Water Balance Estimation Using Integrated GIS-Based WetSpass Model in the Birki Watershed, Eastern Tigray, Northern Ethiopia

This study aims to estimate long-term average annual and seasonal water balance components for Birki watershed using WetSpass model with the integrated geospatial modeling approach with ten years’ hydro-meteorological and biophysical data of the watershed. Both primary and secondary data were collected using both field survey and disk-based data collection methods. The WetSpass model was used for data analysis purposes. The finding showed that in the summer season the annual groundwater recharge is 24.1 mm year-1 (96.5%), winter season mean groundwater recharge is 0.8 mm year-1 (3.5%) and yearly mean groundwater recharge is 24.9 mm year-1, Surface runoff yearly mean value is 40.6 mm year-1, Soil evaporation yearly mean value is 10.8 mm year-1, Evapotranspiration yearly mean value is 60.8 mm year-1, Intersection loss yearly mean value is 17 mm year-1, and Transpiration loss yearly value is 6.8 mm year-1 in the entire watershed. The mean annual precipitation, which is 573 mm, is contributed to 7.4%, 7.1% and 85.5% recharge to the groundwater, to surface runoff, and evapotranspiration, respectively. Annually 1.1205 million m3 water recharges into the groundwater table as recharge from the precipitation on the entire watershed. The contribution of this study could be used as baseline information for regional water resource experts, policy makers and researchers for further investigation. It can also be concluded that integrated WetSpass and GIS-based models are good indicators for estimating and understanding of water balance components in a given watershed to implement an integrated watershed management plan for sustainable utilization and sustainable development.