Trend Analysis of Rainfall Data in Wolaita Zone, Southern Regional State of Ethiopia
The aim of this study was to investigate the monthly, seasonal and annual rainfall variability in Wolaita Zone, Ethiopia. Standard statistical methods were employed to reveal the rainfall departure from the long time mean and its trend was presented using linear regression equations and graphical methods. The result shows the linear trend lines of the monthly rainfall shows decreasing trend in December, January, February and March and increasing trend for other months and annual rainfall data. The p-value computed for the monthly and annual rainfall data shows that, it is greater than significant level α=0.05, so that the null hypothesis, H0: that, there is no trend in data, is failed to be rejected. This reveals that there is no statistically significant trend in the data describing the monthly and annual rainfall in Woliata zone. Also for seasonal rainfall data, the linear regression analysis shows decreasing trend in Belg (FMAM) whereas an increasing trend has been observed for Kiremt (JJAS) and Bega (ONDJ) seasons.
Keywords - Rainfall Variability, Season, Regression, Trend Analysis, Anomaly, ICTZ, El Nino, La Nina