WetSpass model and chloride mass balance based groundwater recharge estimation: the Case of Golina River Basin, northern Ethiopia

The Golina River Basin is one of the semi-arid basins located in the northern part of Ethiopia where government intervention of groundwater-based irrigation practices is implemented. The intervention has resulted in the drilling of several boreholes leading to doubts whether the groundwater abstraction is sustainable or not. Hence, the purpose of this study is to estimate groundwater recharge of the basin using the WetSpass model and Chloride mass balance methods and, therefore, evaluate the sustainability of the current groundwater abstraction rate. The WetSpass model-based groundwater recharge estimation was carried out through the preparation of grid-based and database format (dbf) input parameters. These parameters include soil, topography, slope and seasonal precipitation, temperature, wind speed, potential evapotranspiration, groundwater depth, and land use/cover maps. On the other hand, the chloride mass balance method-based groundwater recharge estimation was carried out through preparation of annual mean precipitation, and average chloride concentration in rainfall and groundwater. The results of the WetSpass model indicate that the annual actual evapotranspiration is 681 mm, runoff 140 mm, and groundwater recharge 82 mm. On the other hand, the chloride mass balance method resulted in an annual groundwater recharge of 101 mm. Based on the WetSpass model results, a total of 18.8 MCM of water, which is 25% of annual groundwater recharge, can be safely extracted from the Golina River Basin without creating significant harm to the environment and the aquifer system. Therefore, the current total groundwater abstraction of 10.2 MCM from the Golina River Basin is sustainable.