The characterisation of rainfall in the arid and semi-arid regions of Ethiopia

Abstract

In order to plan effective agricultural and water resource projects, it is necessary to understand the spatial and temporal variability
of rainfall. Although it is one of the most drought-hit countries in the world, almost no study has ever been conducted in characterising the rainfall pattern of the arid and semi-arid regions of Ethiopia. In this study, rainfall data of the past 50 years was used to study the basic statistical characteristics of the rainfall of this region. Annual and monthly rainfall was fitted to the theoretical probability distributions and the best distributions describing the data at respective stations were determined. Probability of wet days and dry periods of different durations was determined. It has been found that both annual and monthly rainfall at different stations was described by different probability distributions. There is high variation of rainfall pattern among the stations. Heavier rainfall events are infrequent but they make up a significant percentage of the total rainfall. In arid and semi-arid regions where both the amount and frequency of rainfall occurrence is low, it is essential to take into account the unique rainfall characteristics in such regions.

Water SA Vol.32 (3) 2006: pp.429-436