Well Failure Assessment: The Case of Akaki Phase Iiib Well Field
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Date
2017-06
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Addis Ababa
Abstract
The vast expansion of the city increase the shortage of water and Addis Ababa Water and Sewerage Authority has implemented the short term and medium term plane to overcome the deficit occurred in the city. The plans implemented are the development of groundwater and the expansion of Legadadi Dam. Even if these projects are functional the shortage of potable water has not yet been solved as many of the developed groundwater has a failure problem and decline in the yield. Among the failures observed were the wells in Akaki Phase IIIB development. Identifying the reason behind the failure problem will not only bring about a solution to the problem but also become a lesson for future well development. Thus research tries to find out the reason of malfunction and the decline of the yield of the developed groundwater of Akaki phase IIIB. For the analysis the current situation of the wells in the field and the primary data used in the hydraulic parameter and well yield estimation were collected and scrutinized. Accordingly the efficiency and the yield of each well were obtained from step drawn down test and the transmissivity of the aquifer were estimated from time draw dawn and recovery test analysis. These values at first were compared with the adopted efficiencies, yields and transmissivity values for the possible identification behind well failure.
From the analysis for 8 wells the efficiency obtained from step drawdown test is less than the value assigned in their design report which brings about inappropriate yields and transmissivity estimation. This indicates that the recommendation in the design report were inappropriate and do not represent the capacity of the well. Besides for almost all of the investigated 11 wells the estimated transmissivity has 10% to 120% variation from the values in the design report. The result clearly show that the standard procedure of adopting single well test for study and design will bring about error in the yield estimation which in turn bring about failure as long as the operation follows the result of such study approach.
Key Words: - Addis Ababa Water Supply, Akaki Phase IIIB; Single well test; Transmissivity; well failure; well Efficiency and well yield
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Keywords
Addis Ababa Water Supply, Akaki Phase IIIB, Single well test, Transmissivity, Well failure, Well Efficiency and well yield