IRRIGATION RESERVOIR OPERATIONAL PLANNING FOR HYDROPOWER DEVELOPMENT: THE CASE OF GIDABO RESERVOIR, ETHIOPIA

Abstract

Electrical energy is an integral component of the overall development of any nation. Most rural populace does not have access to electricity and the shortages of electric energy production especially in small rural areas hinder the development of rural livelihood. This study primarily intends to undertake only a rapid technical assessment that provides some basic information that essentially helps in making unbiased technical decision on the viability of the proposed energy production from Gidabo dam which had not been planned or designed with the inclusion of a hydropower scheme. The conceptual rainfall runoff model chosen for this study was HBV-light (Beta Version). The model was applied to simulate flow at dam site, using split record evaluation, involving the calibration and verification periods (about 60% for calibration and 40% for verification). During calibration period, the optimized parameters which give good performance result were determined (Reff=0.74). These optimized parameters are validated. Performance of the model in the validation period was 0.68. The study also presents the work of reservoir operation and hydropower potential estimation using HEC-ResSim Model for the better operation and management of Gidabo reservoir. The study attempts to examine the complexities in reservoir operation and prepare an optimum operation plan or release rule for Gidabo reservoir. The main objectives are simulating the optimal operation of Gidabo reservoir for the proposed water demand activities by accurately determining the reservoir inflow using HEC-ResSim model and estimate the hydropower potential that can be produced while meeting the current demands at a specified level of reliability. In the simulation of Gidabo reservoir, the reservoir physical characteristics, operational characteristics, monthly water demands and the hydrological inputs to the reservoir (Net evaporation, surface inflow) were collected and configured. This study developed optimum operating rules for Gidabo reservoir by using the application of HEC-ResSim model and estimates the optimal hydropower production regarding to storage (m3), reservoir level (m), and inflow-outflow relations of the reservoir. Based on simulation result the study evaluated the hydropower potentials of the Gidabo reservoir and found that the Gidabo reservoir can potentially generate on daily base 2.3MW and 0.2MW if the Gidabo reservoir water level is respectively placed at 1215.9m and 1212.1m above mean sea level. These levels represent the upper and the lower limits at which the proposed hydropower scheme can sufficiently release water from Gidabo reservoir to conjunctively meet the water demands for the proposed hydropower and designed irrigation purposes.