Characteristics of Seasonal Rainfall and its Distribution Over Bale Highland, Southeastern Ethiopia

Abstract

Agricultural productivity heavily depends on onset and cessation of rainfall and Length of Growing Period (LGP). Determining these variables is useful for early warning and preparedness. Therefore, the objective of this study was to show the onset, cessation and LGP of the seasons over Bale Highlands. Bale Highland is characterized by bi-modal rainfall types. In order to find Onset, Cessation and LGP of both Belg and Kiremt seasons, 30 years of rainfall data for periods of (1985 to 2014) in daily format from NMA (National Metrological Agency) Bale robe branch directorate was used. Additionally, for this study, 12 meteorological stations in the Bale Highlands were used. The study shows that there is high variability of onset and cessation in Belg season than kiremt season. The mean onset and mean cessation of Belg season over Bale Highland is March 28 and June 10 with mean standard deviation of 19 days, respectively. On the other hand, in kiremt season, mean onset and mean cessation were July 12 and October 31 with mean standard deviation of 16 and 12 days, respectively. During the major growing season (Kiremt) the mean LGP is 110 days with mean standard deviation of 19 days and for Belg season the mean LGP is 73 days with mean standard deviation of 26 days. The short in LGP and the variation of onset and cessation of the seasons will be considered by the concerned body to aware the local community on the onset and cessation as well as Length of growing period for both seasons. The result found more likely lead the traditional rain-fed agricultural practice in both seasons to shift to irrigation system.