Water productivity in Africa is the lowest in the world, and is further stressed by a rapidly growing population and the challenges posed by climate change. Africa contains about nine percent of global freshwater, and is characterised by large disparities in rainfall distribution and water availability across the continent (Joto Africa, 2009). Considering that Africa currently hosts almost 15% of the world’s population which is projected to increase to 17.5% by 2025 (UN, 2008), it is clear that relative water scarcity is on the increase. Africa is moreover the only continent where growth of food production has not kept pace with population growth in recent decades; yet performance of the agricultural sector is crucial for long-term growth prospects (UNECA, AU and AfDB, 2000), not least because 80% of Africans rely on agriculture for their livelihoods (Alliance for a Green Revolution in Africa, 2009).
The vast majority of African farmers rely on rainfall for food production: 95% of agricultural production in Africa comes from rainfed areas (UNEP, 2009). Productivity levels are low and grain yields oscillate typically around 1 ton per hectare. There is an important yield gap between experimental results and farmers’ reality (Rockström et al., in press). The key to closing the gap lies in improved water management. African countries on average only store 4% of annual flow (WWDR3, 2009), and a low water buffer means high vulnerability to both droughts and floods. Risk of climatic anomalies in Africa will even increase as a result of climate change (Conway, 2009). By 2020, 75-250 million people may be exposed to increased water stress due to the combined effects of climate change and increased demand(IPCC, 2008).