Rainfall variability and trends in the Borana zone of southern Ethiopia

This paper has examined the variability and trends of rainfall in the Borana zone, southern Ethiopia. Monthly rainfall data from 1981 to 2018 were obtained from the National Meteorological Agency (NMA) of Ethiopia. Mean, standard deviation and coefficient of variation were employed to analyze temporal variability. Mann-Kendall (MK) test and Sen's slope estimator (SEE) were used to determine trend and its magnitude, respectively. The inverse weighting distance (IDW) interpolation technique was employed to generate surface data and produce spatial rainfall maps. April and Belg were the wettest month and season, respectively. On an annual basis, Arero (741 mm) followed by Teltele (629 mm) were the wettest stations, whereas the Dillo station (285 mm) was the driest. Rainfall is highly variable on a monthly and seasonal basis than annual timescale. Meher rainfall has shown a significant rainfall increase (P-value <0.05) at most stations. A significant increase in annual rainfall was observed at Arero, Dehas, Dillo and Miyo. Spatially, rainfall decreases from the northeast and northwest parts of the Borana towards the southwest. The findings of this study can serve as a reference basis and provides useful information for policymakers to devise and implement better water management strategies in this water-scarce region.