McCartney M., Alemayehu T., Shiferaw A., Awulachew S.B.
International Water Management Institute (IWMI), Addis Ababa, Ethiopia; University of Bahir Dar, Ethiopia
McCartney, M., International Water Management Institute (IWMI), Addis Ababa, Ethiopia; Alemayehu, T., University of Bahir Dar, Ethiopia; Shiferaw, A.; Awulachew, S.B.
Lake Tana is valuable for many people, including the communities who live around the lakeshore, those living on islands and close to the Blue Nile River, which flows from it. The area has been identified as a region for irrigation and hydropower development, which are vital for food security and economic growth in Ethiopia. This report presents findings from an integrated multidisciplinary study that was conducted to investigate the implications of this development. The study comprised three components: i) an environmental flow evaluation; ii) a stakeholder analysis of the impact of current infrastructure and water management; and iii) computer modeling of future water resources development. The study found that existing water resources development, for hydropower generation, has modified flows downstream of the lake, reduced water levels of the lake and significantly decreased flow over the Tis Issat Waterfall. Interviews with stakeholders indicate that the changes have benefited some people but have adversely affected others. Future development will exacerbate pressure on the lake. If all the planned development occurs, the mean water level of the lake will drop by 0.44 meters (m), and the average surface area will decrease by 30 square kilometers (km2) (i.e., 1%) and up to 81 km2 (i.e., 2.6%) during some dry seasons. There will be prolonged periods of several years during which water levels will be much lower than they would be naturally. If environmental flow requirements (estimated to average 862 Mm3y-1) are maintained in the reach containing the Tis Issat Waterfall, the mean water level of the lake will reduce by a further 0.37 m and the average lake area will reduce by an additional 26 km2. Without careful management these changes are likely to have severe ecological and social consequences. Hard choices must be made about how the water is best utilized. It is important that all stakeholders, including local people, are involved in the decision-making process and benefit from investments. © 2010, by IWMI.