Assessment of groundwater recharge variability in the Usangu Plains under projected climate scenarios (2021–2050) for RCP 4.5 and RCP 8.5

In the Usangu Plains of Tanzania, groundwater plays a crucial role in maintaining surface water as well as meeting domestic and agricultural water needs. This study aims to evaluate the influence of future climate projections on the water budget components, namely surface runoff, actual evapotranspiration (AET), and groundwater recharge, using the WetSpass model. Groundwater recharge varied from −205.66 to 7.6E-06 mm during the dry season, 0 to 2973.96 mm during the wet season, and 0 to 2,968.91 mm annually under RCP 4.5. Under RCP 8.5, recharge ranged from −205.66 to 6.25 mm in dry periods, 0 to 2,985.18 mm in wet periods, and 0 to 2,988.49 mm annually. Groundwater recharge is expected to be low in the central region, high in the southern and some southwestern regions, and moderate elsewhere. Results indicate SR and AET, while recharge declines in magnitude and spatial distribution. The decline in recharge will affect surface water within the area due to its hydrological interconnections, leading to reduced water availability for agricultural, domestic, and economic needs. Therefore, proactive engagement from water users and stakeholders is essential for ensuring sustainable water resource planning and management. Strategies to minimize surface runoff and AET are recommended to enhance both focused and diffuse recharge across the Usangu Plains.