Scenario-based analysis of upstream land use Land Cover Changes (LULC) in the Densu River Basin (DRB) on catchment hydrology including the Weija Reservoir, Ghana

Study region: Densu River Basin (DRB) in Ghana. Study focus: Urbanization, agricultural expansion, and population growth are transforming land use across West Africa, impacting hydrological regimes and ecosystem resilience. This study assesses land use and land cover (LULC) changes in Ghana’s Densu River Basin (DRB) using the Soil and Water Assessment Tool (SWAT). The model, calibrated (2012–2019) and validated (1990–2011) with streamflow data, showed strong performance (NSE = 0.79; R² = 0.85). Three LULC scenarios – agriculture-, forest-, and urban-dominated – were simulated using satellite imagery from 1990 to 2019. The 2018 Landsat baseline map, validated with 91.5% accuracy, showed the urban scenario increased surface runoff (>50% of water yield) and sediment load (>83,000 metric tons/year), while the forest scenario enhanced percolation and groundwater recharge. Sedimentation in the Weija Reservoir, a key water source for Greater Accra, deposits ∼47,500 m³ annually, posing long-term risks to reservoir capacity and water security. These findings highlight tropical catchment's vulnerability to land use changes and support scenario-based hydrological modelling for river basin planning in rapidly urbanizing, data-scarce sub-Saharan Africa.