ASSESSMENT AND EVALUATION OF MICRO TO SMALL HYDROPOWER POTENTIAL SITES IN AWASH RIVER BASIN

Abstract

The Awash River Basin, covering an area of about 112,696 km"2, is located in the central portion of Ethiopia. The mean annual rainfall of the basin is estimated to be _737mm but the mean annual rainfall of the western region which mostly contributes to the basin water resources, is about 850mm. The rainfall broadly varies from about 1200 mm in the southwest to about 300 mm in the northwest. The Awash River traverses a distance of nearly 1250km and falls through a level of 2750m.The average slope of the river is nearly 2.2m/km.The effective area of the basin from the point view of water resources contribution is only about 61000km2 which is about 54% of the total basin area. Different years of record of stream flow of 17 gauging stations in the basin have been collected from Ministry of Water Resources, Hydrology Department and the missed data of the stations have been filled using correlation approach prior to data extension and data transfer. Stream flow data of some of the stations (those with less than 15 years of record) have been extended and then the stream flow data of the gauged stations have been transferred to the interested potential sites by area-ratio method to determine design discharges of different dependability used for potential power calculation. In the study,33 potential sites were selected and gross power potential from all sites were estimated using the available potential head and stream flow after presenting in flow duration curves. The gross potential is found to be 456 MW (3995GWh of energy per year), where as the total potential power and energy output of the sites, by monthly In order to facilitate favorable condition for local decision makers as to which sites should be given top priority, ranking of the sites was carried out based on the ranking value of the most influencing parameters ; average annual discharge, gross head, accessibility and distance of the sites from the demand center ( near by towns). Accordingly, AW-15 for Tendaho town is the most promising site, AW-26 for Aleltu town is the second, A W-8 is the third for Addis Hi wot town and A W-13 for W eranso town is the least potential site. Moreover, these potential sites have been ranked based on their unit costs of energy production in which A W-2 for Lemen, A W-4 for Ombole, A W-8 for Addis Hiwot and A W-11 for Awash towns are the first four promising sites. The future demand of electrical energy of the area (basin) has been estimated based on energy coverage or contribution of the basin and compared with the potential supply of the assessed potential sites and existing schemes. In addition, both the moderate and target peak power demands of the demand centers (nearby towns) have been forecasted and compared with the generation of the corresponding nearby potential sites.