Severity - Duration - Frequency (SDF) Analysis of drought for Abaya - Chama Basin, South Ethiopia

Abstract

One of the famous and universally applied drought index known as Palmer Drought Severity Index (PDSI) was used to examine the drought parameters of the basin. This method used precipitation, evapotranspiration, soil moisture recharge and soil moisture loss as an actual and potential values as input data. To study the drought situation of the basin, 34 years rainfall and mean temperature data were collected from 18 stations which located in side the basin and also the soil types derived from soil map was also collected from • Ministry of Agriculture, Ethiopia, t The analysis shows that PDSI can be positive (moisture surplus) or it can be negative (moisture stress or drought) condition. By using the result of PDSI values of each station, SDF graph of the basin were developed. Accordingly, the 5 year return periods of drought shows 8% of the basin was a drought duration less than 5 months, 74% of the basin was a drought duration of 5 to 6 months, 16% of the basin was a drought duration of 6 to 7 months and 2% of the basin was a drought duration of 7 to 8 months whereas a 10 year return periods shows 2% of the basin was a drought duration less than 9 months, 6% of the basin was a drought duration of 9 to 10 months and 92% of the basin was a drought duration of 10 to 17 months. Finally the severity, duration and frequency of occurrences of the drought were regionalized by interpolating the value of SDF at each station by help of Arc View GIS environment.