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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/2018

Title: BASEFLOW ANALYSIS OF RIVERS IN LAKE TANA SUB BASIN
Authors: Zewdie, Getachew
Advisors: Seifu Kebede (PhD)
Keywords: HYDROGEOLOGY
Copyright: Feb-2010
Date Added: 30-Apr-2012
Publisher: ADDIS ABABA UNIVERSITY
Abstract: The Lake Tana sub basin is situated on the northwestern plateau of Ethiopia at the headwaters of the Blue-Nile basin, west of the Afar depression. The drainage area of the lake is approximately 15,000 square kilometers, of which 3062 is the lake area. Topographic high surrounding the basin forces the major River systems to drain toward Lake Tana. The altitude of the basin ranges between 1765m to 3000 m a.m.s.l. The climate of the region is ‘tropical highland monsoon’ with one rainy season between June and September. The rainfall data for 23 long-term records of rainfall stations lying within or around the Tana sub Basin are used for the computation of rainfall. The Tana sub Basin receives an average annual rainfall of 1329 mm. The air temperature shows small seasonal changes with an annual average of 20˚C. The major geological formations that outcrops in Lake Tana sub-basin and its adjacent areas are Tertiary and Quaternary volcanic rocks and alluvial along the major tributaries of the Lake Tana sub-basin. Alluvial sediments have limited distribution within Lake Tana sub-basin dominant at the eastern and northern side of the Lake. The understanding and knowledge of hydrology and hydrogeologic systems is very crucial for every activities involving economic development in the Lake Tana sub basin. Groundwater recharge is one of the most important factors governing the sustainable yield of groundwater and surface water exploitation. The recharge estimation of the Lake Tana sub basin was carried out based on the principle of base flow separation using HMS – SMA for gauged catchments on daily bases. The hydrological and meteorological data used for the period of 1992 to 2006. StatistiXL Multiple linear regression was used to estimate the runoff for ungauged catchments. A level of significance of 0.05 was used for the forward and backwards stepwise regressions. Climate and physical characteristics of the catchments were used in multiple regression to predict the flow characteristics of ungauged catchments. The amount of rainfall, topographic setting and geology are the main controlling factors of climate and physical characteristics of the catchments. The groundwater contribution from gauged catchments is about 161.17mm/yr or 12.1% of the total rainfall of the basin. The ungauged catchments contribute a total of 28.18 mm/yr or 2.28% of the total rainfall of the basin.
URI: http://hdl.handle.net/123456789/2018
Appears in:Thesis - Earth Sciences

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