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.
