INVITED SPEAKER

Climate change impacts on water supply and demand for selected urban and irrigation water supply systems in southern Africa

Prof. Dominic Mazvimavi
University of Western Cape, South Africa

Abstract

Climate change projections indicate that most parts of southern Africa will experience a decrease in rainfall although models differ in the predicted magnitude of the change. Most water supply systems serving large urban areas and irrigation utilize water stored in large reservoirs. The predicted changes in rainfall and evaporation will affect the reliability with which current and future water supply systems will be able to meet the water demand. The expansion of water storage is a possible adaptation to climate change effects on water supply.
This paper investigates how the water supply to urban areas in Botswana and Windhoek in Namibia are likely to be affected by climate change. The paper also investigates climate change effects on water supply for sugar cane production on 25,000 hectares in Zimbabwe. Major urban areas in Botswana such as Gaborone, Francitown, Lobatse and other major villages are located in a semi-arid region receiving on average 400 – 550 mm/year of rainfall. These urban areas are supplied with water from several dams with a combined capacity of about 344 Mm³ and linked by a 361 km pipeline called the North-South Water Carrier. Windhoek, the capital city of Namibia is also located in a semi-arid region receiving on average 360 mm/year of rainfall and depends on 3 dams with a total capacity of 155 Mm³ plus groundwater and water recycling. Sugar cane production in the south-east of Zimbabwe depends on water supply from 5 dams with combined capacity of 1,898 Mm³. All the 3 case studies examined are in semi-arid regions with low runoff coefficients and highly vulnerable to climate change induced changes on runoff.
Regional downscaled climate change projections for several climate models are used to determine the possible changes in rainfall and runoff. Use of several climate models is done to determine the sensitivity of each water supply system to climate change. Reservoir simulations using adjusted inflows, current and projected demand is carried out to assess climate change effects on meeting the water demand. The paper then examines the cost implications of expanding the water infrastructure as an adaptation to climate change.

Biography of the Invited Speaker

Dominic Mazvimavi is the Professor of Water and Environmental Science in the Department of Earth Sciences, and Director of the Institute for Water Studies which are both at the University of the Western Cape in Cape Town, South Africa. Prof Mazvimavi obtained a PhD in Hydrology from the Wageningen University and the International Institute of Geo-information Science and Earth Observation in the Netherlands. From 2007 to 2010 he served as the Managing Guest Editor for an annual special issue of the Journal of the Physics and Chemistry of the Earth covering papers on water resources management. Prof Mazvimavi has research interests on water resources planning and management, hydrological regionalization, effects of land-use change on runoff, and environmental flow assessment. He has previously worked at the Okavango Research Institute of the University of Botswana, and Department of Geography and Environmental Science of the University of Zimbabwe.