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| 2020s southwestern North America megadrought | |
|---|---|
| Name | 2020s southwestern North America megadrought |
| Location | Southwestern United States, Northern Mexico |
| Period | 2020s |
| Type | Megadrought |
| Causes | Climate change, La Niña, Pacific Decadal Oscillation |
2020s southwestern North America megadrought is a prolonged period of extreme aridity affecting parts of the Southwestern United States and Northern Mexico during the 2020s. The event has been characterized by multi-year precipitation deficits, record heat, and widespread hydrological stress across major river basins, reservoirs, and aquifers. It has drawn attention from agencies and institutions such as the National Oceanic and Atmospheric Administration, United States Geological Survey, NASA, Mexican National Institute of Statistics and Geography, and academic centers including University of Arizona, Stanford University, University of California, Berkeley, and University of New Mexico.
Scientists link the megadrought to persistent modes of ocean–atmosphere variability and long-term warming trends observed by Intergovernmental Panel on Climate Change, World Meteorological Organization, National Aeronautics and Space Administration, and European Centre for Medium-Range Weather Forecasts. Contributions have been attributed to recurrent La Niña episodes, shifts in the Pacific Decadal Oscillation, and altered sea surface temperatures in the Northeast Pacific Ocean and Tropical Pacific Ocean. Human-driven greenhouse gas emissions cited by IPCC Sixth Assessment Report have increased evaporative demand across the Colorado River Basin, Rio Grande Basin, and the Baja California Peninsula. Paleoenvironmental comparisons using tree-ring records from researchers at Tree-Ring Laboratory, University of Arizona, Lamont–Doherty Earth Observatory, and University of Nevada, Reno indicate that the 2020s event aligns with previous megadroughts recorded during the periods examined by Edward Cook and Richard Seager.
The drought encompassed large parts of the Four Corners region, California, Nevada, Utah, Arizona, New Mexico, Texas, and northern states of Sonora and Baja California. Key water systems affected include the Colorado River, Lake Mead, Lake Powell, the Gila River, the Rio Grande, and the Mojave Desert aquifers monitored by US Bureau of Reclamation, Arizona Department of Water Resources, California Department of Water Resources, Texas Water Development Board, and Comisión Nacional del Agua. Onset began in the late 2010s and intensified through 2020–2024 with record low snowpacks recorded by Sierra Nevada stations, continuing into subsequent years with episodic relief during altered atmospheric patterns documented by NOAA Climate Prediction Center and the National Integrated Drought Information System.
Atmospheric observations from NOAA National Centers for Environmental Information, NASA Goddard Institute for Space Studies, and Potsdam Institute for Climate Impact Research show anomalous warmth coincident with precipitation deficits across the region. Snow water equivalent declines in the Sierra Nevada, Wasatch Range, San Juan Mountains, and San Francisco Peaks reduced spring runoff to the Central Valley Project, Los Angeles Aqueduct, and municipal supplies for cities such as Los Angeles, Phoenix, Las Vegas, Albuquerque, and Tucson. Reservoirs including Lake Mead and Lake Powell reached historic lows, triggering operational adjustments by the Upper Colorado River Commission, Lower Colorado River Basin states, and emergency declarations by state governors including those of California, Arizona, Nevada, and New Mexico. Groundwater extraction increased in rural basins monitored by USGS Groundwater Resources Program, accelerating aquifer depletion and land subsidence observed by InSAR analyses conducted by Jet Propulsion Laboratory and California Department of Water Resources.
Vegetation stress and tree mortality surged in forests managed by U.S. Forest Service, National Park Service, and the Bureau of Land Management, with widespread die-off among Ponderosa pine stands in the Kaibab National Forest and bark beetle outbreaks documented by entomologists at Colorado State University and University of Montana. Wildfire seasons intensified, affecting protected areas such as Joshua Tree National Park, Grand Canyon National Park, and Sequoia National Park, and attracting federal coordination through the Federal Emergency Management Agency and National Interagency Fire Center. Agriculture in the Imperial Valley, Central Valley (California), and irrigated zones in Sonora faced fallowed fields, crop losses for alfalfa and cotton, and shifts reported by United States Department of Agriculture, California Farm Bureau Federation, and Mexican agricultural agencies. Aquatic ecosystems in the Colorado River Delta and Gila River suffered habitat contraction affecting species monitored by U.S. Fish and Wildlife Service, International Union for Conservation of Nature, and local Indigenous communities such as the Tohono O'odham Nation and Pascua Yaqui Tribe.
Municipal water restrictions affected metropolitan regions including Los Angeles, San Diego, Phoenix Metropolitan Area, Las Vegas Valley, El Paso, and Ciudad Juárez. Water-sharing agreements among Seven Basin States and agencies like the Bureau of Reclamation and Colorado River Board of California were renegotiated, invoking provisions under laws such as the Colorado River Compact and prompting involvement from state legislatures and governors including those of California, Arizona, Nevada, Utah, and Colorado. Economic impacts were reported by Federal Reserve Bank of San Francisco, U.S. Chamber of Commerce, International Monetary Fund analyses, and local chambers of commerce, with losses in agriculture, recreation, and hydropower revenues affecting utilities like Los Angeles Department of Water and Power and Salt River Project. Public health effects, exacerbated by extreme heat events in coordination with studies from Centers for Disease Control and Prevention and Harvard T.H. Chan School of Public Health, increased heat-related morbidity among vulnerable populations including residents of Native American reservations such as the Navajo Nation.
Responses included short-term conservation measures enacted by municipal agencies like Metropolitan Water District of Southern California and Las Vegas Valley Water District, regional planning by entities such as the Colorado River Board, and federal actions from the Bureau of Reclamation and U.S. Department of the Interior. Investments in infrastructure, desalination projects advocated by San Diego County Water Authority and Orange County Water District, and groundwater recharge initiatives involving Central Arizona Project and Groundwater Recharge Districts were pursued. Policy responses involved legislation at the California State Legislature, Arizona State Legislature, and bilateral negotiations coordinated by U.S.–Mexico High-Level Economic Dialogue with participation from Secretaría de Medio Ambiente y Recursos Naturales and Comisión Nacional del Agua. Non-governmental and philanthropic actors including The Nature Conservancy, Sierra Club, Natural Resources Defense Council, and foundations such as the Gordon and Betty Moore Foundation funded restoration, water efficiency, and research programs.
Research led by institutions like University of Colorado Boulder, Scripps Institution of Oceanography, Yale University, Princeton University, Massachusetts Institute of Technology, and Carnegie Institution for Science has focused on attribution studies, paleoclimatology, and water resources modeling using tools from NOAA, USGS, and NASA. Debates have centered on the relative roles of natural variability versus anthropogenic forcing highlighted in discussions at meetings of the American Geophysical Union and American Meteorological Society. Controversies also involve water rights adjudication adjudicated in courts such as the U.S. District Court for the District of Arizona and interstate litigation among Colorado River Basin states, the ethics of groundwater pumping affecting Indigenous water sovereignty for tribes including the Hopi Tribe and Ute Mountain Ute Tribe, and proposed engineering solutions debated in hearings before the United States Congress and the Mexican Congress.
Category:Droughts in the United States Category:2020s in the United States Category:Environmental issues in Mexico