Hydraulic Engineering

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Browsing Hydraulic Engineering by Subject "Addis Ababa Water Supply"

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    Analysis & Evaluation of Hydraulic Parameters in Akake Well Fields of Addis Ababa
    (Addis Ababa University, 2016-05) Dereje, Endalkachew; Mebruk, Mohammed (PhD)
    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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    Assessment on Interpretive Technique of Transmissivity and Storativity on Aquifers: Case of Legedadi Deep Wells.
    (Addis Ababa, 2016-05) Borga, Saberi; Mohammed, Mebruk(PhD)
    Urban part of our country has seen a very dramatic expansions and population growth in the past two decades. Addis Ababa is one of the major city that’s affected by this expansion and population growth. Due to this the water supply demand for the city has also increased dramatically. To meet this ever growing demand Addis Ababa Water Supply and Sewerage Authority has been developing groundwater around Addis Ababa area. One of these groundwater developments is in Legedadi well fields. The Legedadi well field’s yield capacity is estimated to be around 45,000m3/d. This potential will be harvested by development of 40 deep wells in the area of which 10 deep wells have been constructed and tested around Legedadi Legetafo Ayat areas. This ten wells have been drilled with average depth of 300m and are sparsely located over the Legedadi well filed. The currently drilled and developed ten well in the well fields do not have an observation well thus, they are considered as a single well tests. The drawdowns for each of the well is measured in the drilled well itself and the analysis is based on this drawdowns. The fact that effects of partial pentation and well head loss have not be counted in the analysis of the wells caused the transmissivity and storativity to vary greatly form the true aquifer nature in the Legedadi well fields.The two major emphasise that was given in this research when trying to determine the transmissivity and storativity using the Copper-Jacob method, Theis method and recovery method is the well efficiency and the effects of partial penetration of the wells. When the well efficiency was determined for the wells, for two wells there efficiency fail drastically below the accepted range of well efficiency and grater partial penetration effect was observed in two other wells. When this three methods are applied to this for the observed and drawdown data the result of the transmissivity and storativity greatly differ from the values that’s is determined when the head loss in the well is considered using the well efficiency or effect of partial penetration. Thus this indicates the well to be over pumped or underestimate in some case in this ten wells. Key words: - Addis Ababa Water Supply, Legedadi Well Fields, Partial Penetration, Storativity, Transmissivity and Well Efficiency
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    Evaluation of Hydraulic Parametersi n Case of Akaki Wells on WF02-PW16 aND WF02-PW17 Wells
    (Addis Ababa University, 2021-10) Solomon, Lake; Daniel, Fikresilassie (PhD)
    The term groundwater is usually reserved for the subsurface water that occurs beneath the water table in soils and geologic formations that are fully saturated. In recent decades it has become apparent in many countries of the world that groundwater is one of the most important natural resources. So far, in Ethiopia, groundwater is mainly utilized for the water supply purposes. It takes care at present of 70% of rural water supply and plays a major role in several of the largest cities (Addis Ababa, Dire Dawa, Mekelle, Bishoftu, and Harari) and a number of medium-sized towns. As capital of Ethiopian, Addis Ababa has seen greater expansions and urbanization than other major city in the country. The primary objective of this project is evaluation of pumping test data to determine the hydraulic parameter of the Akaki phase IIIA bore holes in case of WF02-PW16 and WF02-PW17 by using Theis curve matching method, Cooper Jacob and recovery method on excel sheet and aquifer test software. Akaki well phase IIIA on WF02-16, WF02-17 Wells is located between 8°45' 20" to 9°13' 17" N latitude and 38°34' 3" to 39°4'10" E longitude in Oromiya Regional State, Akaki Kality Sub city south of Addis Ababa about 20 km from the city center. Akaki well field is one of the water supply projects implemented to alleviate the prevailing unsatisfactory water supply situation at the capital city, which is an important service for one of the most water deficit areas of the city-western & central Addis Ababa. The transmissivity values obtained in this project has great variation from the study of WWDSE which accounts for 5 to 100%. These two wells analyses results have overestimated. The overestimated Transmissivity envisions good aquifer with better yield than the capacity of the aquifer.
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    Well Failure Assessment: The Case of Akaki Phase Iiib Well Field
    (Addis Ababa, 2017-06) Edris, Sofia; Mohammed, Mebruk (PhD)
    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