Drought Early Warning Systems

Droughts are usually classified in terms of their meteorological, hydrological, groundwater, agricultural or socioeconomic impacts. Forecasting challenges include the slow onset and wide spatial variability of events and the huge choice of possible criteria for issuing alerts. More recently, flash droughts have been recognized as another type of threat. Drought forecasting approaches range from simple empirical techniques through to integrated catchment models driven by rainfall and air temperature observations and forecasts. Drought indices are also widely used in early warning systems and drought response plans are an essential component. This chapter presents an introduction to these techniques together with examples of operational drought early warning systems such as the WMO Regional Climate Outlook Forums, the U.S. Drought Monitor and the Famine Early Warning Systems Network (FEWS NET).