Abstract:
Estimating and mapping groundwater recharge is crucial for sustainable and well-planned groundwater resource management. The Gumara watershed (1266 km²), in Northern Ethiopia, encompasses both rural and urban areas that primarily rely on groundwater for domestic and related purposes. However, there are significant spatial and temporal variations in groundwater availability, leading to insufficient supply when and where it is needed. This study was aimed to estimate groundwater recharge and identify potential groundwater zones within the Gumara watershed. Utilizing WetSpass hydrological GIS-based model, which balances water, the study incorporated hydro-meteorological and physical data to simulate temporal averages and spatial distributions of surface runoff, actual evapotranspiration, and groundwater recharge. Using the average annual rainfall of 1462.2 mm as a starting source, the model results 18.3% of the rainfall contributes to groundwater recharge, while 41.3% is lost to evapotranspiration, and 40.4% to runoff. Notably, 95% of the recharge occurs during the wet season. The calibration and validation of the model were performed using R² (0.92 and 0.90) and NSE (0.80 and 0.79), respectively. The study was done for the periods 1990-2010 for calibration and 2011-2020 for validation. For the GWP map of the Gumara watershed, approximately 62.9% of the area was classified as having medium potential, 25.9% as high, and 11.2% as very high groundwater potentials. The map was validated using existing sources, which were mostly found in the medium potential zones. Given that the simulated recharge was significantly lower than the water lost through evapotranspiration and runoff, implementing artificial groundwater recharge methods could enhance water resource availability. Recommended methods include constructing farm ponds, bunds, and check dams to facilitate artificial recharge. Using both ArcGIS and MCDA in coordination is important to prove effective for monitoring and evaluating groundwater resource potential sites to ensure their proper utilization.
Key Words: Ground water recharge, Artificial recharge, wetSpass model, GIS,Gumara watersh