The phenomenon of drought in Ethiopia: Historical evolution and climatic forcing

Abstract

This study examines drought patterns in Ethiopia's 12 major river basins from 1981 to 2018 using the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI). Both indices reveal historical drought episodes with slight variations, with significant differences in 1984, 2009, and 2015. Except for the Wabi-Shebelle catchment in southern Ethiopia, all river basins show an increasing trend in SPI12 and SPEI12 indices. The eastern and central regions experience more drought according to SPEI3. Seasonal correlations show that during the March–May rainy season, precipitation is negatively correlated with the Indian Ocean Dipole (IOD) index, while in the June–September season, it negatively correlates with Nino 3.4 and positively with IOD. The study also found that El Niño leads to less rainfall in the Ethiopian highlands, while La Niña results in more rainfall in the central and northern highlands but less in the south. HIGHLIGHTS The research assessed Ethiopia's drought conditions and their environmental implications using the SPI and SPEI, identifying significant drought periods in 1982, 1984, 1987, 1991, 1997, 2002, 2006, 2011, and 2015, with both indices showing a similar drought progression but with slight differences in severity.; The research revealed that the discrepancy between the SPI and SPEI is consistently negative. This underscores the crucial influence of temperature and evapotranspiration processes in assessing the severity of droughts.; The research evaluated the impact of multiple teleconnections on drought conditions. It was observed that distinct precipitation anomaly patterns across Ethiopia were linked to variations in Sea Surface Temperature (SST).; The results highlight the relationship of El Niño with the occurrence of drought conditions in Ethiopia, particularly its effect on cumulative drought conditions for time scales of more than 6 to 12 months. The effects of the La Niña event on drought conditions in Ethiopia are not clearly observed, as several areas experienced abnormally wet conditions during La Niña events.;

Keywords

• droughts
• ethiopian basins
• spi and spei
• teleconnections