Performance Assessment of Cascaded Reservoirs Operation Under the Impact of Climate Change the Case of Lower and upper Dabus Reservoirs, UBN Basin, Ethiopia

Jemal Ibrahim Mohammed,Bogale Gebramariam

doi:10.11648/j.ijees.20210602.12

Abstract

Globally the impact of climate change affects many water resources projects, thus it is important to assess its impact on reservoir performance. This study mainly assesses the performance of Upper and Lower Dabus reservoirs under the impact of climate change using Reliability, Resilience and Vulnerability indices (RRV). The future climate variables were projected by General Circulation Model (GCM) and downscaled at the basin level for the A1B emission scenario using the Regional Climate Model (RCM). The trend of streamflow forecasted at outlet (merging to main Abbay River) was assessed and the inflow generated to reservoirs was used to determine reservoirs performance indices (RRV). Finally the inflow to the reservoirs with monthly evapotranspiration from the reservoirs was used as input to HEC-ResSim to simulate and optimize reservoir operation and Power production. The average annual inflow to the upper Dabus reservoirs shows an increasing of 3.17% for early century (2010-2040) and decreasing of 2.08% and 4.46% for mid (2040-2070) and late century (2070-2100) respectively. The average time base reliability of the reservoirs was less than 50% for no reservoir condition and greater than 90% for the other condition considered but volumetric reliability and resilience shows 100% for all conditions. According to the vulnerability result the reservoirs will face shortage of flow which ranges from 8.85% to 88.51%. The result of reservoir simulation shows that the power plant parameters does not shows much significant in all scenarios considered in this study. As a result of these the Dabus sub-basin reservoirs have sufficient potential to produce required power for the country according to reconnaissance level study of the basin demand requirement and even more power can be produced.

Highlights

Global climate change caused by increasing atmospheric concentration of carbon dioxide and other trace gasses, as well as anthropogenic activities are expected to alter regional hydrological condition and result in a variety of impacts on water resources
The methodology used in this study includes the following steps (1) Data collection; (2) extraction of climate data series from the climate change scenarios; (3) watershed-based hydrological and reservoir operation modeling; (4) Performance assessment of reservoir water resources under standard operation policy; (5) Preparing Reservoir rule curves
The inflow to the Dabus reservoirs is generated by using the bias corrected dynamically downscaled climate variable as an input to the HEC HMS -hydrological model

Summary

Introduction

Global climate change caused by increasing atmospheric concentration of carbon dioxide and other trace gasses, as well as anthropogenic activities are expected to alter regional hydrological condition and result in a variety of impacts on water resources. Such hydrologic changes will affect nearly every aspect of human wellbeing, from agricultural water productivity and energy production to flood control, municipal and industrial water supply, and fish and wildlife management. Reasonable allocation of water resources by reservoir operation plays an important role in matching the requirements of sustainable water resources and mitigating the adverse impact of climate variations and changes. The increase in population growth, economic development and climate change have been proven by IPCC, to cause rise in water demand, necessity of improving flood protection system and drought (water scarcity)

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