Climate and land use change impacts on base flow and groundwater recharge in the Ngono river catchment, Tanzania

ABSTRACT The Kagera River Sub-Basin is a transboundary water system in East Africa supporting water supply, agriculture, hydropower, ecosystems, and livelihoods. . This study evaluates the impacts of climate change and land use/land cover (LULC) change on baseflow and groundwater recharge in the Ngono River catchment using the Soil and Water Assessment Tool (SWAT). Historical data established baseline conditions, while future climate projections for 2041–2060 under three Shared Socioeconomic Pathways (SSP1–2.6, SSP2–4.5, SSP5–8.5) and projected 2050 LULC were used for future simulations. The model was calibrated and validated using the SUFI-2 achieving R2 values of0.74 and 0.72 and Nash–Sutcliffe efficiency (NSE) values of 0.71 and 0.68, respectively . Separate climate-only, land use–only, and combined scenarios were evaluated. LULC change alone resulted in less than 2% variation in baseflow and groundwater recharge.. In contrast, climate change reduced baseflow by approximately 74–75% ( 102.03 to 25.50–26.76 mm/y) and increased groundwater recharge by 11–13% (931.16 to 1,032.85–1,048.32 mm/y). The findings indicate that climate has a greater influence on catchment hydrology than LULC change, emphasizing the importance of climate-informed water resources management and adaptation .