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| North American droughts | |
|---|---|
| Name | North American droughts |
| Date | Various |
| Location | North America |
North American droughts are intermittent episodes of prolonged below-average precipitation and soil moisture affecting large portions of the United States, Canada, Mexico, and adjacent territories. These events have recurred from pre-Columbian times through the Dust Bowl of the 1930s to 21st-century episodes such as the 2011–2017 southwestern drought and the 2020s Western United States drought. Impacts have reached into sectors and institutions including United States Department of Agriculture, National Oceanic and Atmospheric Administration, Environment and Climate Change Canada, and Comisión Nacional del Agua.
Droughts are classified using indices such as the Palmer Drought Severity Index, the Standardized Precipitation Index, and the Soil Moisture Active Passive satellite-derived metrics, applied across basins like the Colorado River and the Mackenzie River. Definitions vary by community: meteorological droughts (precipitation deficits), agricultural droughts (soil moisture deficits impacting crops like corn and soybean), hydrological droughts (streamflow reductions in systems such as the Mississippi River), and socioeconomic droughts (water allocation conflicts in jurisdictions like California and Texas). Key observatories and agencies include National Aeronautics and Space Administration, US Geological Survey, Purdue University research centers, and regional water authorities such as the Bureau of Reclamation.
Historic episodes are documented through paleoclimate proxies and archival records used by institutions like the Smithsonian Institution and the American Geophysical Union. Major 20th-century events include the Dust Bowl (1930s), which affected the Great Plains and led to migrations to places like California and policy responses under the New Deal; the 1950s drought that stressed the Ogallala Aquifer and prompted projects by the Tennessee Valley Authority; and the late-20th and early-21st-century southwestern droughts that strained the Colorado River Compact and reservoirs such as Lake Mead and Lake Powell. Paleodroughts reconstructed from tree rings implicate megadroughts during medieval periods, contemporaneous with societies including the Ancestral Puebloans and the Mississippian culture.
Droughts arise from variability in phenomena including the El Niño–Southern Oscillation, Pacific Decadal Oscillation, and North Atlantic Oscillation, which modulate storm tracks affecting regions from the Pacific Northwest to Yucatan Peninsula. Anthropogenic forcing linked to global warming alters evapotranspiration and snowpack dynamics in ranges such as the Rocky Mountains and the Sierra Nevada, shifting runoff timing into channels managed by entities like the Metropolitan Water District of Southern California. Teleconnections with the Arctic Oscillation and tropical modes like the Atlantic Multidecadal Oscillation further influence precipitation patterns over basins governed by compacts among states like Arizona, California, and Nevada.
Agricultural impacts have affected commodity systems involving Kansas wheat, Iowa corn, and California almond orchards, interacting with institutions such as the Chicago Board of Trade and the Food and Agriculture Organization. Water supply shortages have led to restrictions in metropolitan areas served by systems like the Central Arizona Project and the Los Angeles Aqueduct, and to stress on transboundary resources shared by United States and Mexico under agreements like the 1944 United States–Mexico Treaty. Ecosystems from the Boreal forest to the Sonoran Desert exhibit tree mortality (e.g., Pinus ponderosa die-off) and shifts in wildfire regimes affecting United States Forest Service and Parks Canada management. Fisheries in river systems such as the Columbia River and wetlands like the Everglades have experienced altered hydrology impacting species managed under frameworks like the Endangered Species Act.
Droughts influence commodity prices on platforms such as the New York Mercantile Exchange and drive migration patterns documented in studies by University of California, Berkeley and Harvard University. Public health effects include heat stress exacerbations noted by Centers for Disease Control and Prevention, respiratory ailments from dust events linked to Dust Bowl conditions, and vector-borne disease shifts monitored by agencies like Public Health Agency of Canada. Water allocation disputes have involved courts such as the Supreme Court of the United States and interstate compacts, and have implications for indigenous nations including the Navajo Nation and the First Nations of Canada.
Monitoring networks combine in situ gauges from the National Weather Service and the Hydrometeorological Prediction Center with remote sensing from Landsat, MODIS, and missions like GRACE to assess groundwater depletion. Predictive skill relies on seasonal forecasts from NOAA Climate Prediction Center and dynamical models developed at centers like National Center for Atmospheric Research and European Centre for Medium-Range Weather Forecasts; ensemble products inform stakeholders including the Western Governors' Association and municipal agencies such as the City of Phoenix. Early warning systems integrate indices used by the United Nations Office for Disaster Risk Reduction and regional drought task forces.
Responses span supply-side engineering—reservoirs like Hoover Dam and interbasin transfers—and demand-side measures: water markets in Colorado River Basin states, tiered pricing in cities like Los Angeles, and conservation programs administered by the USDA Natural Resources Conservation Service. Policy instruments include interstate compacts like the Colorado River Compact, binational accords such as the Minute 319 agreement, and state laws exemplified by legislation in California (e.g., regional water boards). Adaptation strategies emphasize soil health and crop diversification studied at institutions like Iowa State University and University of Arizona, ecosystem-based approaches advocated by The Nature Conservancy and community resilience planning led by organizations such as Red Cross chapters. Research agendas are coordinated through entities like the National Academies of Sciences, Engineering, and Medicine and international collaborations under the Intergovernmental Panel on Climate Change.
Category:Natural disasters in North America