Assessing the Impact of Climate Change on Drought Characteristics in the Central Rift Valley of Ethiopia

Bereket Deselegn, Tewodros Assefa Nigussie,* and Tewodros Tesfaye

Abstract

The understanding of past and future droughts is vital for the development and management of water resources at certain area. Thus, this study assessed climate change's impact on meteorological drought based on the Standardized Precipitation Index (SPI) in the Central Rift Valley of Ethiopia. Rainfall data of nine stations for the period of 1985-2019 (historical) were obtained from the Ethiopian National Meteorological Agency. Projected rainfall data of Representative Concentration Pathway (RCP) scenarios under HadGEM2-ES were obtained from the CORDEX-Africa database selected for the years 2020-2049 (near), 2050-20779 (mid), and 2080-2100 (far future). The computed SPI values were, then subjected to frequency, intensity and Mann-Kendall (MK) and Sen’s slope-based trend analyses. Accordingly, based on SPI-3 values, 325 moderate, 141 severe, and 87 extreme drought events were identified in the historical period. Similarly, for the near future, 392 moderate, 171 severe and 95 extreme drought events were identified under RCP4.5, and 456 moderate, 184 severe, and 98 extreme drought events were identified under RCP8.5 scenarios for the far future. MK trend test showed about, 69% no trend and a 19% decreasing trend at 95% confidence level in the historical period. RCP 8.5 showed a significantly decreasing trend with the S-test of -158 and Z = -1.98 in near future and (S-test= -122, Z=-2.3) in the far future. But, RCP4.5 showed decreasing trend in the mid-future (S-test=-178, Z= -2.1). In general, the results showed that drought increased in intensity, severity and duration in the historical and future periods under RCP4.5 and RCP8.5 scenarios.