Analysis of Water Uses on Large River Basin Using MIKE BASIN Model (case study of Abbay basin, Ethiopia)

Abstract

This study was conducted to Simulate water allocation for major production activities (existing and planned) in the Abbay basin The study has also assess the impacts of upstream water allocation on downstream users. The reduction of flow at the border due to the implementation of the projects as compared to the existing mean annual flow of the river was also computed. Based on the accepted net irrigable area and installed capacity on the master plan documents, 17 irrigation projects covering an area of 220,416 ha of land and 4,800MW hydropower projects on the main stream have been included in the analysis. From the analysis the total water extracted for these irrigation projects was estimated as 1.624Billion cubic meter annually. The border flow volume reduction as a result of the implementation of these irrigation projects during the reservoir added scenario is only 3.04% of the estimated mean annual flow of 50.45 billion cubic meters. From the analysis the total power generated due to the development of the major hydropower projects on the main stream having an installed capacity of 4,800MW is 18432GWh per year. Moreover the water released for downstream users and ecological purpose needs due consideration for the projects of Megech, Rib, Jema, Gumera, Middle Birr, Neshi A and Negesso. Unless the flow of these projects is augmented from other downstream tributary sources, the analysis shows nil flow in the natural course for consecutive months. The total water reduction at Sudan border due to implementation those identified· water resource project is almost insignificant as compared to the total annual volume at border, and also a commented by Guariso and Whittington, 1987, ""' Ethiopia was to fully develop the Blue Nile Basin for both hydropower and irrigation, (with an estimated 6,000 Mm3 being used in Ethiopia), overall the amount of water available for agricultural use in Sudan and Egypt would increase because the river could be more easily regulated downstream,