Geology

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Browsing Geology by Author "Ayalew, Eleni"

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    Application Stable Isotopes in the Study of Lake Dynamics in Ziway-Shalla Basin (Ethiopla)
    (Addis Ababa,University, 2003) Ayalew, Eleni
    A thorough understanding of lakes hydrology is crucial before any usage of the lakes for different development works. In Ziway-Shalla basin where there is complex inlcraction between the lakes and groundwater system, stable isotope water balance method is employed in this work to estimate the grou ndwater exchange rate for the geographica lly clustered lakes of the basin. Although the stable isotope water balance method has limitation due to lack of measurement of environmental parameters, the existence of tenninal lake, Lake Abiyata in the basin gives a chance to estimate these environmental parameters that are important in groundwater quanti fi cat ion. These environmental parameters would have been difficu lt to measure. The unknown 5A, isotopic composition of the atmospheric moisture for Zi'j»'1y - Shalla basin is estimated to be -16.8%0 and the limiting isotopic composition (5•) determined to be 12.5 %0. The lakes are evaporated with respect to the present day precipitation and the surface and ground waters between the lakes are influenced by the lakes indicating the hydraulic link between surface and groundwater. The result of stable isotope water balance shows that the lakes are influenced by different degree of groundwater fl ux .The groundwater inflow to lake La ngano and Shalla is signifi cant while the inflow to lake Abiyata is minimum. The groundwater outflow from Lake Ziway is signifi cant which may become groundwater inflows to the two downstream lakes, Abiyata and Langano. Lake Langano is characterized by modest groundwater outflow next to the two terminal lakes in the basin.