EVALUATION OF AN EXISTING AND FUTURE WATER BALANCE, AND SCARCITY IN GUDER WATERSHED, RIFT-VALLEY LAKES BASIN, ETHIOPIA

Abstract

All types of life on earth, from plants to the smallest organisms to animals and humans, need water. The main objective of this study was to evaluate existing and future water balance and scarcity in the Guder watershed. The annual activity level, annual water use rate, and supply data are used to evaluate the current and future water demands and rainfall data is used to model drought year. WEAP is employed to model existing and future water balance based on four different scenarios: reference, high population growth, irrigation expansion, and climate change. The future annual water supply projected in the reference scenario was 29.7 MCM, and the annual average water demand was 83.4 MCM. However, the annual unmet water demand would started in 2022 due to the shortage of water. The future average monthly-unmet water demand under the reference scenario, high population growth, and irrigation expansion scenario to be 2.14 MCM, climate change scenario impacted at 24.2 MCM. Modeling of 3 months of standard precipitation index (SPI) for each of the three seasons (FMAM, JJAS, and ONDJ) has been done using the interpolation distance weighted method (IDW). A 3months SPI time scales curve gave April 1990, July 1997, and December 2016 as water-scarce years and categorized them as Normal, moderately dry, severely dry, and extremely dry. Different alternatives, such as optimizing the efficiency of irrigation water use, building storage dams, overall demand management strategies, and maximizing ground water in the watershed were suggested to reduce unmet demands. These strategies are also suggested to mitigate water scarcity and increase water availability for effective use. Therefore, employ the results of this study as techniques for the management of water resources and predicting droughts.