Evaluation of Hydraulic Parameters in Kobo Irrigation Wells
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Date
2016-06
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Addis Ababa University
Abstract
The study area of this research is Kobo Valley catchment, situated south of Raya Valley
in Northern part of Ethiopia. The low lying inter mountain valley part of the area is
known by its high groundwater potential and semiarid climate. Currently, it is
underground water source exploitation and investigation mainly for irrigation because of
scarce surface water and low annual rainfall. In the study area 17 single well constant
pumping test and recovery test data were collected besides 14 of 17 wells have the step
drawdown test data. In this research where conducted to re- analyze the transmissivity
value estimated for design. Having checked the data quality for all 17 wells in the Kobo
well field transmissivity was estimated using Theis and Cooper-Jacob method for the
time drawdown data collected and the residual drawdown analysis time residual
drawdown data. For each well three transmissivity value were estimated the geometric
mean value estimated ranges from a minimum of 26m2/day to2790m2/day. For the
same wells the range of transmissivity value used in the design of the kobo irrigation
scheme was 55.2m2/day to 3145m2/day. Among the 17 wells 11 wells were found to
under estimate transmissivity obtain in this research 4- 82% but one are found to
overestimate the transmissivity with 8-178%.given the fact that both this research and
the design document uses the same well test data, such huge variation in the estimation
could only because by data interpretation techniques. Appropriate data correction shall
be made test for any well analysis for hydraulic parameter estimations. In well data
obtained for single well test such correction is even more vital. For the well with under
estimated transmissivity values the well yield could have been larger conversely for over
estimated transmissivity values will not supply the estimated yield.
Key words: -kobo pressurize irrigation project, pumping test, single well test,
step drawdown test
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Keywords
Kobo Pressurize Irrigation Project, Pumping Test, Single Well Test, Step Drawdown Test