Characterization of the Groundwater Systems and Aquifers in Jerer Valley, Somali Regional State, Eastern Ethiopia
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Date
2015-06-06
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Addis Ababa University
Abstract
The Jerer valley which is part of the Shebelle river basin covers an area of 10,816 km2. It is located between the geographical coordinates of 7˚56'79"N to 9˚61'23"N Latitude and 42˚58'04"E and 44˚31'60"E Longitude.
The mean annual rainfall is 507.42 mm, while average monthly temperature is 26 oC. PET and AET are estimated to be 1218.3 mm and 498.4 mm respectively.
The general objective of the research is to evaluate the hydrogeological characteristics of groundwater systems concerning aquifer type, groundwater recharge estimation and groundwater flow dynamics. To meet the objectives, multiple methodologies and approaches have been applied in the area of investigation including intensive literature review, primary and secondary data compilation and historic data analysis is carried to observe the past trend of the hydrologic and hydrogeological systems.
In this research, the aquifer systems have been characterized from an area of high permeable to an area of very impermeable. Boreholes tapping water from Adigrat sandstone and Hamanlie formations were identified the best aquifers in the study area.
Groundwater recharge to these aquifers which is most possibly from precipitation on the northwestern mountains has been estimated to be about 13 mm/year. The observed regional groundwater flow has the same trend as surface water flow; towards southeast.
The geochemical data of dissolved major and minor constituents in the groundwater samples indicates the main processes responsible for the geochemical evolution are: (1) sea water intrusion; (2) leaching process of underlying rock mediated by pH; (3) Minerals weathering process and (4) dissolution of carbonate minerals characterized by high loadings of Ca, and Mg.
The research recommends the need for additional hydro-meteorological stations as well as detailed hydrogeological study in the area.
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Characterization, Groundwater Systems, Aquifers in Jerer Valley, Somali Regional State, Eastern Ethiopia