Analysis & Evaluation of Hydraulic Parameters in Akake Well Fields of Addis Ababa
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Date
2016-05
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Addis Ababa University
Abstract
Declining water levels caused by withdrawals of water from well in Akaki , the
southern part of Addis Ababa have raised concerns with respect to the ability of
the aquifer system to sustain production . As the aquifer of akaki in particular is
heavily used in this area , understanding the hydraulic parameters of the area is
essential for efficient sustainable management of the groundwater resource . A single
well test was conducted to estimate the hydraulic parameters of the aquifer. An overview
of the hydraulic parameters estimated for the 12 wells in the study clearly show strong
evidence of inappropriate estimation. Thus this study was conducted to identify the
possible miss-interpretation of the observed time-drawdown , step-drawdown , timeresidual
drawdown based parameter estimation . After data quality checking , appropriate
data correction for partial penetration and unconfinedness (if exists) were conducted.
Then the standard methods like Theis curve fitting, Cooper-Jacob methods for timedrawdown
data & Theis recovery method for time-residual drawdown data were used
for parameter estimation. Beside Aquifer test v3.5 software was also used to verify the
results of the original study. Evaluation and analysis result showed that out of the 12
well analyzed , 11 transmissivity values used in the well yield estimate were
overestimated (on an average of twenty times ) and one underestimated (fivefold) ,
such highly over estimated transmissivity value misleads the designers & operators in
fixing the well yield . Therefore, in this evaluation it is recommended to conduct
multiple well test to determine the actual hydraulic parameters of the aquifer in
order to obtain the safe yield of the wells which is intended to prolong the
productivity of the aquifer and to delay excessive loss of saturated thickness .
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Keywords
Addis Ababa Water Supply, Akaki Well Field, Single Well Test, Transmissivity