Aquifer Property Evaluations and Sensitivity Analysis of Akaki well Field, Central Ethiopia
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Date
2018-10
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Addis Ababa University
Abstract
Groundwater is essential resource which used in many aspects of life activities. Ethiopia has abundant potential of groundwater resource and in resent two decades the development of this project is increased. Addis Ababa water demand highly increases due to fast population growth, urbanization and industrialization. To supply this need the Akaki ground water well is one of the well field which can meet more than 30% of water supply demands in Addis Ababa. However, a number of wells in Akaki well field get dry and become unproductive. Therefore, this study aims to evaluate and analyses the performance and aquifer parameters (transmissivity and storativity) using the theoretical model: Cooper-Jacob method and Theis Recovery method with corrected observed time-drawdown, step-drawdown, time-residual drawdown or recovery data. The evaluated result shows, most of aquifer transmissivity is underestimated and few of it overestimated when it compared with WWDSE report. Again, to analysis sensitivity of the aquifer of the study area it modelled by MODFLOW through different scenarios of-50%, -25% decrement and +25% and +50% increment of discharge and hydraulic conductivity. Also, by discounting general boundary head, constant head, rivers and Akaki well phase IIIA extraction analysis are taken. Accordingly, the aquifer system of Akaki well fields is more sensitive for the probable change of the hydraulic conductivity special during the reduction of ability to permit water through it. Concerning on the water budget of each scenario for ignorance of water packages, the simulated head of area is more sensitive for Akaki river ignorance and as the Akaki well field phase IIIA stop water pumping the other well field phase start to rise, this show the cone of depression is extended up to the phase IIIA field area and this implies there is the well interference between the phases. Those result suggest that un safe yield of water rate costs the high depletion of the water level which cause to the drying of wells and ground water depletion where ground water extracted at rate faster than it can recharge (hydrological imbalance) and sustainability of the resource is under risk.
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Groundwater, aquifer, drawdown, safe yield, sensitivity