UNESCO-IHE INSTITUTE FOR WATER EDUCATION at the UNESCO-IHE Institute for Water Education, Delft, the

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  • Impact of Climate Change on Water Resources Availability

    in the Komati River Basin Using WEAP21 Model

    Azman Bin Mat Jusoh

    MSc Thesis WM 07.19 June 2007

    UNESCO-IHE INSTITUTE FOR WATER EDUCATION

  • Impact of Climate Change on Water Resources Availability

    in the Komati River Basin Using WEAP21 Model

    Master of Science Thesis by

    Azman Bin Mat Jusoh

    Supervisor

    S. Graas (UNESCO-IHE)

    Examination committee

    Prof. Dr. P. van der Zaag, Phd., MSc (UNESCO-IHE), Chairman

    S. Graas, MSc (UNESCO-IHE)

    H. C. Winsemius, MSc (TU Delft)

    This research is done for the partial fulfilment of requirements for the Master of Science degree at the UNESCO-IHE Institute for Water Education, Delft, the Netherlands

    Delft, The Netherlands June 2007

  • The findings, interpretations and conclusions expressed in this study do neither necessarily reflect the views of the UNESCO-IHE Institute for Water Education, nor of the individual

    members of the MSc committee, nor of their respective employers.

  • i

    ABSTRACT

    The subject of changing or fluctuating climate is one of the central issues facing of the

    atmospheric sciences community. The most profound effect of such climatic changes may be

    major alterations in regional hydrologic cycles and changes in regional water availability.

    Within a context of increasing water scarcity, climate change threatens to exacerbate the current

    supply-demand imbalance. In this study, the impact of climate change on water availability have

    been modelled and evaluated.

    Using the integrated hydrological/water management model, known as WEAP21, this study

    evaluates the impact of climate change and investigates the sensitivity of water resources to

    climate change in a part of the Komati river basin. In addition, this study assesses the

    applicability of WEAP21 model as a hydrological model for climate impact assessment. Using

    four different climate change scenarios, WEAP21 has been utilised to simulate future water

    available in the study area for further analysis.

    The model shows its capability in producing the streamflow discharge in the calibration and

    validation process. The performance criteria of R2, CE, PE and VE computed indicates that the

    model satisfactorily simulates the streamflow volume in the catchment during the period of 1972

    to 1982. In the sensitivity analysis, it was found that the parameter of LAI and Kc were the most

    sensitive parameter to the model output. Using an optimum data available, four different climate

    change scenarios being applied in the model for simulations. Such scenarios have been

    developed by using hypothetical approach; alteration to the historical precipitation and

    temperature data available.

    The study found that the Komati river basin is very sensitive to climate fluctuations, suggesting

    that slight changes in the “mean” climate could alter present hydrologic conditions and its water

    resources. Based on the results obtained, the study area tends to experience a water scarce

    problem in the period of 2011-2030. This is because with an increase in temperature alone, the

    study area will face about 10% reduction in water availability.

  • ii

    WEAP21 successfully achieved the aim of this study; to test its capability as a hydrological

    model for climate impact assessment and to assess the impact of climate change on water

    availability in the study area. Nevertheless, uncertainty cannot be avoided in this study since the

    utilisation of the modelling for making the future prediction . However, a key feature of the

    model is its ability to characterise the complete hydrologic cycle, which allows the planner to

    track mass balance changes in terms of both the magnitude and nature of the water balance.

    Key words: climate change, hydrological model, water availability, water balance, WEAP21

    model, Komati catchment

  • iii

    ACKNOWLEDGEMENTS

    First and foremost, I thank to Almighty God for giving me this opportunity, strength and

    guidance that make the conclusion of this study possible, although sometimes it seemed very

    difficult.

    This study would never have materialised without the support and contribution of many

    individuals to whom I have the pleasure of expressing my appreciation and gratitude.

    My sincere gratitude goes to my supervisor, Ms Susan Graas for her guidance, support and

    valuable contribution of ideas in all stages of this study. Her intellectual inspiration, advice and

    regular lengthy stimulating discussions have been invaluable and helped me to produce this

    thesis in its present shape.

    I am very grateful to Professor P. Van der Zaag for his support, and effort in making available

    the necessary data for this study. I am also grateful to his contact in South Africa, Mr. G. Jewitt

    (University of Kwazulu Natal) in the provision of valuable data for this study.

    I would like to express my warm thanks to Professor R. E Schulze (University of Kwazulu

    Natal, South Africa) for valuable contributions of information and input data for this study.

    I owe special thanks to the Government of Malaysia for providing the financial support during

    my stay in The Netherlands. Special thanks also to my employer, the Department of Irrigation

    and Drainage of Malaysia for providing me a study leave to enable me to pursue this MSc study.

    I would like to thanks to all Malaysian friends, classmates and all UNESCO-IHE participants

    and staff for helping me in many ways during my studies and stay in the Netherlands.

    Finally, my gratitude and thanks to my wife and daughters for their endurance and sacrifice, and

    to my mother, brothers and sisters in Malaysia for their moral support and encouragement.

  • iv

  • v

    TABLE OF CONTENTS

    ABSTRACT.................................................................................................................................... i

    ACKNOWLEDGEMENTS ........................................................................................................ iii

    List of Figures.............................................................................................................................. vii

    List of Tables ................................................................................................................................ ix

    List of Symbols ............................................................................................................................. xi

    1 INTRODUCTION................................................................................................................. 1 1.1 Background .................................................................................................................... 1 1.2 Problem Definition......................................................................................................... 2 1.3 Objectives of the study................................................................................................... 4 1.4 Limitation of the Study .................................................................................................. 4 1.5 Study Approach ............................................................................................................. 4 1.6 Structure of the Report................................................................................................... 5

    2 LITERATURE REVIEW .................................................................................................... 7 2.1 Climate Change.............................................................................................................. 7 2.2 Projected Climate Change.............................................................................................. 8 2.3 Climate Change Impact Analysis................................................................................. 10 2.4 Climate Change Impact on Hydrology and Water Resources ..................................... 10 2.5 Evaluating Regional Hydrologic and Water Resources Impacts of Climatic Changes.

    ............................................................................................................................. ..........12 2.6 Methodology to Evaluate Regional Hydrologic Impact .............................................. 13 2.7 Generating Climate Change Scenarios ........................................................................ 13

    2.7.1 GCM Based Scenarios ......................................................................................... 13 2.7.2 Analogue Scenarios ............................................................................................. 14 2.7.3 Hypothetical Scenarios ........................................................................................ 14

    2.8 Methods for Generating Climate Scenarios Adopted in the Study.............................. 14

    3 DESCRIPTION OF THE STUDY AREA........................................................................ 15 3.1 Physical Features of the Komati River Basin .............................................................. 15 3.2 Description of the Vygeboom Sub-catchment ............................................................. 15 3.3 Climate.................................................................