Environmental flow assessment as a tool for achieving environmental objectives of African water policy, with examples from East Africa

Africa has set ambitious targets for development of water resources over the coming decades. <italic>Africa Water Vision 2025</italic> calls for a doubling of irrigated agriculture and a five-fold increase in water use for agriculture, industry, and hydropower. The ambitious development targets are framed in the context of integrated water resources management, which also seeks to simultaneously allocate sufficient water for environmental sustainability. Over the past two decades scientists have devised a number of practical and robust approaches to determine environmental water requirements in rivers and wetlands based on the objectives set in water planning. We review the most widely applied approaches to assess environmental flow requirements and consider their application in Africa through case studies in the transboundary Mara River basin of Kenya and Tanzania and the Great Ruaha River basin in Tanzania.