Evaluation and Multi-Purpose Analysis of Omo*Gibe III Hydropower Reservoir to Include Downstream Irrigation Development

Abstract

The mam purpose of the thesis rs, to evaluate and develop multi-purpose reservoir operational rule to Gibe III dam by accurately representing the reservoir inflow from upstream unregulated and gauged catchments using HEC-ResSim model. Spreadsheet equivalent of HEC-ResSim was also developed using excel for comparison purpose. Twenty years (1986-2005) of meteorological and Hydrological data were used to simulate the inflow sequence to reservoir. The main input data to the model were the Gibe III reservoir physical characteristics, the irrigation water requirement downstream of the dam, the water balance inputs to the reservoir (net evaporation, surface inflow to the reservoirs). From the release pattern alternatives, the simulation/ optimization operation was suggested considering relatively minimum losses and maximum energy generation. The yearly average firm energy from Spread sheet at 95% of reliability was found to be 5441.37GWh/year and from HEC-ResSim was 5410.1 GWh/yr at base scenario. The results show that rule curves significantly improve the reservoir performance in terms of hydropower production without reducing the downstream safety against Irrigation requirement. To further improve the operation, real-time optimization is performed taking real-time and forecast information about reservoir levels, reservoir inflows and water demands into account. The optimization problem puts focus on the transaction between short-term hydropower and flood risk objectives and long-term penalties in terms of deviations from the optimized rule curves. The analysis demonstrates that the real-time