Assessment of surface water availability under different development and management scenarios in Kagera Basin, Tanzania

The Kagera basin faces increasing pressure to meet water demand for competing uses, necessitating a close look at social, economic, and environmental impacts of development. Recent years have seen significant growth in hydropower (Rusumo 80 MW, Kikagati 14 MW, Kakono 87 MW) and irrigated agriculture. Additionally, the full irrigation potential is planned for expansion from 45.15% (2016), alongside 94.71 ha allocated for large-scale manufacturing across six sub-catchments. To assess the impact of these developments on water availability, three scenarios (recent, medium-term, and long-term) were simulated using the MIKE HYDRO Basin model. This model, calibrated with baseline data (1982–2012), used river gauge data and the NAM rainfall-runoff model to estimate discharge and input flows. Results project total water demand to nearly double by 2040, reaching 823.4 Mm³/year, up from 415.2 Mm³/year in 2016. Water deficits are most severe from July to September, with the Kagera catchment showing the highest shortages, reaching 80.1 Mm³/year by 2040. Multi-Criteria Analysis (MCA) indicates Scenario 2 (irrigation capped at 60%) as the most sustainable, balancing social, economic, and environmental needs. These findings call for a re-evaluation of Kagera Basin development plans to align with sustainable water resource management.