Impacts of land use/land cover changes on spatio-temporal variation of groundwater recharge: the case of Borkena sub-basin, Awash River, Ethiopia

Long-term temporal changes in land use and land cover (LULC) in the Awash basin have a substantial impact on groundwater resources through modifying the composition of water balance components. Therefore, in order to manage groundwater resources sustainably, an estimation of the spatial and temporal variation of annual recharge as a function of LULC was conducted in the Borkena sub-basin using a GIS-based WetSpass-M model. Meteorological and biophysical data in grid format and lookup tables were used to run the model. The automated digital filtering baseflow separation approach is used to independently compute recharge in order to calibrate and validate the model using streamflow data; consequently, its R2 and NSE for validation are 0.93 and 0.9, respectively. Using LULC maps from 1988 to 2019, the recharge was estimated to be 12.6% of the mean annual rainfall (1,279.2 mm) in 1988 and 10.7% of the mean annual rainfall (1,277.4 mm) in 2019. The study's findings are crucial for the sustainable management, planning, and utilization of groundwater resources.