Droughts in the United States

Droughts in the United States
Phoenix7777 · CC BY-SA 4.0 · source
Name	Droughts in the United States
Location	United States
Date	Various
Type	Environmental disaster
Fatalities	Variable
Damages	Variable

Droughts in the United States are recurrent, regionally variable episodes of below-normal precipitation and soil moisture that reduce water availability across parts of the United States. These events have shaped development in the Southwest United States, Central Plains, and California through interactions with agriculture, urbanization, and water infrastructure linked to agencies such as the United States Geological Survey, Bureau of Reclamation, and United States Department of Agriculture. Understanding droughts requires integrating paleoclimate records, modern observations, and socioeconomic data from institutions like the National Oceanic and Atmospheric Administration, National Aeronautics and Space Administration, and the National Centers for Environmental Prediction.

Overview and Definitions

Drought classification systems used in the United States include indices such as the Palmer Drought Severity Index, the Standardized Precipitation Index, and the Crop Moisture Index, developed by researchers affiliated with the National Weather Service, NOAA National Centers for Environmental Information, and academic programs at University of Arizona and Colorado State University. Operational designations by the U.S. Drought Monitor combine inputs from the National Drought Mitigation Center, the United States Department of Agriculture, and the National Oceanic and Atmospheric Administration to create weekly maps informing officials in jurisdictions such as California Governor's Office, Texas Commission on Environmental Quality, and Arizona Department of Water Resources. Legal declarations and emergency responses often invoke statutes like the Federal Emergency Management Agency authorities and state-level water rights administered under systems influenced by the Prior appropriation doctrine.

Historical Drought Events

Major historical events include the Dust Bowl of the 1930s, which devastated the Great Plains and prompted federal programs such as the Soil Conservation Service and New Deal initiatives under Franklin D. Roosevelt; the 1950s Southern Plains drought that affected Texas and Oklahoma and led to changes in Agricultural Adjustment Act-era support; the 1976–1977 California drought that influenced metropolitan water planning in Los Angeles and San Francisco; the 1988–1989 North American drought impacting the Midwest and prompting congressional action involving the United States Congress; and the 2011–2017 multi-year drought in the Western United States including sustained deficits in California, Nevada, and Colorado River storage that engaged the Bureau of Reclamation and interstate compacts such as the Colorado River Compact. Paleoclimate analyses using tree rings from the White Mountains (California) and Dendrochronology studies have identified medieval megadroughts contemporaneous with societies in the Ancestral Puebloans occupation of the Four Corners region.

Causes and Climatic Drivers

Primary drivers include variability in Pacific Ocean conditions such as El Niño–Southern Oscillation, sea surface temperature anomalies tied to the Pacific Decadal Oscillation, and teleconnections with the Atlantic Multidecadal Oscillation, all modulated by atmospheric circulation features like the jet stream (atmospheric). Anthropogenic warming linked to the concentration trajectory described by the Intergovernmental Panel on Climate Change increases evaporative demand and interacts with land-surface feedbacks documented by researchers at Princeton University, Stanford University, and the Massachusetts Institute of Technology. Land-use changes from expansion in regions such as the Central Valley (California) and irrigation practices studied by the United States Department of Agriculture alter soil moisture and groundwater dynamics monitored by the GRACE satellite mission and modeled in studies published by the National Academies of Sciences, Engineering, and Medicine.

Regional Impacts and Vulnerabilities

The Southwest United States faces chronic water scarcity in river basins like the Colorado River, affecting cities such as Las Vegas and Phoenix and tribal nations including the Navajo Nation; the Central Plains and Midwest are sensitive to agricultural production declines in Iowa, Nebraska, and Kansas that impact commodity markets tracked by the Chicago Board of Trade and policy responses in the United States Department of Agriculture. Coastal California combines urban demand in the San Francisco Bay Area and Los Angeles County with ecosystem stresses in the Sacramento–San Joaquin River Delta; the Southeast United States exhibits episodic drought linked to reservoir levels managed by agencies like the Tennessee Valley Authority and state water authorities in Georgia (U.S. state). Rural communities, tribal governments, and sectors reliant on hydroelectric generation at dams such as Hoover Dam exhibit high vulnerability when inflows decline.

Socioeconomic and Environmental Consequences

Droughts reduce crop yields for commodities like corn and soybeans in states including Iowa and Illinois, raise irrigation demand in the Central Valley (California), and strain municipal supply systems in metropolitan areas such as Los Angeles and Houston. Economic impacts ripple through regional labor markets and are quantified in analyses by the Congressional Budget Office and Federal Reserve Bank branches; public health outcomes and wildfire risk involve entities like the Centers for Disease Control and Prevention and United States Forest Service, which manages wildfire suppression in collaboration with state agencies like the California Department of Forestry and Fire Protection. Ecological consequences include reduced streamflow affecting species protected under the Endangered Species Act, altered wetland function in the Everglades, and salinity intrusion in estuaries such as the Chesapeake Bay.

Monitoring, Prediction, and Data Sources

Operational monitoring relies on remote sensing from satellites operated by NASA such as the Landsat program, gravimetric data from the GRACE satellite mission, and meteorological observations synthesized by the National Weather Service and NOAA National Centers for Environmental Information. Predictive tools incorporate seasonal forecasts from the Climate Prediction Center, hydrologic models from the Hydrologic Research Center, and decision-support systems developed at universities including University of Colorado Boulder and University of California, Davis. Data on water allocations and reservoir storage are published by agencies like the Bureau of Reclamation, the U.S. Army Corps of Engineers, and state water boards such as the California State Water Resources Control Board.

Mitigation, Adaptation, and Policy Responses

Responses include infrastructural measures such as reservoirs managed by the Bureau of Reclamation and U.S. Army Corps of Engineers, demand management programs in municipalities like San Diego and Austin, Texas, groundwater regulations exemplified by California Sustainable Groundwater Management Act, and market mechanisms including water banking and trading used in California Water Districts and interstate arrangements under the Colorado River Compact. Federal programs offering disaster assistance and conservation incentives involve the Federal Emergency Management Agency and Natural Resources Conservation Service, while research and long-term planning are supported by the National Science Foundation, Smithsonian Institution collaborations, and multi-state initiatives like the Western Governors' Association. Adaptation pathways emphasize diversified supply portfolios, improved irrigation efficiency promoted by the United States Department of Agriculture, ecosystem-based management advocated by conservation organizations such as The Nature Conservancy, and legal reforms addressing allocation among users and sovereign rights of Tribal nations.

Category:Natural disasters in the United States