The Significance of Small Reservoirs in Sustaining Agricultural Landscapes in Dry Areas of West Africa: A Review

Abstract

Water scarcity is a growing challenge in semi-arid and sub-humid areas. There are over 2000 small reservoirs (SRs) with storage capacities of up to 1 × 106 m3 across West Africa’s dry areas. Based on a comprehensive literature review, we found strong evidence that SRs enable improved food security, livelihoods, and income diversification through fishing and livestock production. However, their productivity is far below their potential. Evidence on water quantity and quality is scattered, making deriving conclusions difficult. Review findings suggest that, unlike large dams, SRs have minimal impact on water balance and rainfall-runoff. There is, therefore, considerable potential to develop more SRs. However, high rates of sedimentation substantially reduce reservoir storage capacity. Poor irrigation management and agronomic practices also contribute to low productivity. Water quality is not systematically monitored, so SRs can increase health risks such as malaria and schistosomiasis. With the intensification of settlements, livestock, and agriculture around the reservoirs, it is critical to improve water quality and quantity monitoring. We conclude that SRs are important nature-based solutions, but need more investment to support the climate-proofing of agriculture and livelihoods. We recommend governments develop long-term small reservoir support programs to strengthen local capacities to manage the reservoirs and their watersheds sustainably.