APPLICATION OF WATER EVALUATION AND ALLOCATION PLANNING (WEAP) MODEL TO ASSESS FUTURE WATER DEMANDS AND WATER BALANCE OF THE CALEDON RIVER BASIN by ABEBE SEYOUM AYELE A dissertation submitted in fulfilment of the requirements for the degree Master of Engineering in Civil Engineering in the Department of Civil Engineering of the Faculty of Engineering and Information Technology, of the Central University of Technology, Free State, South Africa Supervisor: Prof Y.E. Woyessa Co-supervisor: Dr D.C. Edossa June 2016 © Central University of Technology, Free State DECLARATION I, the undersigned, declare that the dissertation hereby submitted by me for the degree Magister Technologiae (Engineering: Civil) at the Central University of Technology, Free State, is my own independent work and has not been submitted by me to another University and/or Faculty in order to obtain a degree. I further cede copyright of this dissertation in favour of the Central University of Technology, Free State. ABEBE SEYOUM AYELE Signature: …………………………. Date: ............................................ Bloemfontein, South Africa i © Central University of Technology, Free State ACKNOWLEDGMENTS First of all, I would like to thank the Almighty God for giving me health and energy, and for helping me to complete this study. I would like to thank also my supervisor Prof Yali Woyessa and my co-supervisor Dr Desalegn Edossa for their advice and guidance throughout my study. I am grateful for the assistance of many staff members from the Water Supply and Hydrology Division of the Department of Water Affairs and Sanitation (DWA) in Bloemfontein and the local municipalities in the Free State. I am also grateful for the assistance of individuals and organisations from the Lesotho side including the Director of the Department of Water Affairs (DWALS) as well as the Department of Rural Water Supply (DRWS), the Water and Sewerage Company (WASCO), the Lesotho National Development Corporation (LNDC), the Ministry of Agriculture and Food Security (MoAFS) and the Bureau of Statistics (BoS) for their cooperation in providing important data. I would like to acknowledge also all my friends in Maseru (Lesotho) who have always supported me, encouraged me, prayed for me and kept me going. I say a big thank you! Finally, I am thankful to my wife, Frehiywot Getachew, and my children (Tsiyon Abebe, Selam Abebe and Mikias Abebe) for their support, love and comfort during stressing times, as a result of my workload and this study. ii © Central University of Technology, Free State ABSTRACT The Caledon catchment is one of the 19 catchments in South Africa and three catchments in Lesotho. It covers part of the south eastern Free State in South Africa and northern part of Lesotho. It is important to evaluate the water resources of the catchment to satisfy the projected water demands and in order to plan for the future and make wise decisions. The objective of this study was to apply the Water Evaluation and Planning System version 21 (WEAP21) as a Decision Support System (DSS) tool for the allocation and development of water resources in the Caledon catchment. The model was structured according to three scenarios with a current account (2014) and reference period (2015-2050) to predict their possible impacts on the water balance and allocation of the region due to varied water demands. The scenarios are as follows: scenario 1: increase in population growth rates; scenario 2: irrigation activities in Lesotho; and scenario 3: implementation of environmental flow requirement (EFR) on Caledon River at a site referred to as C6. The first two scenarios are consumptive scenarios whereas the third is a non-consumptive scenario. Scenario analysis answers “what if” questions for the future. Population growth has contributed to water scarcity problem in many parts of the world. In this context, scenario 1 deals with the impact of an increase in population growth on the water balance after 2020 by analysing the unmet demands that will be incurred over the reference period. Scenario 2 also analyses the unmet demands if irrigation activities in Lesotho are increased after 2020. Scenario 3 evaluates the impact of the implementation of an EFR site at C6 – which is situated downstream of all demand sites of the catchment – on upstream demands. Projected water demands and unmet demands were evaluated for four water use sectors, namely, domestic, industry, irrigation and livestock. The catchment comprised of 46 demand sites which were categorised into four use sectors: 20 domestic demand sites, 11 irrigation sites, 10 livestock sites and five industrial sites in both rural and urban areas. iii © Central University of Technology, Free State The modelling results show that high population growth increases the water shortage to all water use sectors in the catchment. Under a high population growth scenario, the unmet demand occurred between May and October. However, under reference, EFR and irrigation scenarios, the unmet demand occurred only from June to September. The annual unmet demand will increase substantially after 2020 in a high population growth scenario and when the population growth rates are altered. The demand from the irrigation sector is covered or no unmet demands are registered in all years. This is because active irrigation activities happen from December to May when enough water is available from the rivers. The years 2025 and 2050 were chosen to evaluate the water balance situations in terms of supply and demand in the middle and at the end of the reference period under two water use scenarios (high population growth and irrigation added). The result shows that the river flows meet the projected demand in 2025. However, most rivers, including the main river (Caledon River), will not be able to meet the required demands in 2050. iv © Central University of Technology, Free State TABLE OF CONTENTS DECLARATION ............................................................................................................... i ACKNOWLEDGMENTS ................................................................................................. ii ABSTRACT ................................................................................................................... iii LIST OF FIGURES........................................................................................................ xii LIST OF TABLES ........................................................................................................ xiv LIST OF ACRONYMS AND ABBREVIATIONS .......................................................... xvi NOMENCLATURE ...................................................................................................... xvii CHAPTER 1: INTRODUCTION ...................................................................................... 1 1.1 Background ......................................................................................................................................... 1 1.2 Problem Statement ............................................................................................................................. 2 1.3 Objectives ........................................................................................................................................... 4 1.4 Structure of Dissertation .................................................................................................................... 4 CHAPTER 2: LITERATURE REVIEW ............................................................................ 5 2.1 Introduction ........................................................................................................................................ 5 2.2 Water policies and water laws ........................................................................................................... 6 2.3 Water Allocation Guidelines and Principles ....................................................................................... 7 2.4 Water Resources Management Models for River Basin Simulation .................................................. 8 2.4.1 MODSIM ................................................................................................................................ 9 2.4.2 MIKE BASIN ........................................................................................................................... 9 2.4.3. RIBASIM ............................................................................................................................... 10 2.4.4. REALM ................................................................................................................................. 11 2.4.5. WEAP21 ............................................................................................................................... 12 CHAPTER 3: MATERIALS AND METHODS ............................................................... 16 3.1 Introduction ...................................................................................................................................... 16 viii © Central University of Technology, Free State 3.2 Description of the Study Area ........................................................................................................... 16 3.2.1 Geography ........................................................................................................................... 16 3.2.2 Climate ...............................................................................................................................