Meteorological Drought in Northwestern Escarpment of Ethiopian Rift Valley: detection seasonal and spatial trends

Abstract

Background The Northwestern Escarpment of the Ethiopian Rift Valley has been frequently affected by droughts for decades. The area is among the most drought-prone and chronically food-insecure parts of the country. The study areas that include the Raya Valley livelihood Zone (RVLZ), Alagie-Offla livelihood Zone (ALOFLZ), and Tsirare Catchment Livelihood Zones (TCLZ) are amongst the most vulnerable and badly affected livelihood zones in the Northwestern Escarpment of the Ethiopian Rift Valley. Hence, this study aimed to monitor the meteorological drought conditions of the three LZs from 1983 to 2016 using the Standardized Precipitation Evapotranspiration Index (SPEI) at three months’ time scale. Both monthly Climate Hazards Group InfraRed Precipitations with Station data (CHIRPS) and Enhancing National Climate Service (ENACTS) temperature data (1983–2016) at moderate spatial resolution (i.e. 4 km-by-4 km) were obtained from the National Meteorological Agency of Ethiopia. Results This study uncovers seasonally recurring droughts that vary in severity, frequencies, and durations within and between the livelihood zones. The results indicated that severe drought occurred in all livelihoods zone of the study area from years 1983 to 1991, while ALOFLZ and TCLZ have recorded relatively higher drought severity. From 1989 to 2016, the severity and frequency of droughts were increased during the Belg (small rain) season but decreased in Kiremt (summer). In most of the study years, there have been Belg or Kiremt or both drought seasons in the study areas. The severity and frequencies of Kiremt drought in this study were higher from 1983 to 1991, better 1993–1998, and mildly to moderate drought from 2000 to 2016. As the frequencies and persistence of mild drought have increased, the intensity and precipitation amount are too small to cultivate crops and forage growth. This problem needs special considerations on the current moisture harvesting system and afforestation practices to reduce natural and human-induced drought impacts. Conclusions Studying drought with long recorded meteorological data from a large number and uniformly distributed meteorological grids in small scale livelihood zones had great implications to identify the real trends of spatiotemporal meteorological drought. This enabled the researchers to investigate the real drought frequencies, severity, and durations in small scale areas. The study will support to improve the existing drought monitoring system and to build resilience to drought at the household level. The finding also will have a significant contribution to early warning systems, particularly at district levels. Ended, it needs to consider solutions for short and long drought impacts. The agricultural sector should consider the long-cycle crop growth patterns to reduce crop failures and forage problems.

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