Impact of Climate Change on Water Resources in Eastern Africa

Impact of Climate Change on Water Resources in Eastern Africa

Alfred Opere (University of Nairobi, Kenya), Anne Omwoyo (University of Nairobi, Kenya), Purity Mueni (University of Nairobi, Kenya) and Mark Arango (University of Nairobi, Kenya)
DOI: 10.4018/978-1-7998-0163-4.ch010

Abstract

Climate change is causing great impact on water resources in Eastern Africa, and there is need to establish and implement effective adaptation and mitigation measures. According to IPCC, less rainfall during the months that are already dry could increase drought as well as precipitation, and this has great impact on both permanent and seasonal water resources. Increased sea surface temperature as a result of climate change could lead to increased drought cases in Eastern African and entire equatorial region. Climate change will also result in annual flow reduction in various river resources available within the region such as the Nile River. IPCC predicts that rainfall will decrease in the already arid areas of the Horn of Africa and that drought and desertification will become more widespread, and as a result, there will be an increased scarcity of freshwater even as groundwater aquifers are being mined. Wetland areas are also being used to obtain water for humans and livestock and as additional cultivation and grazing land. This chapter reviews the climate change impacts on water resources within the Eastern Africa Region. The climate change impacts on different water resources such as Ewao Ngiro have been highlighted and projection of future climate change on water resources examined. Stream flow for Ewaso Ngiro was found to have a significant increasing trend in 2030s of RCP4.5 and non-significant decreasing trend in stream flow in 2060s for RCP4.5.
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Indices Of Water Resources Stress

There are many possible indices of water stress, considering different aspects of use and availability. The basic measure used in the Comprehensive Assessment is the ratio of the amount of withdrawals to the renewable resources available in a country, including runoff imported from upstream regions. In the absence of consistent data at more local scales, the indices are calculated using national population and water resource statistics. Baseline estimates of national water resources, both generated internally and imported from upstream, are taken from data prepared for the Comprehensive Assessment, as are figures for current withdrawals. Future withdrawals of water will increase with population. It is assumed that the per capita use will remain constant over the next few decades although this is perhaps unrealistic, because in practice, use would change as economic development changes, water use efficiency increases and irrigation use increases at different rates compared to population. Climate change might also have an effect on the demand for water.

It is generally accepted that water resources become a constraint on development when use exceeds 20% of the total resources potentially available (Falkenmark 1989). In countries prone to severe problems during drought years in absence of secure supplies through investment in supply facilities, development opportunities are constrained. Countries using less than 20% of total potential resources are not immune to water stress and may experience severe problems in some regions and at some times.

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