Evaluating Variability and Characterization of Seasonal Rainfall Over East Shewa Zone, Oromia Region, Ethiopia

The objective of the research paper was classified as three main points. The first was to determine the seasonal and annual rainfall distribution of the zone. The second and the third was to evaluating seasonal rainfall variability and characterizing the seasonal rainfall of east Shewa zone in terms of onset and cessation date. Coefficient of Variation, Precipitation Concentration Index and Standardized Anomaly Index was the indicators used to assess the variability of seasonal rainfall of the zone for both main and second rainy season. Climatologically the zone received high amount of rainfall during June to September with peak value in July ranging from 300 to 660 averagely and during Belg with being peak in month of April with mean seasonal rainfall amount of 125 to 300. Bega is the dry period for the East Shewa zone as annual rainfall cycle result shown from the data of the year 1981 to 2020. Additionally 550 to 1060 mean annual rainfall observed during the study period. The result of coefficient of variation indicated that during the main rainy season its values ranged from 20 to 35% while from 30 to 50% during the second rainy season. It also indicated that high rainfall variability observed over Rift valley areas. The result stated that most parts of the zone are under moderate precipitation concentration during Kiremt and mostly irregular in the second rainy season. Standardized anomaly indicated that dry season dominated during second rainy period than the main rainy period. Characterization and identified variability of seasonal rainfall was important especially for rain-fed agriculture and hydrological advisory at zone level to support community.