Monitoring Drought

Because there is no single definition for drought, its onset and termination are difficult to determine. We can, however, identify various indicators of drought, and tracking these indicators provides us with a crucial means of monitoring drought. Determining which indicators to use poses more difficulties for planners: should they rely on data collected for specific parameters (such as streamflow and snowpack), or should they select one or more indices, which incorporate and weigh various types of data in various combinations? Equally important in choosing these indicators is a consideration of the type or types of water shortage facing the planner—an index or parameters well suited to agricultural concerns are of limited use to urban planners.

How to Use this Section
If you are new to the concept of monitoring drought, “Drought Indices”, an NDMC white paper, will give you a good overview of the various kinds of drought indices and their uses. Two newer tools, the Standardized Precipitation Index and the Drought Monitor, are highlighted below. Use this section also to explore the many monitoring tools available on the web.

The Standardized Precipitation Index
The SPI is an index based on precipitation only. It can be used on a variety of time scales, which allows it to be useful for both short-term agricultural and long-term hydrological applications. You can download the SPI program and sample files here.

The Drought Monitor
A comprehensive drought monitoring effort between the USDA (JAWF/NRCS), NOAA/CPC (NCEP/NWS), NCDC (DOC/NOAA), and the National Drought Mitigation Center

Drought Impacts in the United States
A collection of impacts, links, and resource contacts for those areas of the United States affected by drought

Early Warning Systems for Drought Preparedness and Drought Management
The Proceedings of an Expert Group Meeting held in Lisbon, Portugal, in September 2000

Other Drought Monitoring Tools
A collection of links to sites providing information on other indices, forecasts, water supply conditions, and global climate