Grid-scale groundwater recharge modeling and the spatiotemporal variability under climate change on Gidabo catchment in Ethiopia

Groundwater is a vital natural resource that supplies water for agricultural, industrial, and domestic sectors. Globally, groundwater has typically been quantified at coarse scales, which are unsuitable for finer-scale decision-making. This study was quantified groundwater recharge from Gidabo catchment in southern Ethiopia at a finer grid scale (0.1° ~11*11 km²). The approach utilized gridded model (HBV: Hydrologiska Byråns Vattenbalansavdelning), with input gridded data of parameters, precipitation, and potential evapotranspiration, to simulate recharge within its groundwater module. Additionally, the influence of future climate change on groundwater recharge was analyzed using Regional Climate Models (RCMs) under the RCP8.5 scenario after regridding them to 0.1°. Further analysis was done to quantify the variations in annual and seasonal groundwater recharge induced by climate change. The findings showed sufficient performance of gridded parameters and forcing datasets in reproducing the observed streamflow. The performance was revealed by median KGE during calibration (0.55), and validation (0.77) at monthly scale. The spatial average of groundwater recharge within the catchment has resulted to be 324 mm/year in the historical periods, however, climate change has altered this value to 264 mm/year, 234 mm/year, and 231 mm/year in the near-future, mid-future, and far-future periods, respectively. On grid scale future-period annual groundwater recharge was significantly reduced from historical values, particularly in grid cells in the north, reaching a maximum decline of 68% in the mid-future. In contrast, the center and south of the Gidabo catchment resulted in increased groundwater recharge for the near-future and mid-future periods. Seasonally, the historical maximum wet-season recharge value of 449 mm/5months has increased to 628 mm/5months in the near-future. Conversely, dry-season recharge in each grid has declined substantially across all future periods. This study supports the optimized utilization of groundwater in space and time under the influence of climate change.