Spatial and temporal drought incidence analysis in the northeastern highlands of Ethiopia

Abstract

This study investigated the space-time drought incidence in the northeastern highlands of Ethiopia using monthly rainfall data. It also aims to predict drought events for 100 years. The Standardized Precipitation Index (SPI) was used to compute the drought severity classes of rainy months and seasons at 1-, 4- and 8-months timesteps. The Mann-Kendall’s test and Sen’s slope estimator were used to analyze the trends of drought events and to determine the magnitude of change. Inverse Distance Weighted spatial analysis tool was used to illustrate the spatial patterns of the drought risk events. The study detected extreme severe droughts in the belg rainy months in March 2008 and April 1984. However, during the belg season, the year 1999 was the driest for the recorded periods. On the other hand, the extremely severe droughts were observed during the kiremt rainy months of July 1987 and 2015, August 1984, and September 2009. In general, 1984, 1987 and 2015 were the driest years recorded in the kiremt season. The study noted that the drought risk events of months in the belg season were threefold greater than that of the months in kiremt season under moderate drought intensity class. Equally, the drought risk events of months in kiremt season were threefold greater than that of the belg season under extreme drought intensity class. Complex spatial variations of drought risk events were also observed in 1-, 4- and 8-months timesteps. During the belg seasons, the southern half was subjected to more frequent drought risk events while the northern half experienced more frequent drought risk events during kiremt season. Almost the eastern half of the livelihood zones experienced higher drought frequency events than the other parts in the 8-month timestep. The observed space-time drought risk event analysis has shown a potential threat to the rainfed agricultural practices that have a great influence on the livelihoods of smallholder farmers. Hence, documentation and assessment of drought risk events based on the livelihood zones are essential for drought risk management, early warning responses, local-scale planning and food security management. Finally, the study recommended further research on additional indices of climatic variables such as evapotranspiration and soil water content.