ABSTRACT
There are many indicators that are used to identify drought episodes. A drought index assimilates climatic data and other water resources indicators and is typically a single number, which is very useful for decision-making. They are related to the data of precipitation, snow, river flows, and water supply indicators. In general, a single index to characterize the drought is not used in a study area. Most water supply planners find it useful to consult two or more indexes before making a decision. None of the indices can be considered superior to another, and their use is dependent on the data available in the study area and on the assessment of the impacts on flows, soil moisture, forest growth, and crop yield. In this chapter, some of the drought indices mostly used in the water resources planning and management are described.
