Spatio-Temporal Variability and Trends of Annual and Seasonal Rainfall in Wolaita Zone, Ethiopia

This paper examined the spatiotemporal variability and trends of rainfall in the Wolaita Zone, Ethiopia. Rainfall data from fifteen stations from 1991 to 2020 is included, as well as data from important stations with longer observation periods. The variability of rainfall at the annual and seasonal scales was analyzed by using the coefficient of variation (CV) and standardized rainfall anomalies (SRA) over the study area. Mann-Kendall test was used to determine trend and Sen’s slope estimator was used to determine magnitude of the trend. Rainfall was highly variable during Belg season. The Belg season is the second rainy season, which received from 309.3 mm to 694.5 mm. Rainfall was moderately variable during the Kiremt season. The Kiremt season is the main rainy season, which received from 379.5 mm to 752.8 mm. Rainfall is less variable during annual times. At the annual time, rainfall was recorded from 910.3 mm to 1465.9 mm. At the annual and Kiremt time, almost all stations show increases in trend when P values < 0.005. On the other hand, at the Belg season, almost all stations show decreases in trends when P values < 0.005. The spatial distribution of rainfall is increasing in the highland area while decreasing in the lowland area of the Wolaita zone. The studying of rainfall variability and trend at temporal and spatial scales is hence useful for communities, local-level actors, and decision-makers for planning activities and devising appropriate adaptive strategies as well as to take informed decisions.