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Universitaet fuer Bodenkultur Wien (2003)

Aquifer Characterisation and Hydrochemical Investigation in Raya Valley, Northern Ethiopia

Dessie Nedaw Habtemariam

Titre : Aquifer Characterisation and Hydrochemical Investigation in Raya Valley, Northern Ethiopia

Auteur : Dessie Nedaw Habtemariam

Akad. Grad : Thesis.Doctoral 2003

Université de soutenance : Universitaet fuer Bodenkultur Wien ; Institut fuer Angewandte Geologie

Résumé
The Raya Valley is found in north-eastern Ethiopia on the western shoulder of the Afar Depression making its own trough surrounded by volcanic hills. The basin fill is mainly composed of unconsolidated material ranging from gravel to clay. The study site covers an area of 2082 km2. The main purpose of this work was to study and characterise the ground water from geological, hydrological and chemical point of view. The recharge to the aquifer was computed using the Water Balance Method. As for the findings, this research has, on the input side, found the mean annual rainfall to be 779 mm, while on the output flank the mean actual evapotranspiration to be 695 mm, the annual evaporation from lake Ashange 1204 mm, and surface runoff leaving the basin is approximated to be 60 MCM. Accordingly, the annual recharge, assuming the ground water divide to be equal to the surface water divide, is computed to be 129.3 MCM. The potentiality of the aquifers in the area has been classified from high (=500 m2/day) to weak ( ; 0.5-5 m2/day) based on the transmissivity values calculated using different methods. In general the high potentiality aquifers were found mainly on the western margin of the valley. The ground water in the study area is mainly of Ca-Mg-HCO3 or Mg-Ca-HCO3 type. In general the chemical composition of the ground water is controlled by chemical weathering of silicate minerals which make up the surrounding basaltic rocks. Some samples indicated higher than recommended values for NO3 and SO4 and these could be attributed to human interference. From geological, hydrological and chemical point of view, the Raya Valley has good ground water potential. A proper management of the prevailing potential that includes a more detailed and multi-disciplinary study with a view to further analysing the resource endowment as well as figuring out its sustainable use seems mandatory and in the interest of improving the increasing water shortage problem of the valley.

Mots clé : Aquifer, Ergiebigkeit, Geology, Raya Valley, Wasserhaushalt, / Wasserchemie — Aquifer, Geology, Hydrochemistry, Potentiality, Raya Valley, / Water Balance

Présentation : Österreichische Dissertationsdatenbank

Page publiée le 27 mai 2008, mise à jour le 13 mars 2019