In arid regions in Africa – where water is a limited resource – the impacts of climate change and water resources development are of particular concern, especially in international river basins. One example is the Zambezi basin that is shared by eight countries in the southern part of the African continent.
Recent institutional strengthening with the establishment of the Zambezi Watercourse Commission (ZAMCOM, which came into force in 2011) aims at efficient and sustainable water resources management in the basin. In contrast learn more to the Nile basin – where water resources are heavily exploited – irrigation projects in the basin are currently of limited importance, but large extensions are planned for the future. Two of the world’s largest hydropower reservoirs (Kariba, Cahora Bassa) were already built in the middle of the 20th century at the Zambezi River, providing electricity for the region, but with significant downstream effects on river ecology. The historic impacts of Kariba and Cahora Bassa dams on Zambezi discharge were analysed by Beilfuss and dos Santos (2001) Alisertib and Matos et al. (2010) and there have been several studies proposing optimized operation rules to balance energy generation and ecological downstream impacts (e.g. Gandolfi and Salewicz,
1991, Tilmant et al., 2010, Beilfuss, 2010 and Mertens et al., 2013). There is concern that future development of large-scale irrigation projects may significantly reduce Zambezi River discharge, with negative impacts on hydropower and ecology
(Hoekstra, 2003 and World Bank, 2010). On top of this, Zambezi discharge is also susceptible to possible future changes in climate (for a general overview see Beilfuss, 2012). There are a few modelling studies that analysed future runoff conditions in the Zambezi basin under scenarios of climate change and water demand. This approach requires a fully-fledged hydrological modelling of the water fluxes in the basin and is therefore a considerable task, especially due to the fact that the models are set-up in a large, data-sparse region with a unique hydrology. Harrison and Whittington (2002) studied future energy generation crotamiton at the proposed Batoka Gorge hydro-power plant at the Zambezi River below Victoria Falls. They modelled significant reductions in future discharge, albeit cautioning that “there is concern regarding the ability of the hydrological model to reproduce the historic flow”. Yamba et al. (2011) applied the Pitman water balance model with selected climate scenarios to the full Zambezi basin to assess future energy generation at large hydro-power plants, obtaining results that show gradual reductions in discharge owing to climate change and increasing water demand.