OPTIMAL WATER ALLOCATION OF KOKA RESERVIOR FOR UPPER AWASH WATER USE ON TEN DAYS BASE

Abstract

Unlike most other river basins in Ethiopia, the water resources of the Awash River have been highly developed and utilized over the last five decades. Development, particularly of irrigation, continues today. A number of major irrigation projects are currently being built, designed or planned and it is very essential to estimate the availability of water. This research aims to optimally allocate the water in the Upper Awash irrigation schemes, and recommend a 10-day water release rule for two scenarios. It also determines the frequency of deficits in the supply of water to irrigated areas (existing and planned). The thesis compiles recent studies in the basin and meteorological, hydrological and demand data for each irrigation schemes were considered for the analysis. Water Evaluation and Planning System (WEAP) model is used for the study for optimal allocation of the river water based on equitable distribution of water. WEAP strives to maximize supply to demands sites, subject to all constraints and priorities. Rule curve of Koka Reservoir is developed for two scenarios. Thus the result shows for the second scenario that is from year 2017 the shortage seriously affect the farm which means some of the irrigation schemes will not get water at all nearly for seven irrigation consecutive ten days. Hence in order to supply the limited quantity of water during deficiency, rule is developed on 10-day bases for optimal water allocation.