Drought is a slow-moving natural hazard, so people may not realize that they're in the middle of one until it is long-established, with serious impacts. Urban dwellers, who live within very managed natural systems, may not have a way to notice dry conditions unless they deliberately seek data. Agricultural producers notice, but may tend to be optimistic about prospects for future rain, particularly given the choices presented by agricultural policy and financial necessity. Early warning systems can provide a "heads up" on dry conditions that would otherwise go unnoticed, allowing policymakers, water planners, and agricultural producers to make decisions based on the best available data.
Adopt an operational definition of drought.
Use triggers to link planned responses to drought, such as voluntary or mandatory water conservation, to the measured intensity of drought conditions.
A drought indicator looks at one or more variables, such as precipitation, to describe available water in soil or hydrologic systems. It may be a record of a single measurement, such as rainfall at a particular rain gauge.
A drought index is a type of indicator that mathematically combines one or more variables, such as precipitation and temperature, into a single map or assessment.
For more information: See our detailed Comparison of Drought Indices.
U.S. Drought Monitoring and Planning
At the national level, when policymakers are deciding whether to allocate millions or even billions of dollars in drought relief to farmers and ranchers, statistics that document long-term dry weather can help build the case for distributing emergency assistance. A drought index is a statistical analysis of climate data.
Analyses based on climatology, hydrology, and satellite-derived data are all valuable. So are local history and experience. At the state and national scales, economic crop loss data may be available. Monitoring should also be tailored according to past drought impacts and present vulnerability.
The NDMC maintains an extensive collection of drought monitoring tools and links to drought monitoring tools: U.S. Drought Monitoring Tools.
State Drought Monitoring and Planning
Many water and resource management decisions are state's responsibilities. State approaches to drought planning vary greatly based on how much they experience drought and strained water supplies, and on what part of the country they are in. Water law and land management functions differently in the western and eastern United States.
The NDMC maintains an extensive collection of state drought plans and resources. It includes local, regional and tribal plans and resources, accessible by drilling down from the state level.
Resource: See the 10-Step Planning Process, which has been adapted by many U.S. states as well as countries around the world.
Local, Regional and Tribal Drought Monitoring and Planning
Indian tribes, river basin commissions, water suppliers, planning commissions, municipalities, and individual farmers and ranchers all make decisions about land and water resources. The NDMC recommends that each governmental authority develop its own drought plan, addressing the specific issues that occur within its scope of authority. Note that water utilities' drought plans may be narrower in focus than the full range of issues experienced within a municipality. It is ideal if municipal drought plans are developed with awareness of larger regional or state plans.
Resource: See the Guide to Community Drought Preparedness.