Upgrading and Rehablitation of An Existing Water Supply Schem The Case of “Midmar Embankment Dam “
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Date
2011
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Addis Ababa University
Abstract
Midmar dam was designed as water supply source project for Adwa, small town named Adi-Abun (Currently merged with Adwa town) and for Almeda Textile Factory. However, recently, the dam is also serving as water supply source for Axum town which was not considered during designing phase, Hence, the main objective of this paper is to evaluate the existing and suggest possible remedial engineering measures so as to harvest maximum water as much as possible in a hydrologic year as well as comparing the harvested water with future water demands.
SEEP/W software model is used to analysis quantity of seepage through dam body and foundation at both scenarios (At existing condition and with design modification), when compared with the quantity of seepage estimated at the design document, the designed documents has no problem.
SLOPE/W model is used to computed slope stabilities at different scenarios under different loading conditions as per the analysis results at the existing condition the dam is more stable and the result of SLOPE/W for modified ( after dam height increment by 2m ) shows that the dam is still safe and stable.
As per water demands for Adwa and Axum towns at the existing condition Midmar dam can serve up 2023 G.C safely and when modified as a result 2.5 MCM volume of water can be stored additionally, that is more than 33 % increment in water holding capacity of the dam has been achieved and therefore the dam can serve as water supply source up to 2033G.C safely.
Design modification for existing spill way is not found as such satisfactory as upgrading option as per the second upgrading option additional 22.39ha can be inundated, therefore social, environmental and compensation issues should have to be kept in mind.
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Keywords
Designing phase, Hydrologic year