The Amatikulu-Nyoni Rivers, Kwazulu- Natal, South Africa
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River discharge dynamics, climate and land-use change: The Amatikulu-Nyoni Rivers, KwaZulu- Natal, South Africa By Renate van Heerden Submitted in partial fulfilment of the requirements for the degree MSc Geography Department of Geography, Geoinformatics and Meteorology In the Faculty of Natural and Agricultural Sciences University of Pretoria Pretoria November 2018 DECLARATION OF ORIGINALITY UNIVERSITY OF PRETORIA I, Renate van Heerden, declare that the thesis/dissertation, which I hereby submit for the degree MSc Geography at the University of Pretoria, is my own work and has not previously been submitted by me for a degree at this or any other tertiary institution. Full names: Renate van Heerden Student number: 10013548 Degree: MSc Geography Topic: River discharge dynamics, climate and land-use change: The Amatikulu-Nyoni Rivers, KwaZulu-Natal, South Africa Supervisor: P.D. Sumner Co-supervisor: M. Loubser SIGNATURE: ……...………………………….. DATE: …………………………………. i Abstract Fluvial discharge dynamics, climate variability and land-use change: The Nyoni and Amatikulu Rivers Land-use changes and climate variability are known to affect environmental processes, and fluvio-marine environments tend to be extremely sensitive to these impacts. Hydrological models have been introduced in numerous studies to explore the responses in catchment processes. Spatially distributed rainfall-runoff models provide a more holistic view of the hydrological behaviour under different environmental conditions. However, the use of hydrological models in South African studies which investigate the impacts of climate and land-use change on discharge are scarce, and only a limited number have investigated the impact of climate and land use on catchment processes. What is of more relevance and importance in real-world applications is the differentiation between the respective roles of climate and land use on specific catchments. This study implements Spatial Tools for River basin Environmental Analysis and Management (STREAM), a GIS-based water-balance model, to investigate the major causes in change of discharge volume in the Amatikulu and Nyoni catchments (KwaZulu-Natal, South Africa). River and coastal morphological changes have also been observed in the recent past. This study proposed that land-use changes and climate variability have the largest influence on the change in discharge volumes; however, the exact extent needs investigation. Climate and land-use data for the period 1964-2015 are used for the model simulations. It has been found that land-use changes have had no significant impact on the discharge for this period, while climate has had the larger effect. Climatic scenarios corresponding to projected climate change have been investigated, and have shown that a 5°C increase in temperature would have the largest influence on discharge compared to the observed changes in land use. Keywords: River systems, discharge, climate, land use, hydrological modelling ii Acknowledgements I would like to thank my family and friends for their continued help, advice, guidance, support and patience throughout the duration of my research. It has not always been easy and without their continued support, I would not have persevered and finished this research. A special mention of the following is needed: My supervisor, Dr. Paul Sumner, for his willingness to help me with my research. I appreciate the direction he has given me throughout the process of completing my thesis. He has contributed greatly to the development of this idea and has always been keen to go on a field visit. My co-supervisor, Michael Loubser, who always encouraged me, especially in the moments when I thought this research was too much for me, and for always answering my queries, however small. Barend van der Merwe and Ingrid Booysen, who have always been able to direct me towards where I can find the information necessary for this project. The South African Weather Services (SAWS), for the rainfall and temperature data for the respective stations that were used in this research. Also the National Geospatial Information (NGI) for providing the spatial information that I needed. Hans de Moel for supplying me with the STREAM Matlab script. The University of Pretoria, for awarding me a bursary for my Master’s Degree. And finally, my friends and family, without whose support I would not have been able to persevere in my studies. iii Table of Contents Abstract ............................................................................................................................. ii Acknowledgements ........................................................................................................... iii List of Figures ................................................................................................................... vi List of Tables .................................................................................................................... ix List of Abbreviations .......................................................................................................... x List of Equations ............................................................................................................... xi Chapter 1: Introduction ......................................................................................................1 1.1. Study background .........................................................................................1 1.2. Aims and objectives ......................................................................................7 Chapter 2: Literature Review .............................................................................................9 2.1. Environmental change ..................................................................................9 2.2. Landscape evolution ................................................................................... 11 2.3. Hydrological connections and water resources ........................................... 13 2.4. Climatic influences on water resources ....................................................... 14 2.5. Land-use change influences on water resources ........................................ 15 2.6. Previous hydrological study methods .......................................................... 16 2.7. Hydrological modelling studies ................................................................... 18 2.8. Similar studies in Africa and South Africa ................................................... 21 Chapter 3: Study Area ..................................................................................................... 25 3.1. Location ...................................................................................................... 26 3.2. Climate ....................................................................................................... 28 3.3. Catchment characteristics........................................................................... 30 3.4. Land-use .................................................................................................... 36 Chapter 4: Method ........................................................................................................... 39 4.1. Data collection ............................................................................................ 42 4.1.1. Digital Elevation Model (DEM) .................................................................... 43 4.1.2. Crop factor maps ........................................................................................ 43 4.1.3. Soil water holding capacity map.................................................................. 45 4.1.4. Climate matrices ......................................................................................... 46 4.1.5. HEAT parameter ......................................................................................... 47 4.1.5. Mask ........................................................................................................... 48 4.1.6. Calibration map .......................................................................................... 48 4.1.7. Discharge points ......................................................................................... 49 4.1.8. Model calibration ........................................................................................ 50 4.2. Model simulations ....................................................................................... 51 iv 4.2.1 Determine land use and land-use changes for the study period .................. 51 4.2.2 Determine annual climate variability for the study period ............................ 53 4.2.3 Relationship tests ....................................................................................... 53 4.3. Scenario tests ............................................................................................. 54 Chapter 5: Results ........................................................................................................... 57 5.1. Land-use and crop factor maps .................................................................. 57 5.2. Climate ....................................................................................................... 61 5.3. Model calibration ........................................................................................ 64 5.4. Model simulations ....................................................................................... 65 5.4.1. The relationship between