Groundwater Recharge Assessment Using WetSpass and MODFLOW Coupling: The Case of Hormat-Golina Sub-basin, Northern Ethiopia

Abstract

Water scarcity in northern Ethiopia, as well as its socio-economic relevance in terms of water demand for agriculture and domestic use, are at the root of the search for new groundwater resources and the development of groundwater models that can be used to control and manage the resource. The groundwater recharge of the Hormat-Golina sub basin was assessed using WetSpass-MODFLOW coupling. The goal of this paper is to assess the groundwater recharge in the Hormat-Golina sub-basin. These findings are then used to simulate the hydraulic head distribution using the MODFLOW groundwater flow simulation model. By comparing measured and simulated hydraulic heads, the steady state groundwater flow calibration was obtained. WetSpass calculated the mean annual evapotranspiration, surface runoff, and groundwater recharge to be 516.6, 204.9, and 35.6 mm, respectively. Groundwater recharge accounted for 4.7% of precipitation, while actual evapotranspiration and surface runoff accounted for 27% and 68% of precipitation, respectively. In such seasonal variations, the groundwater head distribution is 9.37 to 29.86 m in the winter (dry season), 9.53 to 29.89 m in the summer (wet season), and 9.58 to 30.17 m in the annual stress periods (recharges). For all stress periods, the estimated hydraulic heads in steady state fit well with the measured ones, with a correlation coefficient of 0.86 (summer, winter, and annual recharge). To preserve the resource's long-term viability, the balance between groundwater recharge and projected abstraction rates for agriculture and domestic water supply must be considered in future groundwater resource development plans in the valley.