SPATIAL GROUNDWATER RECHARGE ESTIMATION AT SHINILIE WATERSHED, EASTERN CATCHMENT OF AWASH RIVER BASIN

Abstract

Sustainable groundwater management requires knowledge of recharge. Recharge is also an important parameter in groundwater flow and transport models. Spatial variation in recharge due to distributed land-use, soil texture, topography, groundwater level, and hydro meteorological conditions should be accounted for in groundwater recharge estimation. However, conventional point-estimates of recharge are not easily extrapolated or regionalized. In this study, a spatially distributed water balance model WetSpass was used to simulate long-term seasonal recharge using land use, soil texture, topography, and hydro meteorological parameters in Shinilie watershed, a semiarid region of Ethiopia. WetSpass is a physically based model used mainly in estimation of the long-term average spatial distribution of surface runoff, actual evapotranspiration, and groundwater recharge. From the result, it is found that the long-term temporal and spatial average annual rainfall of 700 mm was distributed as: surface runoff of 175 mm (25%), evapotranspiration of 484 mm (69%), and recharge of 42 mm (6%). This recharge corresponds to 1068l/s for the 802.96 km2study area. Most of the well that used for Dire Dawa and Harar water supply exist in this watershed are located in the areas of low to medium groundwater recharge areas. Therefore, there should be shifting of the well location to the high recharge area by considering the topography and aquifer property in order to get better well yields.