Trend and temporal variation of droughts in East Wollega Zone, Western Ethiopia

Drought is one of the most serious environmental, social, and economic issues facing the world today. This study looked at the pattern and temporal variation of drought in East Wollega Zone, Western Ethiopia, from 1981 to 2017. The daily rainfall and temperature data of seven stations for 37 years (1981–2017) were collected from National Meteorological Agency of Ethiopia. The study utilized multi-index approach drought indexes such as Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI), Rainfall Anomaly Index (RAI), Palmer Drought Severity Index (PDSI), Deciles Index (DI), Reconnaissance Drought Index (RDI), Percent Normal Precipitation Index (PNI), Z-Score (ZSI) and Precipitation Concentration Index (PCI) using R and DrinC software. The result of the study revealed a declined trend of rainfall, while the trend and frequency of drought increased. All of the drought indexes agreed that the years 1999–2005 were the worst hit by drought. The trend of annual rainfall deviation from normal was increased while it was decreased on seasonal basis. The temporal precipitation distribution of the area was moderate for 22 years (59.46%) and irregular rainfall distribution for 15 years (40.54%). The diminishing rainfall and increased trend and frequency of drought should be taken into account when making agricultural system decisions and planning adaptation in the area.