Drought Occurrence Pattern in Tigray Region, Northern Ethiopia

A.S Tefera,N.J Bello,J.O Ayoade

doi:10.4314/jasem.v23i7.23

Abstract

Drought is characterized using parameters including duration, severity, intensity and spatial coverage. Drought frequency and trend can also be used as additional parameters to further characterize drought occurrences. In this study, drought occurrence was examined using Standard Precipitation and Evapotranspiration Index (SPEI) as an assessment tool. Based on the SPEI results, spatial and temporal patterns were inspected both at district and regional levels. In doing so, monthly climate data collected on selected stations, from the Dutch national weather service known as the Royal Netherlands Meteorological Institute (KNMI), was used to assess the drought trends and characterize the study area in terms of drought duration, severity, intensity, frequency, spatial extent as well as drought trend. The analysis results indicated that most districts in the southern and eastern zones experienced more intense droughts than the rest of the study area. It was also found that the average drought return period in the study area ranged between 2.02 at 3-month, 6-month and 24-month time scales to 2.13 years at 12-month time scale. A statistically significant increasing drought trend was also revealed at all-time scales. Generally, the study has revealed an increasing trend of drought occurrence and spatially variable drought duration, severity, intensity and frequency in the study area. The short return period and increasing drought trends indicate the need for urgent drought management intervention.Keywords: Drought characterization, Drought Intensity, Trend, Spatial Distribution,

Highlights

MATERIALS AND METHODSStudy area: This study was conducted in Tigray Regional State, located in the northern part of Ethiopia (Figure 1)
Al., 2018; Viste et al, 2013; Webb and Braun, 1990)
Drought characterization: The results indicate that the average drought intensity, the product of both duration and severity, varied from 0.59 at 12-month time scale to 0.77 at 3-month time scale

Summary

MATERIALS AND METHODS

Study area: This study was conducted in Tigray Regional State, located in the northern part of Ethiopia (Figure 1). The altitude of the study area varies from about 500 meters above sea level in the northeast to around 3800 meters above sea level in the southwest This marked variation in altitude governs the climatic conditions resulting in a distinct spatial distribution of temperature and rainfall in the area (Abraha, 2013; Tesfay, 2006). The gridded CRU TS 4.01 data are month-bymonth variations in climate over the period 1901 to 2017, provided, produced by CRU at the University of East Anglia (Harris and Jones, 2017). These datasets were chosen for their wider application in various studies and spatial and temporal coverage. For the non-random time series data correlation coefficient was used to further understand the strength and direction (increasing or decreasing) of the trend

AND DISCUSSION

Findings

Conclusion