Analysis Models of the Emptying Curves of five Selected Springs in Addis Ababa
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Date
2007-07
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Addis Ababa Universty
Abstract
The use of springs as a community water supply source in Addis Ababa dates
back to the very early times of the establishment of the city. Other surface and
ground water sources (dams and water wells) have also been constructed in its
later development stage. No matter how big the newly developed sources are, it
is true that spring sources are still in use. This justifies the importance of these
sources as a means of potable water supply and invites for further detail
investigations.
Identification of springs with sustainable flow has been a pre requisite prior to
construction. Analytical flow modeling of springs with has a lot to provide in
answering this question as it helps to understand the flow and storage
conditions of a spring source.
In this study an attempt was made to analyze the emptying curves of six
springs in Addis Ababa of which collected data have permitted the analysis of
five of them. The analysis is based on monthly discharge monitoring of the
springs for one hydrologic year. Water sampling has also been conducted from
each spring for the determination of seasonal water quality changes. Recession
curves were identified from the plot of the monthly spring discharge, from
which flow and storage parameters were calculated. The main parameters of the
sources have been estimated using the formula developed by Mangin (1970).
From the analysis of the curves, it was possible to extract information on the
contribution of rainfall to the spring discharge, storage conditions of the spring
reservoir, the recharge conditions (rate of recharge) and the current reserve for
sustainable flow. The method is applicable even to very small discharge springs.
This has been considered as a means of identification of sustainable springs
prior to construction.
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Keywords
Springs in Addis Ababa