Assessment of reasons for Yield Decrease of Water Wells in Akaki Well Field based of Design, Construction and Operation

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Addis Ababa University


Groundwater is of paramount importance for the city of Addis Ababa and the majority of the groundwater supplied to the city comes from drilled wells in and around Akaki-Kality sub city. Even though numerous water wells are built over the years, the majority of the wells fell to provide anticipated design yield. The study mapped 70 wells found in Akaki Phase I, Akaki Phase II, Akaki Phase IIIA & Akaki Phase IIIB on ARCMAP to see the spatial distribution of wells and their performance over the years. From the map, some wells were observed to perform better than their neighboring wells and some wells were found to perform worse than the neighboring wells. Therefore the research engrossed in understanding the reason behind this phenomenon mainly by focusing on the design, construction, and operation of selected wells from all phases of Akaki well field. The selected 35 wells were grouped in accordance with their performance. Data from the well-completion report was organized and analyzed to identify the possible reason for the decrease in yield. Parameters used to compare the grouped wells were depth, elevation, screen arrangement, geologic medium, filter material used, construction process, year of construction, and the drilling contractor. The result showed bottom elevation of some better performing wells is deeper than those in a worse condition which means they are tapping water from a deeper aquifer. Another finding was 60% of the study wells have 30-50% of their casing screened. Some wells perform worse than their surrounding wells because their screened section is lower. For these wells, it can be suggested to increase the screen section in accordance with the water-bearing formation. From the analysis done using the Cooper Jacob method, it was found that the majority of the wells are developed within the radius of influence of one another meaning pumping water from one well is affecting the neighboring wells. Another finding of the research is the drawdown result from single and multiple well tests which showed 100% of the wells are being affected by the surrounding wells which supports the result obtained on the radius of influence of those same wells.



Akaki Phase I, Akaki Phase II, Akaki Phase IIIA, Akaki Phase IIIB, drawdown, radius of influence, well performance, well yield