Water Use and Operation Analysis of Water Resource Systems in Omo Gibe River Basin
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Date
2011-05
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Addis Ababa University
Abstract
In this study, HEC-ResSim (Hydrologic Engineering Center-Reservoir System Simulation)
model was used to simulate water use and operation of existing, ongoing and planned hydraulic
infrastructures, and irrigation schemes in Omo Gibe river basin. For these purpose five different
water resource scenarios were simulated viz. Scenario-T, Scenario-A, Scenario-B, Scenario-C
and Scenario-D. Scenario-T was first set up to simulate gauged flow routing without taking into
account effects of development and a good agreement was observed between simulated and
measured flow at Karadus station. The Nash-Sutcliffe efficiency criterion obtained for the
catchment was 0.782. Following this, the model was configured to simulate the recent and
proposed development interventions on water resource. Scenario-A result showed that an
average annual energy of 780GWh/year and 1911GWh/year are produced by Gibe I and Gibe II
respectively when they are operated in tandem. Equivalent storage distribution was also
examined among reservoirs in the entire simulation period. The current study, HEC-ResSim
simulation in scenario B, has discovered that long term effects of operation of Gibe III power
plant would increase the dry season outflow and decrease in flood season outflow from the Omo-
Gibe river system. An average increase of 130% in mean monthly inflows from November to
June and decrease of 25% in mean monthly inflows from July to October was observed at
Karadus. But the mean annual outflow from the basin at Karadus will be decrease by 1.14%.
Simulation of Gibe III power plant produced an average annual energy of 6,488GWh/year and
power of 758.94MW.The firm energy and power that can be guaranteed 90% of the time are
5885GWh/year, 625.0MW respectively. The average energy obtained is close with the study
made by EEPCO. The firm energy obtained is also similar and greater than the energy obtained
during reservoir operation studied by EEPCO.
Due to upstream regulation i.e. intervention the proposed power plants, Gojeb and Hallele
Warabesa stage I and II, in the upstream Omo-Gibe basin under scenario D can increases firm
energy production of Gibe III power plant to 6023GWh (2.75%) per year with same reliability
and the average annual energy can also increase to 7587 GWh per year (by 15.66%). Moreover,
during scenario D simulation annually about 1.87BCM volume of water will be diverted into
irrigation site under full irrigation development (142,000ha) and the annual volume of water
from Omo-Gibe river system below the proposed irrigation sits will decrease by 14.15%.
Keywords: Firm Energy, HEC-ResSIM, Reservoir Operation, Simulation scenario, Karadus,
and Reservoir Network
IV
Dedication
This work is dedicated solely to my mother
Abeba Yemataw,
Description
Keywords
Firm Energy; HEC-ResSIM; Reservoir Operation; Simulation scenario; Karadus; and Reservoir Network