Abstract

Drought is a period of abnormally dry weather sufficiently prolonged because of a lack of precipitation that causes a serious hydrological imbalance and has connotations of a moisture deficiency with respect to water use requirements. The main objective of this research is to find out if Lake Hawassa sub basin is facing drought conditions. Accordingly, a number of objectives were accomplished like analysis of drought occurrence, trends of drought and delineating regions with high vulnerability to drought hazards. In this study, three temporal drought indices (Standardised Precipitation Index, Reconnaissance Drought Index and Stream flow Drought Index) were used to assess drought using metrological data and stream flow data. DrinC software is used for the analysis of Standardised Precipitation Index, Reconnaissance Drought Index and Stream flow Drought Index. Mann-Kendall test have been used together with the Sen’s Slope Estimator for the determination of drought trend and slope magnitude. Based on this research, Standardised Precipitation Index shows the drought during 1993 is the highest drought (6.87) with duration of four months, Reconnaissance Drought Index shows drought during 2015 is the highest drought (9.32) with duration of seven months and Stream flow Drought Index shows drought during 1982 is the highest drought (20.45) with duration of eleven months. The three indices show a high drought occurrence even if the time of occurrence is different. They also indicate an increasing drought trend within the data years. The results obtained from this study show that Lake Hawassa sub basin is facing drought conditions. Furthermore, it was concluded that the combination of various indices offer better understanding of drought conditions.

Keywords: DrinC; Drought; Lake Hawassa Sub-basin