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.

Characterisation of rainfall at a semi-arid ecotope in the Limpopo Province (South Africa) and its implications for sustainable crop production

“…Probability distributions are widely used in understanding the rainfall pattern and computation of probabilities (Abdullah and Al-Mazroui, 1998) and it is believed that events follow particular types of distributions (Tilahun, 2006). The normal distribution is one of the most important and widely used in rainfall analysis (Kwaku and Duke, 2007).…”

The Nature of Rainfall at a Typical Semi-Arid Tropical Ecotope in Southern Africa and Options for Sustainable Crop Production

“…In addition, the results also suggested that there is no constant best distribution function for rainfall distribution for all the months at an ecotope. In a similar study in Ethiopia, Tilahun (2006) found that most of the monthly rainfall data sets were best described by the lognormal distribution while annual rainfall distribution patterns fitted either the Weibull or the Gumbel or the Gamma distribution models. Table 3.…”

“…This was done partly to reduce the volume of data in subsequent analyses. The approaches used in data analysis were similar to those used by Belachew (2002) and Tilahun (2006).…”

“…The observed distributions were fitted to theoretical probability distributions by comparing the frequencies (Tilahun, 2006). Data normality was tested using www.intechopen.com skewness and kurtosis coefficients and probability distributions were evaluated with the aid of probability plots and curve fitting using Minitab 14 statistical software (Minitab Inc., 2004) ).…”

Participatory Planning of Appropriate Rainwater Harvesting and Management Techniques in the Central Rift Valley Dry Lands of Ethiopia

“…The annual rainfall variability and the non-productive loss of rainfall through soil evaporation and surface runoff are more limiting factors than the total annual amount in the CRV of Ethiopia Tilahun, 2006). Therefore, the objective of this study was to develop appropriate RWHM technologies in the CRV of Ethiopia through a participatory process.…”