A modeling approach for evaluating and predicting the impacts of land use land cover changes on groundwater recharge in Walga Watershed, Upper Omo Basin, Central Ethiopia

Study region: Walga watershed, Upper Omo basin, Ethiopia (2349 km2). Study focus: This research aimed to understand and predict the impacts of LULC changes on groundwater recharge in Walga watershed. Thus, the historical LULC changes in Walga watershed was assessed from Landsat: 4-5 TM, 7 ETM + and 8 OLI-TIRS (1990, 2006, and 2021), through Hybrid classification of unsupervised and supervised scheme using Erdas Image 2015, while future LULC was predicted using CA-Markov chain analysis approach in QGIS-MOLUSCE plugin. The LULC change impact scenarios on groundwater recharge was assessed using SWAT model. New hydrological insights: The evaluation of LULC changes pointed out that Walga watershed has undergone high intensity of LULC changes (1990-2021) due to anthropogenic activities and predicted to instantly change in the coming (2021-2035). The hydrological assessments indicate that groundwater recharge was declined over the last three decades by 20.84 mm and predicted to decline in future (2021-2035) by 6.17 mm. This implies that the declined recharge was linked to LULC changes over time with deforestation and agricultural land expansion. This means due to changes in agriculture (+26.3 %, +15.4 %), mixed forest (-3.7, -2.3 %), rangelands (-23.8 %, -8.8 %), grazing land (-2.6 %, -2.0 %), and urban (+1.14 %, +0.46 %) during (1990-2021) and (2021-2035). These outcomes provide baseline information for decision makers concerning LULC and groundwater for better planning and management strategies in the watershed.