Application of a spatially distributed water balance model for assessing surface and groundwater resources: a case study of Adigrat area, Northern Ethiopia

Abstract

The study area is located in the northern part of Ethiopia and covers an area of 279km2. The study area is one of the most water-stressed areas of Ethiopia, which is characterized by erratic nature with short period of rainy season that lasts from late June to early September. As a result surface water is limited, making groundwater the main source of water for domestic and irrigation purposes. Hence, the main objective of this research work is to assess the available water resource of the study area using a GIS-based distributed water balance model (WetSpass). This model depends on the spatial variations of land use, soil texture, topography, slope, groundwater level, and hydro-meteorological conditions. Input data for the WetSpass model were prepared in the form of grid maps and parameter attribute tables. The parameter attribute tables were adjusted using the professional knowledge and literature conducted nearby the study area. The main outputs of the WetSpass model are seasonal and annual evapotranspiration, surface runoff and groundwater recharge. Accordingly, the simulated model result shows that 77.6% of the annual precipitation is lost through evapotranspiration, 16% becomes surface runoff and about 6.4% of the annual precipitation recharges to the groundwater. The novelty of this research work is to show that the WetSpass model can be used to simulate water balance components in semi-arid and water-stressed environments provided that the model input parameters are close-fitting to the local condition. The output of this study can serve as reference for water resource experts and policymakers during planning and management of different water resource-related projects.