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Hydrology Sub-Committee George Smith, Coordinator

The monitoring and forecasting of drought is directly related to the mission of the National Hydrologic Warning Council. Droughts are a type of hydrologic hazard that do not occur suddenly, but take a long period of time to develop. Generally speaking, droughts are caused by prolonged periods of little or no precipitation. In the eastern United States, this is usually a lack of rainfall. In the West, water supplies depend upon snowmelt from the mountains. Droughts can also occur due to the lack of groundwater in underground aquifers.

Usually there is no loss of life involved with droughts in the United States, but there are severe socioeconomic and environmental impacts during these events. On average, droughts are the most expensive hydrologic hazard, averaging between $6-8 billion annually (FEMA, 1995).

Monitoring the streamflow and water quality of rivers, rainfall amounts, air termperatures, soil moisture, and aquifer groundwater levels during droughts are extremely useful to water resources managers in times of drought. Many analytical tools are also available, such as the Standardized Precipitation Index, the Drought Monitor, and various drought indices are available.

Forecasting drought and drought warning is closely related to the prediction of certain atmospheric conditions, such as the El Nino-Southern Oscillation (ENSO). Climate models and ocean buoys help detect the beginnings of ENSO and can provide forecasts well in advance of the event. However, the dynamic nature of the atmosphere provides uncertainty to these forecasts.

For more information about drought, monitoring for drought, and how to mitigate against drought, please visit the National Drought Mitigation Center.


  • FEMA. 1995. National Mitigation Strategy; Partnerships for Building Safer Communities. Mitigation Directorate, p. 2. Federal Emergency Management Agency, Washington, D.C.
  • National Drought Mitigation Center (



  • Western Governor's Association & Western States Water Council workshop "Drought, Water, and Climate: Using today's Information and Designing Tomorrow's Services" will be held in Washington DC September 14-15, 2010. Visit for more information.

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