Temporal rainfall variability and drought characterization in Cheleka Watershed, Awash River Basin, Ethiopia

Abstract

Study region: Cheleka Watershed, lower Awash River Basin, Ethiopia. Study focus: The lower part of Awash River (Cheleka Watershed) with an area of 1744.48 km2 has limited rainfall temporal variability and drought incidence data. So, the study analyzed the temporal rainfall variability and drought incidence from five meteorological station starting from1988 up to 2017. Coefficient of variation, precipitation concentration index, mean and standard deviation were computed to analysis the temporal variations of rainfall; frequency and severity of droughts were characterized through rainfall anomalies indexes (RAI) and standardized precipitation indexes (SPI). New hydrological insights for the region: The study found that, mean annual rainfall with a range value of 908.90 mm - 1181.48 mm in Batie and Majetie station respectively. Kiremt rainfall total with the highest coefficient of variation (22.93–29.12%) next to Belg rainfall total (39.31–52.43%) and the lowest variations of annual rainfall total (15–22.59%). Frequency of drought in 12 month’s interval indicates severely dry droughts, most frequently next to moderately dry drought. The maximum frequency for severely dry (8.61%) and moderately dry (11.39%) drought were occurred in Kemisse station. The longest duration and the highest magnitude drought were occurred in Kombolcha station next to Kemisse. As recommendation, since, this study was focused only temporal rainfall variability and drought characteristic, it is better that, future research will be conducted to evaluate the spatial rainfall variability and hydrological drought severity nature and its impact on socio-economic and human well-beings in the area.

Keywords

• Cheleka watershed
• Rainfall variability
• Drought
• PCI and SPI