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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/2457

Advisors: Dr. Seifu Kebede
Keywords: Hydrogeology
Copyright: Jun-2009
Date Added: 4-May-2012
Publisher: AAU
Abstract: The highlands falling within the project area represent part of the southeastern central Ethiopian plateau including Arsi, Bale and parts of southwestern margin of the project area also extend to adjoining areas of Sidama Zone in South Nations, Nationalities and Peoples Regional State. The Wabe river originates just east of Wetera Resa Village in South Nations, Nationalities and Peoples Regional State. All the study area is covered by Tertiary and Quaternary volcanics. Tertiary volcanics of the pre-rift and post-pift cover large part of the area. The Pre-Rift succession represented by Alaji basalt, alkali trachyte flows, and alkali trachyte and basalt flows and the Post-Rift volcanic succession including alkaline to peralkaline basalts and trachytes. The Quaternary Volcanics represented by Ginir Volcanics and basalt, often scoriaceous, with minor cinder cones and vitric tuffs. These volcanic rocks are topped by Plio-Pleistocene fluvio-lacustrine sedimentary sequence. Most central part of the area covered by Post-Rrift succession of the Nazarath group volcanic rocks. Groundwater recharge is estimated by applying three methods; base flow separation, water balance and soil moisture balance methods. Drainage-area ratio extrapolating method between the drainage area of the gauged sub-catchment and ungauged sub catchment is employed to estimate the discharge of the river at the delineated mouth of the river. Recharge estimated by flow separation method is more than seven fold greater than recharge estimated by soil moisture and water balance methods. The composition of the majority of the highland volcanic plateau is silicate minerals of mostly plagioclase feldspars of the albite and anorthite group and pyroxene composition. These minerals are rich in Ca, Mg and Na. Hydrolysis, decomposition and/or leaching of these silicate minerals enriches the water in the highlands by Ca, Mg, and Na cations. In the study area most water types obtained from laboratory analyses have low TDS and based on cation composition Ca-Na-HCO3 is the dominant water type followed by Na-Ca-HCO3 evolving down the flow path to dominantly Na-Ca-HCO3 water. Concerning water quality criteria for drinking and irrigation purposes the water from the area fits the standard quality.
URI: http://hdl.handle.net/123456789/2457
Appears in:Hydrogeology

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