Article

Rainfall Variability and Trend Analysis in Case of Dijo River Watershed Central Rift Valley Basin of Ethiopia

Abstract

Rainfall is the most important variable climate element that controls and regulates agricultural operations and crop production worldwide. This study sought to evaluate rainfall variability from monthly to decadal levels, as well as its trend, in the Dijo River Watershed from 1985 to 2018. Statistical tools like; mean, SD, CV, PCI and SRAI methods were used to identify the degree of rainfall variability, distribution, frequency of drought intensity and its occurrence. Mann-Kendall's and Sen.’s slope estimator statistical test was used to compute trend detection. The result of the study shows that statically significant decreasing and increasing rainfall trend at 5% and 1% level of significance during beginning of bega season. The seasonal rainfall contributions to the annual rainfall totals varied largely over the study area. The variation of PCI values ranges from uniform during kiremt season to strongly irregular distribution at bega season. The finding also revealed that the probability of negative rainfall anomalies was increased in recent years due to rapid population growth and expansion of agriculture activities in study watershed. Due to monthly, In light of the yearly and internal annual rainfall variations and trends over the study watershed, it was recommended that an adaptation strategy be adopted to mitigate the impact of climate change.

Keywords: climate change, climate variability, mann-kendall, trend.