Abstract Title: ENSO/AMO on Spatial and Temporal Variability of Rainfall and Temperature over Awash River Basin, Ethiopia

Abstract Submitted to: HYDROLOGY

Abstract Text:

Yitea Seneshaw Getahun 1, 2, Ming-Hsu Li 1,*
1Academia Sinica (Earth System Science) and Graduate Institute of Hydrological and Oceanic Sciences, National Central University, Taoyuan 32001, Taiwan
2College of Agriculture and Natural Resource Sciences, Debre Berhan University, Ethiopia

Abstract
The community’s livelihood in Awash River Basin is vastly dependent on rainfed agriculture, but high rainfall variability and related risks are becoming more frequent and unbearable. Spatio-temporal variations of monthly, seasonal or annual rainfall and their connection to SST were analyzed. Analyzing the historical records of rainfall, temperature and SST helps to improve agricultural productivity by managing the risk caused by rainfall variability. Consistent and significant increasing trends of basin temperature and AMO SST were observed from 1986-2016. Besides, the change in point of basin temperature and AMO SST were also detected in about 1997/98 and 2001/02. The annual and JJAS change in point of temperatures were detected at 2001/2002 and the mean temperatures before the change in point were 20.58oC and 21.54oC, respectively, while after the change in point the mean temperature became 22.06oC for JJAS and 21.24oC for annual. Based on BR and SNH tests the change in point of minor rainy season rainfall was detected at 1997/98. Prior to the change in 1998, seasonal mean rainfall was 267.59mm, while after the change in point the mean rainfall became decrease to 215.09mm. The change in point was detected in downstream lowland valley stations of the basin such as Assaita, Dubity, Gewane, Erer, Awash 7 kilo, Merssa and Bati. The La Niña events increase the annual and JJAS rainfall as compared to the normal period of rainfall, but the La Niña events were decreasing the minor rainy season rainfall. The El Niño events indicated decreasing rainfall as compared to the normal periods. The change in point and decreasing signal in the minor rainy season rainfall since 1997 might be highly attributed to the La Niña events, AMO SST and local warming. Considering the significant increasing trend of temperature and significant decreasing trends of minor rainy season rainfall or declining rainfall in general, we recommend having integrated bottom-up water management strategic plans particularly for the expanding agricultural activity, agro-industries and other sectors along the basin.

Keywords: Climate Indexes, Rainfall and temperature variability, Changing point and trend, PCA