Despite the apparently desperate situation of sub-Saharan Africa, rainwater harvesting and management is a viable intervention for upgrading rain-fed agriculture, improving water supply and sustainable livelihoods in water-scarce river basins. If strategies are developed to ensure equity allocation of basin water, a win-win situation for diverse water users can be achieved. This thesis assesses the hydrological impacts of land use changes on water resources management and socio-economic development of the upper Ewaso Ng’iro river basin in Kenya. It considers the impact of irrigation on dry season river flows and highlights the challenge of flood storage strategies. While flood storage can reduce dry season irrigation water abstractions by more than a half, without affecting hydro-ecological functions downstream, unplanned flood harvesting may impact negatively on flood flow, being detrimental to natural ecosystems and groundwater downstream.