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Title: GROUNDWATER POTENTIAL EVALUATION AND FLOW DYNAMICS OF HORMAT-GOLINA RIVER CATCHMENT, KOBO VALLEY, NORTHERN ETHIOPIA
Authors: Afework, Desalegn
Advisors: Tenalem Ayenew(Prof.)
Keywords: Kobo valley
groundwater potential
recharges estimation
hydrochemistry.
Copyright: Feb-2011
Date Added: 20-Jul-2012
Publisher: Addis Ababa University
Abstract: The study aims to describe and give some detailed picture on the Hydrogeological features of the Hormat- Golina basin with more focus on the flat areas of the Kobo valley. This makes an interest from the groundwater potential point of view to evaluate its water resource potential on the basis of aquifer characterization, recharge mechanism, groundwater flow conditions and hydrochemistry of the groundwater. The basin is part of the western escarpment of Afar Rift and measures about 806 km2 areas. It is situated between 545000 to 581000m East longitude and 1315000 to 1351000m North latitude with an average elevation of 1482m.a.s.l and 2605m.a.s.l for the valley and highland part of basin, respectively. The average monthly temperature and the mean annual precipitation in the valley are 22.40C and 739mm, respectively. Potential evapotranspiration (PET) of the valley was estimated using Penman Combination method which gives annual PET value of 1596.1mm/y. Actual evapotranspiration value for the catchment estimated from Turc method gives value of 655mm. The annual surface water out flow, estimated using runoff coefficient methods resulted 98.4MCM. Chloride mass balance (CMB) method, Darcy and conventional water balance approaches were used to estimate recharge, while the average of the three values is taken as the annual recharge of the area (44.8MCM/year) which is 6.4% of the total precipitation and groundwater reserve of the valley is estimated as 2033MCM. To characterize the aquifer system of the area pumping test data, well completion reports, well logs and geology of the area were analyzed. The study area is characterized by deep groundwater systems encountered at an average depth of 141m. Their hydraulic characteristics are spatially variable, which the transmissivity of the valley ranges from 6.85 – 4510 m2/d and the mean, and median are 492.38 m2/d, and 199m2/d, respectively. Its hydraulic conductivity ranges from 0.19 – 125 m/d and the mean, and median are 10.9 m/d, and 4.25m/d, respectively. The Quaternary unconsolidated sediments are the main aquifer units in the area. These aquifers were found to be good groundwater potential zone. The general trend for groundwater flow observed from pieziometric heads is from western highland part of the area towards the plain in the direction of west to east of the study area. Piper plots, Collins bar diagram and Hierarchical cluster Analysis (HCA) were used to classify the water chemistry. Groundwater type of the area was evolved from Ca-Mg-HCO3 or Mg-Ca-HCO3 water type in the area closer to western escarpment in to Na-Ca-HCO3 water type in the eastern tip of the area. The water also was of a low sodium hazard and can therefore be used for irrigation without posing much risk to the compaction of soils.
Description: A Thesis Submitted to the School of Graduate Studies of Addis Ababa University In Partial Fulfillment of the Requirements for the Degree of Master of Science in Hydrogeology.
URI: http://hdl.handle.net/123456789/3458
Appears in:Thesis - Earth Sciences

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