Simulating Climate Impacts on Water Resources: Experience from the Okavango River, Southern Africa
The Okavango River is one of the largest and most important rivers in Southern Africa. The river rises in Angola, a country that has just emerged from a civil war of three decades. The annual flood pulse of the river feeds the Okavango Delta: one of the m
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Abstract The Okavango River is one of the largest and most important rivers in Southern Africa. The river rises in Angola, a country that has just emerged from a civil war of three decades. The annual flood pulse of the river feeds the Okavango Delta: one of the most valuable environmental resources of the African continent. The Okavango River water and its ecosystem resources are critically important sources of livelihoods in the basin. Pressures from livelihoods and development are already impacting on the environment and are likely to increase. Moreover, future development will occur against the background of climate variability and change. This chapter describes research conducted under the EU-funded project‘Water and Ecosystem Resources in Regional Development’ (WERRD), whose aims included development of scenario modelling as a tool for integrated water resource management in the Okavango River basin. The impact of climate change scenarios on downstream river flow and flooding in the Okavango Delta are simulated using a suite of hydrological models. The simulated impacts of climate change are sensitive to the choice of GCM and the IPCC SRES greenhouse gas (GHG) emission scenarios. The simulated impacts are considerable larger that those of the selected development scenarios although the uncertainty in the magnitude of future changes remains high. Keywords Climate change · Impacts · Hydrology · Hydrological model · Water resources · Adaptation · Uncertainty · Okavango · Scenarios
M.C. Todd Department of Geography, University College of London, 26 Bedford Way, London WC1H 0AP, UK, Tel. +44 20 7679 4271, Fax +44 20 7679 4293 e-mail: [email protected]
S. Sorooshian et al. (eds.), Hydrological Modelling and the Water Cycle, 243–265 C Springer Science+Business Media B.V. 2009
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1 Introduction The Okavango river is one of the largest river systems in Africa. The river system can be considered to consist of (i) the large basin area (approximately 165000 km2 ) which spans three riparian states of Angola, Namibia and Botswana (ii) the distal part which is a large inland alluvial fan known as the Okavango Delta in Botswana (Fig. 1). Streamflow is mainly generated in the upland regions of central-southern Angola (82% of the basin area lies in Angola) where the Cuito and Cubango rivers rise. These rivers merge in the extreme southeast of Angola and cross the Namibia/Angola border, before flowing into the Okavango delta. The Okavango delta is maintained by annual flooding of the Okavango River creating the world’s second largest inland wetland region: a unique, dynamic mosaic of habitats with exceptionally high beta diversity. The inundated area varies in area from about 5000 km2 to 6000–12000 km2 , depending on the size of the annual flood. It is one of the WWF’s top 200 eco-regions of global significance and the world’s largest Ramsar site. As a whole, the Okavango is the last near pristine river system in Africa. An overview of the mean climate of the region is provided in Section 5.3.
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