ABSTRACT
This chapter presents the comparison of six drought indices: Standardized Precipitation Index, Standardized Precipitation and Evaporation index, Evapotranspiration Deficit Index, Soil Moisture Deficit Index, Aggregate Drought Index (ADI), and Standardized Runoff-discharge Index, and evaluates their performance with respect to identifying historic drought events in the Upper Blue Nile basin. The drought indices collectively characterize meteorological, agricultural, and hydrological drought types. The ADI is a multivariate drought index that aggregates the three types of drought through considering rainfall, evapotranspiration, and soil moisture. The comparison of the drought indices based on the drought characteristics such as percentage of drought months, maximum drought intensity, and drought duration was analyzed for the selected 16 stations that represent the majority of the study area. The agricultural drought indices showed a similar pattern with the meteorological drought indices of smaller time scales. The maximum duration of drought was also considered as another comparison criteria of drought indices for all time scales.
