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Title: Climate Change Impact on Surface Water Sources of Addis Ababa A Case Study in Legedadi-Dire-Gefersa Catchments and Reservoirs
Authors: Girma, Endalkachew
Advisors: Dr .Semu Ayalew
Keywords: Calibration
Climate change
Reverse water balance
Reservoir inflow
Copyright: Jan-2012
Date Added: 31-Jul-2012
Abstract: Climate change is the sever problem that the whole world is facing today. It is now widely accepted that climate change is already happening and further change is inevitable. The three catchments under consideration the Legedadi, Dire and Gefersa catchments are all situated in the upper north western Awash sub basin. The water supply to Addis Ababa Metropolitan Area is presently supplied from four sources and three directions. It has been clearly seen that climate has huge influence to impose on the water availability of the water sources of Addis Ababa by bringing seasonal shift to the rainfall pattern resulting a change in the magnitudes of the hydrologic components of the reservoirs. The main objectives of this study are reassessment of water potential of the three catchments by reverse water balance approach and the evaluation of climate change effect on the catchments and reservoirs. The hydrologic and climatic data‟s of the catchments are considered for water balance analysis of the three reservoirs. The hydrologic model calibration and validation is carried out for both daily and monthly time steps. In monthly base the model performance is well to simulate the generated flow (by reverse water balance). The projected daily mean, maximum and minimum temperature of the Legedadi, Dire and Gefersa shows an increasing trend in comparing with respect to the observed period. The projected areal rainfall also shows an increasing trend in both future time horizons of Legedadi,Dire and Gefersa catchments. Evapotranspiration also shows an increasing trend in all catchments. In Legedadi catchment the future surface runoff at both time horizons shows increment by 14% and 15.75% increase in 2030‟s and 2090‟s time horizon respectively. In the case of Dire catchment surface water potential increases by 9% and 3% respectively in 2030‟s and 2090‟s time horizons respectively. Gefersa also shows increase in surface runoff in both time horizons by showing 5% and 3.8% increase in 2030‟s and 2090‟s time horizons respectively. Finally, it is seen that all the three catchments are in favor of climate change (increasing trend of surface runoff) so that all are expected to generate water beyond the capacity of the dam. The effect of climate change on the three reservoirs storage and expected spillway discharge was evaluated and the three reservoirs have a tendency of increasing reservoir storage and spillway discharge in both future time horizons. Therefore, it is recommended to increase the storage capacities and treatment plants in order to utilize the surface water potential of the three catchments.
URI: http://hdl.handle.net/123456789/3534
Appears in:Thesis - Civil Engineering

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