Abstract

El Nino/Southern Oscillation (ENSO) is one of the most important and best characterized mechanisms of global climatic variations impact on the surface water. It has tremendous impacts on local, regional and global climatic conditions by disordering the normal patterns. Tropical water resource is very sensitive to climatic anomalies that jeopardize the performance of power generation capacity by generating water shortage during El Nino years. Ethiopia is confined within the tropics and hydroelectric power generation was depending on water, but this condition same time unpredictable due to climate extremes i.e. flooding and drought that was related in ENSO phenomena. The koka dam hydropower project site is confined in Ethiopia. Climate of this region is highly influenced by global circulation patterns that govern the local climate. Therefore, during El Nino years the stream flow and runoff fluctuation of Awash river shows strong reduction. The study results revealed that ENSO has played a great role in modulating the seasonal rainfall over the upper, middle and lower Awash river which in turn influences both the stream flow and runoff. In particular, it has induced power fluctuation problem over the Awash river that significantly affect the quality and quantity of hydroelectric power generation as well as the user of this river for cultivation and other purpose. In view of this, we propose that skillful early warning can be well practiced by acquiring appropriate lead time climate based forecasting of on the possible occurrence of extremes weather events stream flow and runoff fluctuation.

Keywords: ENSO; Runoff; Stream flow; Awash basin; Fluctuation