account, the plan has to bear in mind - soil conservation, in order to prevent loss of a resource that is difficult to renew; - reduction of damage caused by rainfall; - fluvial correction and stormwater control.

Finally, and in a parallel plan, the guarantee of flow volumes for Namibia will be analyzed.

7.2 The IRAS simulation model

7.2.1 Introduction

The IRAS simulation model is a computer program. IRAS stands for Interactive River-Aquifer simulation. This program allows the simulation of a variation in time of river flows, of the volumes of stored water, of the quantity of water, the electricity produced

Page 145/214 LNEC – Proc.605/1/11926 and the consumption of water collected from surface water or from aquifers, or from a system that combines both surface water and aquifers.

IRAS was developed for the evaluation of efficiency and impacts of various alternative schemes and for different policies of operation of the systems of water resources. The systems may include different rivers that are interlinked and also multiple aquifers that serve extended areas. But it can also be used for a section of a river and for a small hydrographic basin. The user of IRAS can define and has control over the spatial and temporal resolution of the system that is being simulated.

The systems that can be simulated by means of IRAS can be represented by a grid of nodal points and arcs. The user has to design the grid that can contain up to 60 nodal points and 60 arcs.

The nodal points in the grid represent dams, lakes, sites where water is consumed, hydrometric stations, aquifers, confluences and catchments. One nodal point can [in fact] be a combination of various types of nodal points.

The arcs in the grid can be either unidirectional (discharge in one single direction) or bidirectional (discharge in two directions, like for example in the case of pump-turbines, or for the discharges that depend on variations in levels). The arcs represent river sections and transference of water between aquifers and/or wet zones and the surface system.

IRAS has the capacity to simulate systems of water resources for parts of a year, or for periods that encompass several years. Each period that is shorter than a year is divided into various episodes for calculation. The user has to define the number (up to 60) and the duration (a day or more) of the simulation episode. One simulation may include any number of years, parts of years, and discharge sequences.

The applications of IRAS can just involve the forecast, in space and in time, of values, or of defined functions of values, of the simulated variables for a variety of inputs on hydrological or water-quality parameters. The results for a particular nodal point or arc can be presented in a temporal series. Color coding (green, yellow and red) can be

Page 146/214 LNEC – Proc.605/1/11926 assigned to the various ranges of values, at the user‟s discretion, to represent the various degrees of satisfaction, to quickly identify the [various] zones of the system according to space and time, and which could represent problem areas.

The applications could also include the forecast of statistics and probabilities of distribution of possible duration and extent of deficits, considering stored volumes, the production of hydroelectric energy, or the appropriateness of concentrating on the quality of the water, and this in various locales within the system. The results of multiple simulations can be compared.

7.2.2 The simulation process

The simulation process by means of IRAS intends to reproduce the replication of the utilization of the water resources. Each phase of the simulation influences its aptness and representativeness of the results and the necessary number of reiterations throughout the simulation process.

In the first block of the simulation the objectives of the study are identified, and the capacity and the limitations of IRAS are assessed. This program can be used to assess the effectiveness of any configuration of the system and any cluster of operations, but cannot automatically identify the alternatives for the project or operational policies [to be adopted/applied]. IRAS does not contain a system for optimization that is capable of eliminating the specification of operating policies and it is [therefore] always necessary to choose solutions.

The second block of the simulation contains the compilation of data for the definition of the system and its operation, including hydrological data, the requirements, consumption [figures], pollution factors, etc. Files are prepared with the input data for the simulation. Simulations by IRAS depend mainly on the collection of data on flow volumes at hydrometric stations, that one might label “uncontrolled” data. These are the basis for simulations and can be interpolated from a spatial point of view with other sites by means of “station multipliers”. The gathering of these discharge data, of losses occurred through evaporation or infiltration, and of the replenishment of aquifers, is the part that is

Page 147/214 LNEC – Proc.605/1/11926 most labor-intensive for the application of IRAS on any given system. The errors in such input data will affect the rigor of simulation and its results to a significant degree.

In the third block the grid of the system and its components are defined schematically, as well as the capacities for storage of water and the rules for operation. In the fourth block the simulations are carried out and the results are examined and evaluated. The IRAS program was developed mainly to increase efficiency of the elaboration of these two blocks. If the tasks included in the first two blocks were carried out properly IRAS is able to reduce the efforts that are linked to the planning of studies of water resources of a hydrographic basin.

The presentation of the results and the statistical analyses that are incorporated into IRAS help the users to identify and to understand the simulations. The presentation techniques for visualization on PC screens include diagrams with temporal and spatial series of the variables and the functions of these variables that were selected by the user, as well as color graphs on digitalized maps, both static and dynamic, of the efficiency of the alternatives of the measurements that were implemented by the system. The statistical presentations include reliability, resilience and vulnerabilities of the system as well as unconditional and conditional probability projections of the same measurements as per the sites that were selected by the user.

The IRAS simulation program has been used to examine problems regarding water management, including the forecast of impacts of extensive pollution on a daily basis, for a small basin. The same program has been applied to study the problems of water supply and of hydroelectric energy and other uses in vast regions. However, it has to be made clear that, whilst the simulation program allows considerable latitude in as far as spatial and temporal resolutions of the system of water resources under investigation are concerned, the simplified methods and the requirements for data of this program make it more appropriate for extensive hydrologic simulations for regional systems, like the Cunene River Basin, rather than carrying out detailed hydraulic simulations for local systems.

The applications of IRAS can include forecasting for probability projections of possible discharge rates, production of hydroelectric energy, of storage volumes and of

Page 148/214 LNEC – Proc.605/1/11926 the concentration of various elements that affect the quality of water, in any given point in space or time.

7.2.3 Structure of the system

The IRAS program simulates a representation in the shape of a grid that consists of nodal points and arcs, of a system of water resources. The grid of nodal points and arcs may represent various components of any given system with inter-arcs representing surface water and underground water. These grids may contain nodal points for storage or without storage, sections of rivers with unidirectional or bidirectional discharge, or transference of water. This model can furthermore simulate in time, in order to estimate the ranges of flow volumes, storage volumes, electricity production and consumption levels, and the concentration of factors that influence the quality of water and that may result in a system with a given configuration, assuming the parameters for the project, the operational conventions , the hydrological input data, and the residual flow volumes after the various uses.

A system like the hydrographic basin of the Cunene River represents a main river with a certain number of tributaries, it has centers of consumption of greater or lesser importance like for instance towns or villages, and it has lakes or dams. Some centers of consumption extract water from dams and may or may not restore water to the system. At other locations, the water may pass through hydroelectric plants for the production of electricity and pressure. All along the basin some water is consumed and other [water] may leave the system.

A selected physical system can be represented in different manners by a grid of nodal points and arcs. For example, to supply a town there may be a catchment, with a contributor like for instance an aqueduct in the form of a canal or conduit, whereby the town is represented as a consumption nodal point at the extremity of an arc. The same result would be obtained by considering just one discharge point from a dam to supply a town, dispensing one nodal point and one arc.

One nodal point may be a combination of various types of nodal points as described above. For example, a dam may have multiple arcs representing inflows and

Page 149/214 LNEC – Proc.605/1/11926 outflows, and can also serve as a hydrometric station and as a discharge point for residual water. A lake differs from a dam in as far as their effluences are controlled, as they are in this case determined by the topography of the banks of the lake and, consequently, they are in effect of the volume and the benchmarks of the surface of the water. On the other hand, the effluences and discharges of a dam are based on, or determined by, rules for the operation of the hydraulic outfit that controls the dam. The rules for operation specify the flow volumes that are to be discharged, the volumes that are to be stored, for any given available volume, for requirements downstream, and for the month of the year.

The aquifers can be confined or not confined, and can be distributed horizontally and/or vertically (i.e. in multiple layers). The humid zones (or very level areas) can be defined before the simulation as regions where the direction of discharge is not known.

In any nodal point the conservation of the mass is guaranteed for each phase of the simulation.

The discharges between geographical locales (nodal points) are represented by the arcs. The arcs between two nodal points may be unidirectional or bidirectional. The unidirectional arcs may represent: - river sections that link two nodal points of surface water; - derivation canals, channels or conduits that link any given two nodal points that are neither aquifers nor humid zones.

Bidirectional arcs may represent water transference, in any direction, between two nodal points. All arcs that are linked to aquifers and/or humid zones are bi- directional. Any arc, whether unidirectional or bidirectional, may be linked to a derivation arc. The derivations represent canals or constructed aqueducts that are consequently of an artificial nature.

The physical properties and the rules for performance that govern the quantities and the directions of the water flow in each derivation arc have to be specified by the user.

Page 150/214 LNEC – Proc.605/1/11926 The hydroelectric plants and/or pumping stations can be linked to any arc. The hydroelectric plants may present fixed or variable rates, if the nodal points upstream or downstream [from them] are dams. The rates for electricity and pressure production are calculated as being the difference between the charges upstream and downstream, or between the water quotas upstream and downstream of the turbine, whereby the lower of the two is chosen. If the difference should be negative, it is assumed that electricity consumption for pumping will have to be taken into account.

The electricity that is consumed by the pumping process can be assessed only by the arcs that are defined as pumping stations. This electricity matches the quotas for each nodal point at the extremities of the arc.

The operations of storage by means of pumping can be simulated if a hydroelectric plant is defined as a unidirectional arc between two nodal points, and a pumping station is defined as an arc that is also unidirectional, but in the opposite direction between the same two nodal points. One could just as well use a bidirectional arc.

7.2.4 Input data for the system

The [input] data for the system include the name of the system and the number and duration (in days) of the periods that are less than one year. The period of time for each application needs to be defined in order to represent the variations of the various parameters for the system as regards the water resources being analyzed. Up to 60 periods of simulation of less than a year can be defined. Their duration (number of days) does not have to be identical.

Once the durations of the periods that are less than a year have been defined, the number of simulation sequence contained in each period can be specified. Each computation sequence requires an equal duration from a given period of analysis in the year that has been adopted by the system. It is necessary to have a minimum of twelve computation sequences for each period of analysis of the year. This period is equal for each of the years of simulation. There is no maximum limit.

Page 151/214 LNEC – Proc.605/1/11926 One or more sequences of time cycles can be defined for each hydrometric station. The user may select any number of years for simulation purposes. If the number of years for simulation is higher than the number of years of the station‟s existence, a repetition will take place of the cycles by simulation.

As the nodal points might represent very different types of physical entities it is necessary to provide common data for all nodal points and there are specific requirements for each type.

For all nodal points it is necessary to define its name, the multiplication factor for the discharge of a hydrometric station that serves as a reference, the parameters as regards quality, and quotas for reference and shrinkage rates.

Each nodal point has a name. For each nodal point that was not identified by a name, an automatic name will be given that includes the letter N, followed by the number of the nodal point.

It is necessary to define the absolute or relative quotas for each nodal point if there are arcs involving electricity production or pumping. If the nodal point is one of storage then the rates of storage-quotas must be defined.

The rates of shrinkage that correspond to evaporation or infiltration need also to be specified for each of the nodal points. Both may correspond to losses for the system. However, losses by infiltration may correspond to transference of water from surface water to underground water, or between aquifers. In this case there has to be an arc between two nodal points.

The various data for the nodal points are the following: a) Definition of the attribution for the effluence of a nodal point for one arc and consumption rates b) Requirements at the nodal points and multiplication coefficients for the flow volumes c) Data for a nodal point representing a dam d) Data for a nodal point representing a natural lake e) Data for nodal points representing either aquifers or humid zones f) Data for hydrometric stations and flow volume reports g) Nodal points representing the discharge of residual water and discharge reports.

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In parallel with those for the nodal points, the data for the arcs have specific requirements in accordance with their types.

The only common requisite for each arc is the name. Similar to the nodal points, if a name was not specified it will be provided by default.

The various data for the arcs are the following: a) Data for arcs emanating from superficial water b) Data for arcs emanating from aquifers and humid zones c) Data for arcs emanating from hydroelectric or pumping stations d) Data for derivation arcs e) Data for arcs with auxiliary requirements f) Data for bidirectional arcs

7.2.5 Operating conventions for the system

Operating conventions are necessary in order to define the choices that have to be made. They include the sites with dams where the [types of] distributions have to be specified, for the nodal points where water may be distributed via various arcs or for the nodal points with outflows toward a derivation arc, and for those wells where pumping may take place, either for purposes of extraction or for artificial recharging of aquifers. The decisions as regards the way in which the water is to be conveyed from a determined point of the system, during each phase of computation, can be based on the water requirements at various consumption points or on the requirements that have been defined, and finally, on the water that is available at this [particular] point.

The rules for operation can be based solely on the information on available water and requirements, without considering the shortfalls. Rules that are based on water availability can be modified in order to allow operating conventions that also take the shortfalls in supply and requirements into account.

In this program, the nodal points are indicated by the letter n, the arcs by the letter l, the episodes of analyses during the year by the letter t, and the computation sequence by the letters tt.

Page 153/214 LNEC – Proc.605/1/11926 The rules for the supply of water from independent dams may be specified by the user. These operation rules are based on a number of zones that are defined by the user, for each period of analysis within the year t chosen. Each storage zone z includes a range of stored volumes. For each of the zones – with a maximum of 7 – the user has to define the minimum and maximum volumes as well as the volumes at the beginning and end of period t, respectively. It is also necessary to specify the water supply from each zone, linked to the minimum and maximum stored volumes in zone z at the beginning and the end of period t.

The four last rates above cannot be negative, which is the sole restriction that applies. These four rates can also be constants. In most cases the rules for operation specify a constant water supply for each zone, reducing the rates by zone of supply to lower quotas.

For some dams that are operated jointly the operation conventions will depend on the total volume of that [particular] group of dams. As a rule of thumb, the rules may be laid down by the dam [that is situated furthest] downstream.

The rules that have been described above are based on the availability of water. The effluences of a dam may also been based on the deficit of the requirements for the nodal points in question. These outflows require the consideration of the remaining period in the year if one deducts the period of analysis, and of the multipliers of the flow volumes of the inflows to the dam. There is no guarantee that this effluence may be suitable. Each multiplier for a flow volume for a necessity deficit can vary for each period of analysis in the year in question, but can also vary from one year to the next. There may be several multipliers for discharges in places with requirements that are associated to the same source dam.

Each unidirectional derivation arc of a grid links a locale with available water to a site where water is required. For each nodal point where there is an effluence towards a derivation arc, an attribution function for each period of analysis in that year has to be defined. This function defines which part of the effluence of a nodal point may be deviated into the arc after the requirements of the arc have been satisfied.

Page 154/214 LNEC – Proc.605/1/11926 Directional derivation arcs can also be designated as requirement arcs. In these arcs, at their upstream extremity, the water enters that is necessary to satisfy existing deficits at the nodal points [that are situated] downstream. Under these conditions, the water that is necessary to cover the deficit enters at the upstream nodal point, discounting the input of natural water. This deficit is the deficit that has been accumulated less the expected inflow, less anticipated inflow and divided by the total number of computation sequences for the period of analysis during the year.

These discharge increments which cover the requirements have priority status over the attributions of water that are based on the availability monitored by the effluent arcs. If there is not enough water to satisfy all requirements in multiple derivation arcs of one single nodal point, the water that is available is distributed according to the [hierarchy of the] nodal points as defined in the grid, indicated by the numbering of the arcs.

As regards the water that is discharged by or via aquifers from another nodal point, IRAS assumes that it is conveyed by means of underground arcs. In surface nodal points the transference of underground water may represent the physical, natural processes or a pumping process. The pumping processes that are part of a bidirectional arc can be specified as depending on the quantities of available water vs. the masses of water that are represented by the nodal points at both extremities of the arc.

7.2.6 The simulation sequence

Simulation by IRAS takes place in a module that is separate from the program and that does not have a graphic interface. The results of the simulation can later be visualized on a terminal, if that is desired, or used as data for calculation sheets for further analyses.

The results of the simulations are the values of the volumes that were stored at the beginning and at the end, the average flow volumes, expressed in the units as defined by the user. Finally, functions can be calculated and visualized that are defined by the user, of these variables, and statistical analyses can be carried out.

Page 155/214 LNEC – Proc.605/1/11926 The IRAS program simulates a system in each of a series of computation sequences. Before each simulation, the user needs to specify the number of years, the number and the periods to be analyzed in the year in which the year is to be split up, whereby these episodes do not all have to be of equal length, and the number of times the calculation process has to be applied to each of the periods of analysis for the year. A day is the smallest possible duration of a period that is smaller than one year. It is also possible to carry out simulations where the total period of simulation is a computation of all the periods to be analyzed for that year, and is [still] less than a year.

If the number of years of the dossier containing the flow volume data is less than the number of years of the simulation, the introduction of the flow volumes will be repeated as often as necessary in order to complete the total number of years for the simulation. In the case of concentrations of discharge of residual water, the rates of the last year of the dossier in question shall be repeated until the total number of years is made up.

A sequence of the simulation involves various steps or cycles of the components of the system and uses various series of data. The most important of these data would be the series of flow volumes, the periods that are considered for the simulation, and the grid of nodal points and arcs. The simulation begins by identifying a series of flow rates. For each of the series (or replications), the simulation moves to the sequence of successive periods of the year that are to be analyzed, for each of the years. In each period of analysis for the year, the simulation proceeds through each step of the calculation.

Each step of calculation during the simulation of the grid contains 5 calculation cycles.

The 1st calculation cycle includes the estimates for natural recharge of the nodal points representing the aquifers and humid zones, and the losses by evaporation and, if applicable, the infiltration for each nodal point on the grid. These losses at each nodal point are based on the volume of stored water at the nodal point in question. In this manner, the volume of the nodal point will be reduced by the total anticipated shrinkage.

Page 156/214 LNEC – Proc.605/1/11926 The predetermined inflows of water from dams (that are not necessarily the actual water supplies that are going to be implemented) are also estimated for all the dams having effluences and that would be dependent on the respective conventions for operation or storage. These rules depend on the volumes that are stored. The supply that is to be realized depends also on the deficits between the forecasted requirements and the minimum supply, if applicable.

The first part of the 2nd calculation cycle of the grid relates to the unidirectional discharge of the arcs. In this step the uncontrollable increments of the affluences of surface water are calculated, where applicable.

The second part of the 2nd calculation cycle follows the direction of discharge and computes the affluences for each nodal point that represents surface water, where applicable.

After that, the affluences (or effluences) of each bidirectional arc are added (or subtracted) from the water that is available at that [particular] nodal point. Each discharge of a bidirectional arc is based on the volume of water that is stored or of the water that exists at each of the extremities of the arc. In this way these bidirectional discharges can cause an increase or a decrease of the available water at the nodal points at the extremities of the arc.

During the third part of the 2nd cycle the effluences of the nodal points are assessed. If there is no storage at this nodal point, the water that is available at this node is considered as an effluent. If storage takes place, the effluence from this nodal point is based on the operation conventions that apply to this node.

If any consumption takes place at this nodal point, this shall be based on the consumption factors that were defined by the user. The consumed water is lost by the system. The remaining discharge, after consumption, will be released into the effluences of the unidirectional arcs.

Finally, during the 2nd calculation cycle, the effluences of unidirectional arcs are estimated, based on the inflows of the arcs and the storage volume in question, if

Page 157/214 LNEC – Proc.605/1/11926 applicable. The volumes of the arcs are calculated when a propagation of flow volumes is employed. If electricity is produced or pumping takes place at an arc, then the produced electricity or its consumption is based on the inflows of the arcs and the storage charge at the nodal points that are situated upstream and downstream. The effluences of the arc may be influenced by the propagation of flow volumes and by evaporation and infiltration, should these occur.

The 3rd calculation cycle is carried out in each of the bidirectional arcs. The discharges at these arcs are based on the volumes that are stored at the respective nodal points representing aquifers and underground water and/or humid zones. In a similar vein, if bidirectional arcs were defined for the production of hydroelectric energy and/or pumping, the electricity that was produced or consumed is calculated.

The 4th calculation cycle corresponds to the volume that is stored at each of the nodal points representing aquifers/underground water or humid zones, taking the affluence or effluence for each arc into account that gets to each arc or runs off through it from or to one of these two types of nodal points. This 4th calculation cycle completes the simulation for each step of the calculation.

Once one step has been calculated, the simulation proceeds to the next step. This simulation process continues until the end of the period to be analyzed for [within] the year. At the end of this period the final storage volumes, the average discharge rates over the period, the electricity, the pressure, and the concentrations of water quality for each nodal point and each arc are calculated and filed in a dossier containing all [these] results for future visualization or analysis.

7.2.7 Simulation procedures, methods and hypotheses

As mentioned previously, the units of discharge and volumes, of the data and results, are defined by the user of the program. The units of flow volumes that are used for the simulation program are expressed in the units as defined by the volumes for storage, divided by the calculation step. The more detailed presentation of the simulation processes is based on the above-mentioned units of flow volumes that

Page 158/214 LNEC – Proc.605/1/11926 generally do not correspond to the input and output units. Any of these units can be defined by the user of the program.

The nodal points for the storage of surface water are subject to losses by means of evaporation and infiltration. The nodes for underground water/aquifers are only subject to shrinkage by infiltration. These losses correspond to losses of water by the system.

The shrinkage is calculated on the basis of the quota of water-storage volume, or storage volume-surface area of the water, and the daily evaporation rates, and depending on the daily rates of infiltration, as defined by the user.

During each episode tt that is simulated, the simulation process of IRAS includes the calculation of an increment to the natural inflow, if the nodal point relates to surface water, the natural recharge, if the node n represents an aquifer. In order to calculate the increments of the inflows of the nodal points, it is necessary to calculate the natural discharges of these nodes.

The natural flow volumes are not controlled, in each nodal point during the calculation step tt they are the sum of all the average flow volumes in the hydrometric stations g during the period of analysis of the year t, adjusted for the duration of the calculation step tt.

The incremental flow volume, be it “natural” or uncontrolled, is the difference between this uncontrolled flow volume of the nodal point n and the sum of the uncontrolled flow volumes at each of the nodes that is situated upstream at the nodal points m, that emit unidirectional arcs (and that are not derivations) and that link up with node n. Should no nodal points exist upstream from node n then this node n is the initial nodal point of the river. In this case the incremental flow volume is equal to the natural uncontrolled flow volume at this location.

These natural incremental flow volumes may be negative. Should they be negative, they would reflect the losses through natural discharge due to evaporation and infiltration, or even derivations that have not been taken into account for the simulation.

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The water that enters into each nodal point without storage during each phase of the calculation is either consumed or flows out from this node during this same phase of calculation. Thus the outflows of a nodal point without storage are equal to the respective inflows, less consumption.

The water supply from dams is defined by the user.

As the outflow of a nodal point with storage n is determined, the volume for final storage may be calculated by the equation for bulk conservation. This takes into account the initial volume, the useable inflow, the losses and outflows, in one and the same step of calculation.

The procedures for propagation of flow volumes can be implemented at the level of the unidirectional arcs. These procedures have to be implemented when the time of passage of the water is more important than the duration of the period of the year that is to be simulated.

The users of IRAS can introduce a hydroelectric plant on any arc. If such a station is situated on an arc, all inflows are useful for the production of electricity. The water pressure and electricity are produced during each phase of the calculation of a charge (quota) from a higher to a lower charge. After the average daily electricity and water pressure rates have been calculated, they are included in the results for each period of analysis for the year that was selected for calculation purposes.

The electricity that is generated and the available water pressure at a hydroelectric plant on arc l at the beginning of each calculation phase tt, depends on some data that are defined by the user. These data include: - the capacity of the plant (associated to the nominal charge and to discharge rates); - the charge, between the quota upstream and the quota of the turbine, or of restitution; - the factor of the station (fraction of the daily electricity production); - the minimum flow volume for the production of electricity;

Page 160/214 LNEC – Proc.605/1/11926 - the constants for the production of electricity.

The electricity can only be produced by stations on the arcs of surface water when there is a flow volume that exceeds the minimum, and if the charge is higher than 0.

Pumping stations may be situated on any arc. Pumping can take place on arcs of underground water if boreholes or artificial recharges are implemented on this arc. The only reason to design a pumping arc is to calculate and to record the electricity that is consumed in association with the pumping [process], and the respective negative useful charge. At each nodal point at the extremities of this arc the charge or quota must be indicated. The volume that is pumped, or the water volume, on each bi-directional arc is determined by the user and depends on the volumes that are stored or on the quantities of water that is available at the nodes at the extremities of the arc.

7.3 Results of simulations

7.3.1 Introduction

During the simulation process and according to the user‟s choice, the values of all variables can be sent into a file that is to contain the results, to a monitor, or directly to a printer. After the simulation process, the file that contains the results can be inspected, printed or copied to a calculation sheet. All these options will increase the time of simulation. The main objective of the IRAS program is dedicated to the simulation and to create unformatted files with results. These files, as all results, can be used by the part of the IRAS program that is dedicated to the presentation of the simulation results.

The options for presentation of the results include tables with the values of the results, color-coded animated sequences portraying the grid of nodal points/arcs or a geographic representation of the system, graphs on the temporal series of the values of the variables (or up to 6 functions of these variables as defined by the user), and probability projections of the duration of deficiencies in the system and their extent.

Page 161/214 LNEC – Proc.605/1/11926 The simulation processes an enormous amount of data, that relate to individual or multiple flow sequences, including the volumes that are stored, consumption and shrinkage, the concentration of elements for water quality, the production of hydroelectric energy and the consumption of pumps, at many locations and for multiple episodes.

The examination of all these results, even using the capacities that are available in IRAS for the presentation of interactive graphs portraying the temporal series or tables, can take up an excessive amount of time. It is not necessary to examine all the results that were obtained, but to know when and where the system is in need, and to choose some data from these critical periods.

The choice of the option of visualization with color-coding allows easy indication of periods in which the performance of the system is not satisfactory. This information helps to concentrate on the quest for defects in the system.

7.3.2 Perimeters and zones

For visualization by means of color-coding it is necessary to define the perimeters that are linked to each variable that is of interest. These two values divide the range of possible values for each simulated variable into three zones: the lower, medium and upper zones. These zones of values of the variables take on different meanings, depending on the type of variable and on its interest for the user.

The defined perimeters of the values do not affect the simulation. They just divide the values of any given variable into three ranges or zones that correspond to what the user considers satisfactory, to ringing an alarm bell or to a breakdown of the expected conditions. The satisfactory zone is represented by the color green, the alarm by yellow and breakdown by red. There are six options that result from the combinations of the colors and the order of same as regards the upper, medium or lower zones.

7.3.3. Diagrams expressed in terms of time and space

The users have many options to present some or all the values of the simulated variables in terms of time progressions for any nodal point or arc, or according to a

Page 162/214 LNEC – Proc.605/1/11926 spatial sequence at any point in time. At any given time up to four diagrams can be presented with simple or multiple variables.

The diagrams of a temporal nature can contain simple or multiple variables in one graph. The spatial diagrams have as their horizontal axis the sequence of the arcs or nodal points. From the sequence of figures in one single graph one can get an idea of the dispersion or concentration of the values that a variable derives from a particular point in space and time.

The user can define a function of a variable and visualize the values of this function as a series in time or space. Examples of this function can be the economic benefits or disadvantages, or squared deviations of desired objectives, or just hierarchic functions that show the degrees of satisfaction or non-satisfaction.

7.3.4 Dynamic images of the system in relation to time

If the outer limits of the values are defined the user can opt for the visualization of a dynamic succession of images that show the variation in time of the values of the variables. Each image shows each nodal point or arc (or its geographic representation) with a green, yellow or red colour.

In the case of simulation of multiple variables for each node or arc, for which perimeters were set, it is necessary to establish a priority for the visualization of the color. If some of the variables correspond to the color red, this will be shown. The same applies if one of them corresponds to yellow and no red is involved, whereby the yellow takes precedence over the green. This color will only appear if all the variables are in the same zone. When there is no definition of perimeters the color is green for all situations.

When yellows or reds appear in an image, the locations in question can be analyzed by means of a series of temporal or spatial graphs, with the aim to find the causes of the appearance of the colors in question, and what could be done in order to provoke circumstances that may cause such situations. The user is not required to examine all the results of the simulation in order to determine if the system has satisfied the expected objectives.

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7.3.5 Presentation of statistics

Over and above the diagrams that portray temporal and spatial series, the statistical information can be presented by images that are similar to those mentioned above, that include the reliability and resilience of all variables that were qualified by the definition of perimeters.

The credibility of a given variable is the probability that its value is situated in the satisfactory (green) zone, or in the satisfactory (green) and warning (yellow) zones, as defined by the user. In this way there is a “green reliability” and a “yellow reliability”. In both cases the average values for each period of analysis pertaining to the year of simulation are used. These reliabilities are defined as follows: “Green Reliability” = 1.0 - (number of values in the yellow and red zones/number of periods of time simulated) “Yellow Reliability” = 1.0 – (number of values in the yellow zone/number of periods of time simulated)

There are usually less instances of green reliability than there are of yellow reliability. Should they be equal in number, this means that there are no “yellow” events; there are only “green” events and possibly [some] “red”, when the red zone is adjacent to the green zone.

Resilience is a means of recuperation of one variable from one zone to the next. It is likely that, during the following calculation cycle, the value of the variable moves into the next more favorable zone. As there are two limiting values, there are also two resiliencies for each simulated variable, just like there are two reliabilities. “Red Resilience” = 1.0 – (number of periods in which the values in the red zone are followed by values in the yellow or green/number of values in the red zone) “Yellow Resilience” = 1.0 – (number of periods in which the values in the yellow zone are followed by values in the green zone/number of values in the yellow zone)

Page 164/214 LNEC – Proc.605/1/11926 If there are no values in the red zone, than the Yellow Reliability corresponds to 1 and the Red Resilience is not defined. If there are no values in the yellow zone, then the Green Reliability corresponds to the Yellow Reliability and the Red Resilience is not defined.

In the case where the perimeter values have not been defined for any given variable the average reliability and resilience cannot be defined.

7.3.6 Probability projections

The distribution of probabilities of the indicators of resilience and vulnerability can also be shown by means of images. The allocation of probability of resilience indicates the probability of various continuous sequences with unsatisfactory values (in the red or yellow zones). The distribution of probability of vulnerability indicates the probability of the concentration of unsatisfactory values (deviations in relation to the value(s) that exceed(s) the limits of the green zone). Both allocations can be shown as unconditional or conditional probabilities, in the form of histograms.

Probability projections on resilience indicate the probabilities of the various durations being situated in the yellow or red zones. The duration (number of episodes analyzed within the year) of a sequence of values in the red zone starts when the sequence has entered a red zone after having been located in the green or yellow zones, and it ends when the sequence leaves the red zones and enters the yellow or green zones. In the case of the yellow zone being adjacent to the red zone, the duration of the sequence of the values in the red zone begins when the sequence of values exits the green zone and enters the yellow or red, and it ends when the sequence of values in the yellow or red enters the green zone. The sequences of the values in the yellow zone include those parts that are in the red zones (adjacent to the yellow zones) before they enter the green zone.

The projections of probability of vulnerability indicate the probability of the different extensions of unsatisfactory values (from the yellow or red zones). The distributions of probabilities of yellow vulnerability show the probabilities of the absolute differences between the values of the variables in the yellow zone (the adjacent red

Page 165/214 LNEC – Proc.605/1/11926 zone if applicable) and the boundary or limits to values that separate the green and yellow zones. The allocations of probability of red vulnerability show the probabilities of absolute differences between the values of the variables that are situated in the red zone and the values at the closest boundary (limitation values) that separate the red zone from the yellow or green.

Cumulative histograms on the probability of vulnerability can be generated for the users who are interested in the probabilities of the sums of all deviations from satisfactory values. These histograms show the probabilities of the sum totals of the absolute deviations in the red or yellow zones from the next closest boundary of the green zone. If, during a series of unsatisfactory values, some of these values are situated in the red zone, the histogram will stay red. If all values are situated in the yellow zone the histogram will show the color yellow.

The projection of probabilities, be it of resilience or of vulnerability, can be shown by means of unconditional or conditional distributions. The unconditional distributions take into account the average values for the periods being analyzed for the year of the simulation, whilst the conditional distributions only take the values into account that are situated in the yellow or red zones. The duration of unsatisfactory values (for the histograms on resilience) and the extensions of the unsatisfactory values (for the histograms on vulnerability) are divided into 10 distinct scales, taking the maximum duration and extent into account that was encountered during the simulation. The user can change the dimensions of these distinct scales, should he so wish.

7.3.7 Dossier containing unsatisfactory events and tables

Should the user wish, a file can be created that contains the selected events, nodal points and arcs with yellow and red color coding.

The data in this dossier is divided into various sections. Each section corresponds to a specific nodal point or arc and for a specific variable, for which specific values have been defined. The data contained in the title of the section include the names of the system, of the files on flow volumes and discharge of residual water, the date and the period, the designation of the variable and of the node or arc, the type of

Page 166/214 LNEC – Proc.605/1/11926 perimeter and the sequence of colors (one of the six alternatives). For each calculation cycle with the occurrence of a value in yellow or red, the number of “events” is recorded, the number of replication of flow volume, the year, the period of analysis within the year, the value of the variable, the perimeters, and the absolute deviation from the limit for a satisfactory value. Summaries are also supplied, stating the duration of the unsatisfactory events, the accumulated extensions, the number and the probabilities of the events in the yellow and red zones.

7.4 Definition of the Cunene River System

7.4.1 Introduction

The system of the Cunene River that was to be simulated by IRAS was limited in respect of the quantity of water. As a matter of fact, in spite of the fact that it cannot be stated that there would be no problem with the quality of the water, the lesser importance that is attributed to the problems of water quality has led to the consideration that a more adequate approach in the initial phase would be just to calculate the quantity of water.

The system of the Cunene River, just like any other river where the planning for utilization of water resources are to be carried out, is not a static entity, it rather undergoes an evolution in the course of time, which means that one needs to look at a successive adaptation of the water supply that varies in the course of time. As a consequence, various systems are defined, starting with a system for reference purposes, and introducing successive changes in order to look at various objectives, sequences or alternatives.

Initially a basic grid was defined for the Cunene River, which corresponds to the actual situation of the basin. Subsequently additional systems were defined, that were constructed by means of the introduction of variants that complied with two criteria. One of the criteria was to define alternative systems, based on previous definitions of plans for the Cunene River Basin. Another criterion is the introduction of the necessary components for solving the problems with supplies that were encountered during

Page 167/214 LNEC – Proc.605/1/11926 previous simulations. The choice of these criteria was made depending on the simulations that had been carried out and the definitions of alternative scenarios.

The definition of systems is carried out by the construction of the grids of nodal points and arcs. Its relative location is made as far as possible in accordance with the geographic situation, in order to allow quick identification of the correspondence between the graphic representation of the system and physical reality on the ground.

7.4.2 Definition of the initial system (CuneneA)

The IRAS program assumes that the first nodal point is the one that is furthest upstream. From that point, and with the objective of following the course of the water, the other nodes were identified by means of unidirectional arcs.

Figure 31 presents the initial system for the Cunene River that was the object of the first simulations. The identification of the various components is made in the following tables.

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[dot with circle = nodal point of a sub-system circle with 4 exits = hydrometric station black square = dam small circle = points of urban consumption] Figure 31 – Initial schema of the Cunene River for purposes of simulation by IRAS

Page 169/214 LNEC – Proc.605/1/11926 Table 12 – Hydrometric stations

For the nodal points that represent hydrographic stations the flow volumes for surface water are known. These data are essential for the simulation; they are linked to a file that is dedicated to them, with the sequence of monthly average flow volumes, the period of analysis into which the year was divided for the [purposes of] simulation of the Cunene River.

The majority of nodal points reflecting urban areas that require supply correspond to a population, or in some cases a group of populations, as the geographic proximity would justify. To each of the nodes under investigation consumption [rates] are linked. It was also taken into account that the arcs that are directed at the urban areas are deviations.

Page 170/214 LNEC – Proc.605/1/11926 For the initial system only the existing dams were taken into consideration, of which there were four. For each dam it was necessary to establish a set of data, like the table of the areas and the flood volumes and the conventions for operation.

Table 13 – Urban areas to be supplied

Page 171/214 LNEC – Proc.605/1/11926 Table 14 – Dams on the Cunene River

In the initial system the perimeters for irrigation were not introduced. This option only intends to analyze the supply [of water] to the populations, beyond the insertion of a deviation towards Namibia, which is multi-purpose of nature. On the other hand, the system already reached saturation of its capacity that is, as mentioned above, a maximum of 60 nodes and 60 arcs.

To summarize, the initial system for the Cunene just served to test the capacity of the IRAS program, and the simulations that were carried out [during this phase] may be considered as trivial. It should be seen as an analysis for reference purposes, in preparation of the simulations that are more interesting for the purposes of planning.

7.4.3 Strategies for the supply of water resources from the Cunene

Once the behavior of the IRAS program had been verified for the initial system, strategies for the supply of water resources were defined, allowing for new infrastructures, whereby those that had been anticipated in previous Plans were prioritized. One with the highest priority is the Epupa project for which a recent viability study exists. For this it would have been very useful to have access to the data on this scheme in order to incorporate it into the various alternative schemes for the Cunene River.

The order of simulation of the various alternatives was not rigid as it was defined on the basis of the results that were obtained during prior simulations.

The hierarchy of utilizations was defined at the start. In the first place there is the supply of water to people. As far as the following priorities were concerned there were already several alternatives. Two of these were of major importance: either the use in

Page 172/214 LNEC – Proc.605/1/11926 Angola would receive preference in accordance with the criteria for the allocation of water, or preferentiality would be given to the export of water to Namibia. The final choice between these two criteria is highly political. From a technical point of view it was deemed advantageous to simulate both alternatives.

8. SIMULATIONS OF THE HYDROGRAPHIC BASIN OF THE CUNENE RIVER

8.1 Definition of methods

8.1.1 Definition of the second Cunene River System (CuneneB0)

Figure 32 portrays the second system of the Cunene River. The identification of the various components can be found in the following tables.

In this system, only 13 out of the 22 hydrometric stations that were used for the initial system were considered. This reduction results from the fact that some of the stations are quite close to each other, and that there was only little information available for some stations. Table 15 lists the hydrometric stations that were [ultimately] taken into account.

Table 15 – Hydrometric stations on the second system

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[dot with circle = nodal point of a sub-system circle with 4 exits = hydrometric station black square = dam small circle with D = points of consumption small circle = other nodal points] Figure 32 – Second system of the Cunene River for purposes of simulation by IRAS

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The nodal points for the remaining 9 hydrometric stations continue to exist, but no input data is introduced for these; therefore they can just serve for checking the results that are obtained.

The number of populations or complexes of populations that are to be supplied by the second system is far less than for the initial system, reduced from 28 to only 4 nodes, as listed in Table 16.

Only the population groups with significant consumption figures were retained when comparing the availability of surface water in their immediate vicinity. As a matter of fact, most of the other populations show rather negligible consumption figures if one compares them with the available resources during each year.

Table 16 – Urban areas to be supplied in the second system

For the second system the four existing dams were not taken into account, which are listed in Table 17. For each dam there was just an analysis of the circulating flow volumes, which corresponded to the initial state of the basin, before human intervention.

Table 17 – Dams on the Cunene River

Page 175/214 LNEC – Proc.605/1/11926 Two perimeters for irrigation were already introduced into the second system, see Table 18. This option corresponds to a situation that is almost equal to reality, or maybe more precisely to a situation that the system would have generated, if more irrigation had been implemented than has been the case.

Table 18 – Irrigation perimeters on the Cunene River

The system that was described and that includes some of the supply points for the population and only two irrigation perimeters, arrived at half of the saturation capacity of the IRAS program, allowing the inclusion if necessary of more supply points for consumption, and of more water storage facilities.

In summary, the second system helped to analyze the influence [of the introduction] of irrigation on the utilization of the water from the Cunene River. It also corresponds to an analysis for reference purposes that can be compared with other systems that consume more water, and that require major control of the water as a result.

8.1.2 Definition of the third Cunene River System (CuneneB1)

Figure 33 represents the third system of the Cunene River. Identification of the various components can be found in the following tables.

In this system the 13 hydrometric stations are still used that are listed in Table 15, as well as the population groups as mentioned in Table 16, as well as the existing dams that appear in Table 17.

The main difference is the inclusion of two of the irrigation perimeters, those of Matala and Humbe, and of the Gove Dam.

Page 176/214 LNEC – Proc.605/1/11926 In summary, the third system for the Cunene helped to analyze the possibilities of simulation of irrigation in the utilization of water from the Cunene River, without having recourse to the construction of new supplies. The fact that it was impossible to guarantee irrigation or to supply water to Namibia, compliant with the International Accord, gave rise to the definition of the requirement of new supplies.

8.1.3 Definition of the other Cunene River Systems (CuneneB2 to CuneneB5)

Figures 34 to 37 portray the other systems for the Cunene River. The identification of the various components can be found in the following Tables.

For all of the irrigation perimeters the basic hypothesis was taken into account that they would have recourse to direct extraction from the Cunene River, without necessitating other regularization works. In order to test the capacity of the system 7 nodal points for the agricultural areas were established, that are detailed in Table 19.

Table 19 – Irrigation perimeters requiring supply

For each irrigation perimeter that was designed according to a numbering sequence used by Castanheira Diniz, different areas and different crops were examined in order to assess the various consumption rates, representing different scenarios for development.

In these systems the various supplies were increased one at a time (irrigation in all the perimeters and production of hydroelectric energy at Matala and Ruacana in system Cunene B2, Jamba-ia-Oma in system Cunene B3, Jamba-ia-Mina in system

Page 177/214 LNEC – Proc.605/1/11926 CuneneB4, both with production of electricity and Cova de Leão and Catembulo in system CuneneB5) in order to increase water security within the system.

The possible combinations are manifold, and it is not possible to carry out a simulation of all combinations. The choices made were always based on the results of prior simulations. However, nothing gets in the way of other, future simulations in order to cover further situations that may be considered to be more plausible, faced with new premises.

8.2 Entry data for simulation by IRAS

8.2.1 Simulation periods

The time period for each application was defined in order to represent the variations to the various parameters for the system of water resources under analysis. As up to 60 simulation periods with a duration of less than a year can be defined, 12 periods were chosen that correspond to the months. Their durations (number of days) did not necessarily have to be the same, and for this reason the respective (number of days) for each month were adopted, 31 days for January, March, May, July, August, October and December, 30 days for April, June, September and November and 28 days for February. This distribution results in an error of one day every four years (as the month of February has 29 days in leap years), which is a trifling error within the context of this work.

The time series for each hydrometric station were determined based on studies on available surface water.

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[dot with circle = nodal point of a sub-system circle with 4 exits = hydrometric station black square = dam small circle with D = points of consumption small circle = other nodal points] Figure 33 – Third system of the Cunene River for purposes of simulation by IRAS

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[dot with circle = nodal point of a sub-system circle with 4 exits = hydrometric station black square = dam small circle with D = points of consumption small circle = other nodal points] Figure 34 – System CuneneB2 for purposes of simulation by IRAS

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[dot with circle = nodal point of a sub-system circle with 4 exits = hydrometric station black square = dam small circle with D = points of consumption small circle = other nodal points] Figure 35 – System CuneneB3 for purposes of simulation by IRAS

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[dot with circle = nodal point of a sub-system circle with 4 exits = hydrometric station black square = dam small circle with D = points of consumption small circle = other nodal points] Figure 36 – System CuneneB4 for purposes of simulation by IRAS

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[dot with circle = nodal point of a sub-system circle with 4 exits = hydrometric station black square = dam small circle with D = points of consumption small circle = other nodal points] Figure 37 – System CuneneB5 for purposes of simulation by IRAS

Page 183/214 LNEC – Proc.605/1/11926 Table 20 – Consumption in the urban areas of the CuneneA system

Table 21 – Consumption in the urban areas of the CuneneB0 system and subsequent systems

Page 184/214 LNEC – Proc.605/1/11926 8.2.2 Data for the nodal points

All important nodes were labeled as indicated in Tables 20 to 31. Other nodal points where the name was not important were automatically labeled by the program with a name that started with the letter N, followed by the number of the nodal point which will appear in the results. Constants or monthly consumption figures for the population where taken into account during the simulation. Tables 20 and 21 portray the values that were used. Only the absolute quota for the nodal points were defined where an arc was situated that included electricity production or pumping, those that corresponded respectively to the supply of hydroelectric power or to extraction points for irrigation purposes. For the nodal points corresponding to storage, which relate to dams, the functions storage-quotas were defined. Only evaporation was considered as regards the shrinkage function; it was only specified for some of the nodes, namely those that corresponded to dams. Losses by infiltration were not taken into account because of the difficulty to obtain data that would allow verification of the validity of the simulations. For the nodes relating to surface water that serve as inflows for various arcs that transport the water from this nodal point to other surface water nodes, or for the cases where one single arc is defined as a unidirectional derivation, functions for the attribution of water towards the arcs were defined.

The definition of the attributes of the nodal points was made by means of a standard table (example for nodal point N18 of the system CuneneA):

Attributed to Outflow of node 18 Arc 12 Arc 35 Arc 36 Arc 37 0 0 0 0 0 5 3,685 0,445 0,600 0,270 50 48,685 0,445 0,600 0,270 200 198,685 0,445 0,600 0,270

Whenever the functions for attribution were not defined these are automatically made equal for all the arcs that do not represent derivations.

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The functions for the attribution of water consumption can be different for each period of analysis during the year of simulation of the system, but they cannot be different from one year to the next. This is the case for consumption for irrigation purposes. Table 22 – Consumption for irrigation purposes in the CuneneB0 system

The consumption rates that were adopted for the simulation of system CuneneB0 are presented in Table 22.

Page 186/214 LNEC – Proc.605/1/11926 For those nodal points that represent dams, the data were introduced that define the relationship between the water quotas and the volume of the dam in question, and the operation conventions for each period of analysis during the year. These data include: - total volume and initial storage volume; - minimum outflow or discharges, if applicable, correlated to the storage volume; - functions level-based volume and level-based flooded area; - daily losses through evaporation (height or volume by area unit).

Tables 23 to 30 portray the values of the curves level-based volume and the area of the free surface that has been adopted for the simulation of the systems CuneneB1 to CuneneB5, respectively for Gove, Matala, Calueque, Ruacana, Jamba-ia-Oma, Jamba- ia-Mina, Catembulo and Cova do Leão.

The values that are depicted have been taken from publications (Gove and Matala), from projects (Jamba-ia-Oma and Jamba-ia-Mina) or have been projected with the help of cartographic maps in supplement of some values that were available.

Table 23 – Quotas, volumes and surface areas of the Gove Dam

Table 24 – Quotas, volumes and surface areas of the Matala Dam

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Table 25 – Levels, volumes and surface areas of the Calueque Dam

Table 26 – Levels, volumes and surface areas of the Ruacana Dam

Table 27 – Levels, volumes and surface areas of the Jamba-ia-Oma Dam

Table 28 – Levels, volumes and surface areas of the Jamba-ia-Mina Dam

Page 188/214 LNEC – Proc.605/1/11926 Table 29 – Levels, volumes and surface areas of the Catembulo Dam

Table 30 – Levels, volumes and surface areas of the Cova do Leão Dam

The rates of outflows from dams that are based on stored volumes require the definition of the number of zones and the boundaries of these volumes for each zone, for each period of analysis within the year. In this manner, the following elements were indicated, wherever necessary, for each zone of the dam: - initial maximum storage volume and the respective outflow; - final maximum storage volume and the respective outflow; - initial minimum storage volume and the respective outflow; - final minimum storage volume and the respective outflow.

The values that were adopted for the various simulations are indicated in Table 31. Table 31 – Definition of the zones within the dams

Page 189/214 LNEC – Proc.605/1/11926 The data for evaporation from the four existing dams are shown in Table 32.

Table 32 – Evaporation from the four dams (mm)

For the other dams the same rates were adopted, namely Jamba-ia-Oma = Gove, Jamba-ia-Mina and Catembula = Matala, and Cova do Leão = Calueque.

Files containing the respective flow volumes were created for those nodal points that include hydrometric stations, to be read during simulation. All discharge data that were associated to any site for which observations were made had to be included in one single dossier, to be read during the simulation process.

The various flow volume dossiers with the rates that were adopted for the various simulations can be found in Appendix 3.

The files contain the following: - the number and names of the stations with flow volume records; - the constants for conversion of flow volumes and the units of discharge and volume; - the year of commencement, the number of years of records and the number of periods of analysis in the year; - the number of replications, repetitions and sequences of flow volumes.

Page 190/214 LNEC – Proc.605/1/11926 8.2.3 Data for the arcs

As for the nodal points, the data for the arcs has specific requirements in accordance with the types [of arcs].

The only common requirement for all arcs is the label. Similar to the procedure for the nodes, if no name was specified, it was given by default.

Hydroelectric plants or pumping stations may be situated on any arc. The data that was necessary for these centers were the following: - capacity (power) of the center and nominal charge of the project; - minimum discharge for the production of electricity, for the nominal charge; - factor of the central (fraction of time in which the electricity is produced) for each period; - constants for the production of electricity to convert to produced energy; - functions level-based volume in each of the two nodes (may be a constant).

The constants for electricity production convert the daily flow volumes and the charges into electricity. These constants include the efficiency factors of the central and the input conduits. Whilst these efficiency factors change along with the charges, they are considered to be constants by IRAS.

The constants for electricity production can be obtained via the following equation: Power (kW) = 9,81 x flow volume (m3/s) x charge (m) x efficiency factor

The electricity produced for each calculation cycle results from: Electricity (kWh) = Power (kW) x hours

The values adopted for the various simulations are portrayed in Table 33.

Page 191/214 LNEC – Proc.605/1/11926 Table 33 – Data for the arcs with electricity production

8.3 Results of the simulations by IRAS

The simulation has generated an enormous quantity of data, including the stored volumes, consumption and losses, production of hydroelectric energy in many locations and for a large number of time periods.

Examination of all these results may take an excessive amount of time, even if one makes use of the capacity that is available from IRAS for the presentation of interactive diagrams of temporal series and tables. It is not necessary to examine all the results that were obtained, but it is important to know where and when the system falls short and to choose some data for these critical periods.

To select the option to visualize by means of color-coding allowed the easy identification of periods in which the performance of the system was not satisfactory. This information helped to focus attention on the search for flaws in the systems.

It was necessary to define the parameters associated with each noteworthy variable in order to visualize by means of color-coding. These two values divide the range of the possible values for each variable that was simulated into three zones: the lower, medium and upper zones. These zones of the values of the variables would take on different meanings, depending on the type of variable and its interest to the user.

The perimeters that were defined did not affect the simulation. They just divide the values of any given variable into three ranges or zones that correspond to what the user considers to be satisfactory, worthy of notification or indicating a defect in the

Page 192/214 LNEC – Proc.605/1/11926 projected conditions. Each of the zones has a color assigned to it. The satisfactory zone is represented by green, the warning zone by yellow, and the defect zone by red. There are six options that result from the combinations of colors and the categorization of same in relation to the upper, medium and lower zones.

For example, the volumes of a dam may be described for option 1, where green corresponds to the average zone, yellow to the higher zone and red to the lower zone. The variable flow volumes may be described in option 2 whereby the green corresponds to the upper zone, the yellow to the medium zone and the red to the lower. An option 3 may be used for the losses through evaporation, whereby the green corresponds to the lower zone, the yellow to the medium zone and the red to the upper zone.

Option 4 is symmetric to option 1, which means that green continues to be the medium zone, but the yellow corresponds to the lower zone and the red to the upper. Options 5 and 6 only use two colors, the green for the medium zone and red and yellow respectively for both the upper and lower zoned.

For example, the levels that divide these three zones in the case of water supply to people (option 2) would respectively correspond to 60% and 30% of the normal rate, Tables 34 and 35.

In a similar vein, for the supply of irrigation perimeters the zonal limits were defined as shown in Table 36.

Between many options to present some or all of the values of the variables that were simulated over a certain time and for any given nodal point or arc, or in spatial terms at any point in time, the configuration of four graphs with simple variables was selected, as can be seen in Figure 38.

Page 193/214 LNEC – Proc.605/1/11926 Table 34 – definition of the limits of consumption in the urban areas of system CuneneA

Table 35 – Consumption in urban areas for CuneneB0 and subsequent systems

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Figure 38 – Example of a series of graphs showing the simulation results

Page 195/214 LNEC – Proc.605/1/11926 The graphs on temporal series can contain simple or multiple variables within one and the same diagram. The spatial graphs have as their horizontal axis the sequence of the arcs or nodal points.

Table 36 – Boundaries of the zones in the four dams (m)

During the simulations a dynamic succession of images can be seen that show the variation in time of the values of the variables. Each image shows each nodal point or arc (or the respective geographic representation) with a green, yellow or red color.

This visualization is not reproducible in a report, as it can only be seen on a computer screen.

In addition to the graphs for the temporal and spatial series, the statistical information also can be presented on the computer screens with the [required] reliability and resilience, for all variables for which perimeters were defined.

Tables 37 and 38 show the values that were obtained in the various simulations. Table 37 – Reliability of water supply in the Cunene River Basin

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Figure 39 – Example of probability projection of the simulation results

Page 197/214 LNEC – Proc.605/1/11926 Table 38 – Resilience of the water supply in the Cunene River Basin

8.4 Analysis of the results of simulations by IRAS

8.4.1 Simulation of system – CuneneA

The simulations that were carried out with the system CuneneA had two main objectives: to test the capacity of the IRAS program and to verify the relative importance of the various actual consumption rates as compared to the availability of water from the Cunene River.

The first of the two objectives led to a rather high number of simulations for the determination of the input data and in order to understand the main characteristics of the results that could be obtained from the simulations. As already mentioned, these simulations use just two years of data on flow volumes, in order to facilitate the physical interpretation of the results that are obtained. In this first series of simulations any flawed data on the definition of the physical system were successively corrected.

A first verification looked at the difficulty to include all the centers of consumption, due to the limitations that were imposed by the program, which are of just 60 nodal points and 60 arcs. However, as it had also been ascertained that the majority of the extraction points corresponded to very small quantities of water when comparing them to available flow volumes, it was decided to move to the system that was labeled CuneneB0.

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8.4.2 Simulation of system – CuneneB0

In system CuneneB0 the number of points of consumption and hydrometric stations with monthly flow records was reduced, and the simulations of consumption for agricultural purposes was introduced, which are quite significant in terms of water consumption.

The non-consideration of the existing dams allowed the verification of the relative significance of agricultural consumption that has occurred for some decades. This system would also be the one that would closely correspond to the situation that existed when the data on flow volumes were recorded between 1963 and 1973.

The simulations that were carried out showed that, for the irrigation perimeters at Humbe and Matala there were no supply deficits during the years of simulation, but that the derivation towards Namibia had insufficient water for 3 out of 24 months.

This final result indicates the need for regularization, which was [then] projected for the Gove Dam.

8.4.3 Simulation of system – CuneneB1

System CuneneB1 continued to take only two irrigation perimeters into account, but with 12 months‟ water attribution.

The simulation of the regularization at the Gove Dam was made by various exploratory theoretical curves. It was for example noted that, for a regularization of 200hm3/month at Gove, there were no deficits in the supply to Namibia, as long as one just allowed for two irrigation perimeters, those at Matala and at Humbe. The same happened with a regularization of 100hm3/month at Gove.

As far as hydroelectric production was concerned, taking a regularization of 100hm3/month into account, averages of around 300GWh/year at Matala and 2700GWh/year at Ruacana were obtained. It should be noted, however, that the latter

Page 199/214 LNEC – Proc.605/1/11926 calculation should be treated with some reserve in view of the insufficiency of trustworthy data on the characteristics of the turbines at the Ruacana plant. Yet, for the purposes of relative comparison of the various scenarios the calculated rate is important, even if it should not correspond exactly to what is installed at that dam.

8.4.4 Simulation of system – CuneneB2

System CuneneB2 differs from the previous one by the fact that irrigation is only projected for four months per year, but was expanded to 7 irrigation perimeters, also with average provisions in relation to the possible extremes, depending on the crop selection. [Once] all irrigation perimeters had been introduced, the Gove Dam and the hydroelectric energy production at Matala and Ruacana were looked at.

Taking 7 irrigation perimeters into account with 12 months of water distribution per year, and for an average provision as compared to the extremes that were mentioned above, the results that were obtained were different.

In as far as the irrigation perimeters are concerned that are supplied directly from the Cunene River, it was noted that water distribution is possible, with no or only insignificant flaws, as would be the case of the perimeters of Mulondo, Humbe and Cafu. However, as far as those perimeters are concerned that depend on the tributaries Colui and Caculuvar, the situation is totally different. In these two cases the water that is naturally available does generally not correspond to half of the required volume.

It was also noted that, due to the deviation of water for all the irrigation perimeters, the supply of water to Namibia was compromised for some months during the year, to be more precise, 5 times in 24 periods.

As regards the production of electricity, there was no change recorded for Matala after the deviation of water for irrigation purposes, which was to be expected in view of the fact that this station is situated upstream from the irrigation perimeters, and a slight decrease for an average production of 2650GWh/year at Ruacana.

Page 200/214 LNEC – Proc.605/1/11926 8.4.5 Simulation of system – CuneneB3

The scheme of Jamba-ia-Oma was introduced for system CuneneB3, with electricity production and an imposed flow volume of 100hm3/month.

It was found that the scheme practically reacts like a trickle of water, as the dam remains full at all times, with the exception of the first month of calculation, in view of the fact that the period of analysis is the month.

As regards electricity production it was noted that the production at this new scheme is of around 300GWh/year, with the production at Matala increasing to 400GWh/year and that at Ruacana decreasing slightly to 2620GWh/year. It should be noted, however, that these changes at Matala and Ruacana could also result from different initial conditions that were imposed by the simulation process. One should not only attribute them to the variation[s] of the simulated system. As a matter of fact, the simulations that were carried out also had other intentions, as regards other characteristics of the system that one cannot summarize in just a few paragraphs.

As anticipated, there were no significant changes to the supply of water for irrigation purposes and to Namibia.

8.4.6 Simulation of system – CuneneB4

One more scheme - that of Jamba-ia-Mina - was introduced for system CuneneB4. In addition, other and different impositions were considered as regards the management of the dams. Thus an initial volume of 1000hm3 was considered for Gove with the imposition of a regularization at the same scheme of 130hm3/month. No additional regularization was planned for the schemes at Jamba-ia-Mina and Jamba-ia- Oma (zero attribution according to the terminology of the program).

The introduction of this scheme did not change the allowances for irrigation and for Namibia to a[ny] significant degree.

Page 201/214 LNEC – Proc.605/1/11926 As regards the electricity that was produced, and taking the conditions of exploitation of the system into account, the following electricity productions were taken into account: 311GWh/year at Matala, 455GWh/year at Jamba-ia-Oma, 1411GWh/year at Jamba-ia-Mina and 2760GWh/year at Ruacana. In this manner production at Ruacana is increased and less at Matala.

8.4.7 Simulation of system – CuneneB5

Two more schemes were introduced for system CuneneB5, Catembulo, on the Colui tributary, and Cova do Leão, on the Caculuvar tributary. The objective of these two schemes is to ensure more water to the irrigation perimeters of Colui and Tchipa, respectively.

In fact, the inclusion of the first of these perimeters increases the water security from 26 to 90% and from 37 to 79% for the second. It is evident that these percentages are only valid for the period that was simulated, i.e. two years.

As far as electricity production is concerned, that at Matala remained the same, and that at Ruacana turned out to be less, at a level of 2600GWh/year, which could have been expected as water had been extracted from the system, upstream from the confluence of the Colui River.

8.4.8 Simulation of system – CuneneC5

System CuneneC5 is identical to CuneneB5, except for the number of years of simulation. In this case a period of 10 hydrologic years were taken, from 1963/1964 to 1972/1973, corresponding to a reconstituted historic series with the exception of hydrometric stations Cova do Leão and Humpata, with incipient data. For the purposes of this simulation the flow volumes of these two stations were considered as 5 replications of the volumes of the 2 years that were used in the prior simulations.

It was found that, for most of the years, the discharge at Jamba-ia-Mina was higher to that at Ruacana, with respective averages of 4915hm3/year and 3705hm3/year. However, in more humid years this correlation was inverted, which means that the

Page 202/214 LNEC – Proc.605/1/11926 discharge at Ruacana exceeded the one at Jamba-ia-Mina, which occurred in 30% of the years.

In this system the electricity produced at Jamba-ia-Mina exceeds that produced at Ruacana, with respectively 2900GWh/year and 2500GWh/year.

It was also noted that the supply to Namibia was insufficient for at least one month in 80% of the years.

The analysis of the evolution of the volume at Gove Dam, the important regulator of the flow volumes of the Cunene River, leads to the conclusion that the option to impose an attribution of 130hm3/month is high, which is why another system was defined.

8.4.9 Simulation of system – CuneneD5

The difference between this system and the previous one is only the attribution to Gove Dam that was reduced to 80hm3/month.

Under these conditions, the average annual discharges at Jamba-ia-Mina and at Ruacana are reduced to respectively 4755hm3/year and 3544hm3/year. The effect of this adjustment is mainly felt as regards electricity production, that decreases to about half, and the electricity that is produced at Ruacana turns out to be more than that at Jamba- ia-Mina, with respectively 1400GWh/year and 1200GWh/year.

The deficit of supply to Namibia also undergoes a slight increase.

One may thus realize how sensitive the production of electricity is as regards the regimen of exploitation of the Gove Dam, and that the supply to the consumption centers is of lesser influence.

Page 203/214 LNEC – Proc.605/1/11926 8.5 Synthesis of the simulations by IRAS

The simulations that were carried out by IRAS had the main objective to evaluate the possibilities of the utilization of water resources of the Cunene River Basin, to look at the data that were available on these resources and at some of the many scenarios for the use of water that could be considered.

The methodology used to attain the main objectives was the following: 1) Defining the various scenarios if using just two years‟ records of flow volumes. This allows much quicker substantiation of the general characteristics of the behavior of the basin for various hypotheses as regards development and, as a consequence, as regards the utilization of water. Care was taken in choosing one year‟s sequence that was averagely dry followed by one year that was averagely humid. The systems were labeled CuneneA to CuneneB5. 2) Carrying out simulations with a historic series that covered a period of 10 years, in two systems that were labeled CuneneC5 and CuneneD5, and that were developed on the basis of step 1).

The number of simulations that would be of ultimate interest for the implementation of the Master Plan for the Integrated Utilization of the Water Resources of the Hydrographic Basin of the Cunene River can be extraordinary high. For this reason additional simulations have to be made with systems as defined by GABHIC, in order to introduce the preoccupations on the planning and management of this international basin.

If one looks at the results of steps 1) and 2), it is already possible to synthesize some essential aspects for the utilization of the water resources of the Cunene River Basin.

The results from the use of the IRAS program allow to easily obtain the reliabilities (green and yellow reliabilities) of the water supply at the main consumption centers, in accordance with the definitions that were made for this study. However, it should be noted that these definitions depend on boundaries that were arbitrarily

Page 204/214 LNEC – Proc.605/1/11926 imposed for each decisive factor. For the present study these limits correspond to the non-satisfaction of respectively 60% and 30% of the nominal consumptions.

In a similar vein, the results of the resilience tests (yellow and red) were obtained that indicate the capacity of recuperation of the system when interruptions occur in the supply.

The results of the various simulations are presented on Tables 37 and 38 with the reliabilities and resiliencies.

The analysis of Table 37 allows the conclusion that the supply of the population centers does not present any difficulties, but that the supply to agricultural perimeters is already dependent to a large degree on the conditions for exploitation of the dams.

The irrigation perimeters for Colui and Tchipa, depending on the water from tributaries, are those that are the most difficult to supply, considering the scenario of average agricultural expansion.

The supply to Namibia that is extracted downstream from all the other consumption centers could as a consequence be sensitive to consumption upstream. However, it was ascertained that this vulnerability is not very important.

At the same time threshold values for reliability are presented via some perimeters, but these might easily be increased through other premises for simulation, as is the case with the perimeter of Matala.

The resilience factors that were obtained through the simulations do not require any special comments.

Another way to analyze the options for irrigation would be via the percentage of water that can be used for this purpose, comparing it with that [percentage] corresponding to requirements. These values are portrayed in Table 39 and correspond to the simulations carried out for systems CuneneB4 and CuneneB5.

Page 205/214 LNEC – Proc.605/1/11926 Table 39 – Percentages of water supply and requirement in the Cunene River Basin

Even if these percentages do not yet correspond to a significant period, the following may be concluded:

1) There is not necessarily sufficient water for all irrigation perimeters. 2) In order to implement the irrigation perimeters at Colui and Tchipa it is necessary to build the dams [that are planned] for Catembulo and Cova do Leão, respectively. 3) In the case of the hypothesis of utilization with intense irrigation, supplies to Namibia might suffer reductions.

As far as the production of hydroelectric energy is concerned, it was confirmed that this is much more sensitive to the exploitation of the dams, than what has been noted for the water supply for irrigation purposes.

Finally, it may be stated that the construction of the dams at Jamba-ia-Oma and Jamba-ia-Mina are more important for purposes of electricity production than for water supply for irrigation. As a matter of fact, the regulating effect of these two dams is minor when compared to that of the Gove Dam.

Page 206/214 LNEC – Proc.605/1/11926 9. EPILOGUE

The Plan for the Integrated Utilization of the Water Resources of the Hydrographic Basin of the Cunene River needs to by dynamic in nature and adapted to the actual conditions of the Angolan society.

The work that was carried out by the Laboratório Nacional de Engenharia Civil (LNEC) has to be adapted to various difficulties that were encountered en route, some prominent [problems] being:

 Limitations as regards the collection of information  Alterations to what was previously projected  The quasi total lack of visits to the basin, with the subsequent conditioning in terms of validations “in loco” of the elements that were adopted.

These aspects are relatively important as the work on water resources gains in robustness when direct access to the fluvial system is available, which was not possible in this case.

It would also have been of great interest to have access to the Feasibility Study for the Epupa Scheme, an aspect that could however be taken up at a later stage if it is decided to revise and update the present Plan.

Under these circumstances, if such a revision and update is decided, its implementation will have to take the following key objectives into account:

1) As soon as possible, implement the installation of some hydrometric stations, in particular in sites close to the schemes that have been projected. 2) To continue to be involved in the negotiations with Namibia as regards the sharing of water. What was resolved on a political platform depends on the development of water schemes in the Cunene Basin. 3) The recuperation [rehabilitation] of existing structures needs to be implemented before [any] new structures are built. 4) The supply for agricultural purposes can be made independently from the provision for electricity production. As a matter of fact, a quasi independent analysis can be made of these two types of schemes. 5) Specific feasibility studies could be carried out for each scheme, taking as a starting point the analyses that were made in the framework of this work, and that would be supplemented by new applications of the IRAS program, in order for its overall influence to be substantiated.

At Lisbon, LNEC, July 2001

VERIFIED BY: COMPILED BY: (signature) (signature) Carlos Matias Ramo João Soromento Rocha Head of the Department of Hydraulics Researcher-Coordinator (text based on various publications)

Page 207/214 LNEC – Proc.605/1/11926

APPENDIX I

Accord between the Government of Portugal and the Government of the Republic of South Africa on the 1st Phase of the Supply of Water Resources from the Cunene Basin.

[The original English version of this document is to be procured from the relevant ministerial sources]

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APPENDIX 2

Documentary references

Page 209/214 LNEC – Proc.605/1/11926 PLAN FOR THE INTEGRATED UTILIZATION OF WATER RESOURCES FROM THE HYDROGRAPHIC BASIN OF THE CUNENE RIVER

Inventory of documents that exist at LNEC

1990

Page 210/214 LNEC – Proc.605/1/11926 [The page numbers mentioned here refer to those of the original document; only the headings of the various documents are provided at this stage. ]

CUNENE BASIN – SCHEMA FOR HYDRAULIC SUPPLY 1966/67 (Page 213) PROJECT FOR HYDROELECTRIC SUPPLY AT GOVE (P.A.H. GOVE) 1965/67 (Page 214) SCHEME FOR JAMBA-IA-MINA – COBA (Page 215) SCHEME FOR JAMBA-IA-OMA – COBA (Pages 216/7) TENDER PROCESS FOR THE LINK MATALA-JAMBA-TCHAMUTETE (Pages 217/8) MISCELLANEOUS DOCUMENTS (Page 218) CLIMATOLOGIC INFORMATION 1959/72 (Page 219) METEOROLOGIC INFORMATION 1968/75 (Page 220) METEOROLOGIC OBSERVATIONS 1957/67 (Page 221) PRECIPITATION AND DISCHARGE (Page 222) FLOW VOLUMES, LIMNIMETRIC HEIGHTS AND HYDROGRAPHIC BASINS (Page 223) REPORTS (Page 224) GENERAL TECHNICAL DOCUMENTATION (Page 225) MISCELLANEOUS DOCUMENTS (Page 225) MAPS OF THE CUNENE RIVER (Page 226) PROJECTS ON THE CUNENE RIVER (Page 226) PROGRAMS FOR RECONSTRUCTION (Page 226) PROPOSALS ON THE CUNENE RIVER (Page 227) MATALA SCHEME Ministry for Overseas Affairs. 1951 (Page 227) FINANCING AND TENDER ADMINISTRATION (Page 227) HYROLOGIC STUDIES (Page 228) REITERATIONS (Page 228) NOT RETURNED AND WITHOUT BOX (Page 229)

Page 211/214 LNEC – Proc.605/1/11926

APPENDIX 3

Flowfiles

Page 212/214 LNEC – Proc.605/1/11926 GLOSSARY (PORTUGUESE TEXT IN SCANNED TABLES)

Portuguese English (a) em 1970 incluia a actual província do Cunene (a) in 1970 includes the actual Cunene Province albufeira(s) dam(s) algodão cotton ano(s) year(s) anos de seco sentidos no Sul da bacia do Years of drought felt in the south of the Cunene Cunene, segundo MORAIS (1947) Basin, according to MORAIS (1947) arco arc área area / zone / surface Área da bacia hydrográfica area [surface] of the hydrographic basin arroz rice atribuição aos attribution to bacia total total of basin citrinos citrus constante de energia constant [factor] for electricity consumo consumption consumo difícil difficult consumption consumo normal normal consumption consumo restringido restricted consumption cota quota cota da turbina quota of the turbine cota inferior lower quota cota superior upper quota da bacia of the basin das províncias of the provinces densidade density diferença das médias difference from averages diferença dos desvios padrão differences from deviation patterns Efluência no nó 18 tributary to node 18 escoamento discharge escoamento annual annual discharge escoamento mensal monthly discharge estação hidrométrica hydrometric station factor de produção production factor Fiab[ilidade] amar[ela] yellow reliability Fiab[ilidade] verde green reliability fonte source grupos etários age groups hab[itantes]/km2 inhabitants/km2 junto à fronteira next to the border limite inferior lower limit / boundary limite superior upper limit / boundary máximo maximum mês month meses months meses do ano hydrológico months of the hydrologic year

Page 213/214 LNEC – Proc.605/1/11926 mínimo minimum municipios municipal areas nome name nome da estação hydrométrica number of the hydrometric station Nome da povoação name of the population [group; tribe] número da estação number of station número dos nós da estação no sistema do number of the nodes of the station within the programa IRAS system of the IRAS program Número no sistema do programa IRAS number within the system of the IRAS program perimetro de rega irrigation zone [perimeter] Pmed = média ponderada weighted average potência power / strength precipitação rainfall precipitação annual annual rainfall província province regressão entre os escoamentos anuals (mm) regression between the annual discharge rates Resil[iência] amar[ela]. yellow resilience Resil[iência] verm. red resilience sub-bacia sub-basin tempo time / weather / speed unidade unit valores values, rates valores em Cº values in Cº valores em mm values in mm variação da média annual da precipitação variation as compared to annual average rainfall volume da população size of population

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