The Current and Future Trend of Rainfall and Its Variability in Adami-Tulu Jido-Kombolcha Woreda, Central Rift Valley of Ethiopia

Abstract

The seasonality and availability of water in Ethiopia are influenced by the steep climatic gradients and physiographic contrasts. While large population of the country heavily relies on rain fed agriculture, the anomaly in rainfall has direct implications on the crop production and further food sufficiency. This study investigates the current and future trends of rainfall and its variability in Adami-Tulu Jido Kombolcha woreda, central Rift Valley of Ethiopia. Statistical tools like; PCI, CV, and SRA method were used to identify the variability of rainfall concentration test, the degree of variability of rainfall and characterize the drought frequency and intensity. Sen’s estimator and Mann-Kendall's statistical tests were employed for trend detection. The HadCM3 A2 and B2 scenarios experiments were used for the climate projection. The current annual rainfall has increasing trends for all stations except Bulbula. However, the projection of future rainfall conditions suggest that the annual and seasonal rainfall in Adami Tulu Jido Kombolcha is most likely to decrease for both HadCM3-A2 and HadCM3-B2 scenarios, and found to be statistically insignificant at 5% significance level. The average annual precipitation concentration index (PCI) showed irregular distribution of annual rainfall for most stations except Bulbula that highlights the seasonality in rainfall distribution. Most of the stations showed moderate variation in annual rainfall (CV ranging from 20 to 30%) except for Ziway station, which has less variations (CV% < 20%). Generally, the rainfall trends in the study area are not uniform and consistent in both time and space until end of 2090.

Keywords: trend analysis, Climate Change, GCM, Scenarios, SDSM, Coefficient of Variation, HadCM3