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Title: Hydrogeology of the Borkena River Basin Wollo - Ethiopia
???metadata.dc.contributor.*???: Dr. G. Bonardi
Mr. A.S.M Rao
Tadesse, Ketema
Issue Date: Jul-1980
Publisher: Addis Ababa University
Abstract: The Borkena River Basin is located in Wollo governorate general, it is part of a major graben related to the Ethiopian Rift System, which extends north to Korbeta graben around Maichew and south upto Debre Berhan, and approximately stretches in a north-south direction; there are significant contrasts of topography in the basin where the structural control is very strong. The hydrology of the area varies in different parts of the basin, Consequently, the hydrogeology of the basin also differs, such that there is a great potential of groundwater in the flat low lying alluvial sediments while a less significant ant amount exists within the volcanic rocks forming the uplifted borders of the graben, Several springs with discharges of less than 5 lit/sec. occur in the area issued from the volcanic rocks. There are eleven water supplying drilled wells in the area, seven located in the alluvium aquifers and the remaining four on basaltic aquifers; Pump tests have been carried out in some of the wells which gave transmissibility coefficient of 91+ to 28 .1 m3 per day per meter. However, it was impossible to calculate the coefficient of storage, a significant parameter which measures the volume of water, the aquifer releases or takes into storage, Proper chemical analysis of both the ground and surface waters carried out in the area show low total dissolved solids. All of the samples in the area have loss than 1000 mg/1 (1 mg/1 = 1 ppm) dissolved solids, except for the hot spring waters, Fow of the bacteriological tests of the waters in the area show low patho­genic organism though most of the water samples, (particularly the groundwater’s) contain high nitrate content, The water balance for the area has been determined, The total annual rainfall calculated on the basis of the mean annual preci­pitation for the basin is 1846.41 x 106 m3. The groundwater recharge for the area has been calculated based 0n the evapotranspiration data at Cheffa, where the water loss is maximum to approximate the minimum infiltration, and amounts to 185.11 x 10 m. This is 10.02% of the precipitation. The actual evapotranspiration in the area amounts to 872, 834.8 and 836.1 mm, for Cheffa, Dese and Kombolcha respectively. 218.55 x 106 m3 of water leaves the basin at the Borkena River outlet as runoff and is equivalent to 11.83% of the precipitation.
Description: A Thesis Presented to The School of Graduate Studies in Partial Fulfillment of the Requirements for the Degree Master of Science in Geology.
Appears in Collections:Thesis - Earth Sciences

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