A drought is defined as "a period of abnormally dry weather sufficiently prolonged for the lack of water to cause serious hydrologic imbalance in the affected area." - Glossary of Meteorology (1959).
If a weather pattern that results in a precipitation deficit lasts for a few weeks or months, it is considered short-term drought. If the pattern and precipitation deficits last for more than six months, it is typically considered long-term or prolonged drought.
From 2011 through 2020, the United States experienced nine droughts, each causing at least $1 billion in damages.
As droughts persist for longer periods of time and expand into more regions, impacts to various critical infrastructure will increase:
- Water supply: During droughts, communities may have limited access to water for household use, including drinking, cooking, cleaning, and watering plants, as well as for agriculture, transportation, and power generation. Droughts may lead to higher water costs, rationing, or even the decimation of important water sources like wells, as a drought did in a rural California community in 2021.
- Agriculture: Droughts affect livestock and crops, including corn, soybeans, and wheat. At the height of the 2012 drought, the U.S. Department of Agriculture declared a natural disaster over 2,245 counties, 71 percent of the United States. Globally, drought struck several major breadbasket regions simultaneously in 2012, adding to food price instability. In countries already facing food insecurity, cost spikes can lead to social unrest, migration, and famine.
- Transportation: Hot temperatures resulting in increased evaporation during a time with decreased rainfall can result in draft and tow restrictions as water levels in the river system become too low to safely operate. About 60% of all US grain exports move down the Mississippi River to ports in Louisiana, while fertilizer, metals, crude oil and other products move upriver. Due to low flowing river waters from an overall decrease in rainfall across the region, the barge transport reported a delay of more than 2,250 vessels the second week of October 2022. The US Army Corps of Engineers has dredged to make water levels deeper. This has raised costs and made US cargoes more expensive when food inflation is already at its highest level in four decades due to drought impacts across the agriculture sector. Drought is also often accompanied by extreme heat, which can buckle roadways, render airport runways unsafe, and warp public transit cables. Drought-fueled wildfires also have repercussions for travel by closing roadways and railroads and grounding planes when smoke is thick.
- Energy: Droughts can raise concerns about the reliability of electricity production from plants that require cooling water to maintain safe operations. Hydroelectric power may also become unavailable during droughts. When heat waves coincide with droughts, electricity demands can grow, compounding stress on the grid.
- Public Health: Reduced flows in rivers and streams can concentrate pollutants, threatening the quality of water used for drinking and recreation. Also, drought-fueled wildfires can expose nearby communities to smoke and pollutants, which can exacerbate chronic respiratory illnesses.
Impacts Upon Critical Infrastructure
Droughts can impact critical infrastructure sectors such as transportation, energy and water that millions of Americans depend upon.
- Drought can cause overpulling of aquifers resulting in subsidence (ground sinking, potholes, large surface cracks) which can damage all parts of the transportation sector, building foundations, supporting infrastructure, and structural integrity of poles/towers.
- Less surface water availability may result in a decreased availability of cooling capability for electricity-heavy facilities like datacenters, nuclear plants, and other powerplants in the energy sector.
- A threat to water provisions may cause local resource hording or theft through resource security. Theft from key facilities like fire stations, reservoirs, water towers, hospitals, and farms/natural sources have been reported in previous longer-term droughts.
- Drought impacts can reduce water provision to defense industrial bases, can degrade water quality to healthcare sector facilities, can reduce operations for government facilities, and can halt critical manufacturing and could impact the chemical sector as water is a key component in many mixtures and dilutions.
- Drought can lead to low-flowing river systems and warmer surface waters more conducive to algal blooms potentially damaging dams and locks, reducing water transportation with cascading impacts to the supply chain, and reduced hydroelectric capabilities across multiple regions.
- Drought can result in higher costs for feed/hay for livestock, smaller crop yields, and marine loss from overheated waters resulting in higher grocery costs nationally and a direct impact to the workforce and homelife security.
- Increased demand with minimal capabilities to fulfill supply can result in uneven distribution of wealth across farming communities and could result in financial instability spreading from local to regional and influencing national pricing, policy.
CISA’s Role in Increasing Drought Resilience
CISA is a member of The National Drought Resilience Partnership, which leverages technical and financial Federal resources, strengthens communication, and fosters collaboration among its members to productively support State, tribal, and local efforts to build, protect, and sustain drought resilience capacity at regional and basin scales. CISA remains a principal partner within the council for reporting to the Water Subcabinet.
Look up drought conditions by zip code, read about past droughts and discover the science behind droughts in this all-in-one portal.
The Monitor synthesizes data from academic and federal scientists into a weekly map indicating levels of dryness around the country.
The Palmer Drought Severity Index (PDSI), developed in 1965 by the National Weather Service, is the most commonly-used drought monitor.