Assessment of Groundwater Potential: A Case Study of Lower Gidabo Catchment, Ethiopia

Abstract

Groundwater is occurring in different geologic formations, hydrogeological settings and topographic features. Those factors mostly control the distribution and development of groundwater. The groundwater resource assessment of an area requires a carful approach of ground investigation. Exploring hydro lithological units of the catchment is necessary by using flow mechanism, hydrology, aquifer characteristics and land use land cover of the catchment. Topographically Lower Gidabo catchment is undulating and ranges from hills of mountains ranging from 1170 of low flat lands near Lake Abaya to 3200 m a.m.s.l. In this study, groundwater potential of the catchment was assessed from the view point of groundwater flow direction, aquifer characterization and recharge-discharge zone identification. This study targets to contribute detailed aspect of the hydrogeological feature of the catchment. Appropriate software‟s like Surfer 8 for generating contour maps, Arc GIS for geo referencing and mapping of the catchment and Aquifer test to identify the aquifer parameters of the catchment were used. The groundwater flow direction of the catchment was identified by using ground water level maps. The aquifer characteristics of the catchment were evaluated using surface geologic map, pump test data and well logs data of the boreholes. According to the groundwater flow lines and the contour maps supposed in the catchment, the groundwater flows from eastern parts of the highlands of the catchment towards the plain areas of the western parts of the catchment. The groundwater flow direction is commonly controlled by rainfall and topographic features. The hydraulic characteristics are variable throughout the catchment. The transsmissivity and storativity have ranged from 1*10 -3 to 1.05*10 -1 m 2 /min and 4.11*10 -3 to 8.29*10 -5 , respectively. Likewise, hydraulic conductivity of an aquifer ranged from 3.5*10 -4 to 2.91*10 -3 m/day. The major aquifer units of the area are weathered and fractured basalts. These types of aquifer formation are recognized to be good groundwater formations. According to the result perceived, the major recharge of groundwater occurs in the Easter and Northeastern highlands of the catchment, which is said to be recharging zone. However, the area situated in the western and northwestern parts of the catchment is discharge zones.