Evaluation of Groundwater Potential and Sustainable Management in Upper Gilgel Gibe Watershed, Omo Gibe River Basin, Ethiopia

Abstract

The demand for freshwater is increasing as the world’s population continues to grow and expects higher standards of living. Groundwater plays a crucial role in Ethiopia in providing drinking water, increasing food and agricultural production, and facilitating industrial developments. Thus, a quantitative evaluation of the resource is a pre-requisite especially in developing countries like Ethiopia, where most people rely on it as a source of potable water and domestic uses. This study focused to quantify the groundwater resource potential and assess the sustainability of groundwater reserve at Upper Gilgel Gibe watershed using water balance method. The study was commenced through defining the boundary of the project area, review of previous works and collection of valuable primary and secondary data. The analysis and interpretations of data was supported by the application of different software like ArcGIS 10.4.1, Thornthwaite monthly water balance model, Soil Water characteristics of SPAW (Soil-Plant-Air-Water) computer model, Minitab 18, XL STAT 2018, Base Flow Index (BFI+ 3.0), pcp stat and Water Balance (WTRBLN) model. Estimation of areal depth of precipitation and Actual Evapotranspiration was carried out through the use of Isohyetal method and WTRBLN model and found as 1664.5 mm/year and 911.6 mm/year respectively. A total water volume of 875,829,800 m3/year is estimated to recharge the aquifer system. The present annual groundwater abstraction is estimated as 10.15 MCM per year. The estimated specific yield, exploitable groundwater reserve and safe yield of the catchment are 5.9%, 520,557,000 m3/year and 522,768,349 m3/year respectively. The total groundwater abstraction is much less than the recharge and the safe yield of the aquifer. The renewable groundwater resources per capita, total groundwater abstraction/groundwater recharge, and total groundwater abstraction/exploitable groundwater resources are estimated as 3960.6 l/day/capita, 0.012 and 0.019 respectively. The groundwater sustainability indicators show that there is sufficient groundwater in the study area and the groundwater resources of the area considered as under developed.