North American megadrought (2020s)

North American megadrought (2020s)
Name	North American megadrought (2020s)
Type	Drought
Region	Western United States; Mexico; Canada (southwest)
Start	2020
Status	Ongoing (2020s)
Causes	Prolonged precipitation deficits, anomalous sea surface temperatures, anthropogenic warming

Contents

North American megadrought (2020s) The North American megadrought (2020s) is a prolonged, large-scale drought affecting the Western United States, northern Mexico, and parts of southwestern Canada beginning in 2020 and continuing through the 2020s. It involves sustained precipitation deficits, elevated temperatures, and hydrological stress across major river basins including the Colorado River, Rio Grande, and Sacramento River, with wide-ranging impacts on agriculture in the Central Valley (California), urban water supplies for metropolitan areas such as Los Angeles, Phoenix, and Las Vegas, and on ecosystems from the Sierra Nevada to the Sonoran Desert. Scientists link the event to interactions among the Pacific Decadal Oscillation, El Niño–Southern Oscillation, and long-term anthropogenic climate change documented by institutions like the National Oceanic and Atmospheric Administration and the Intergovernmental Panel on Climate Change.

Background and climate drivers

The megadrought arises from multi-year precipitation deficits tied to variability in the Pacific Ocean and Atlantic Ocean coupled with increased evaporation from higher temperatures recorded by the National Aeronautics and Space Administration and NOAA. Drivers include a prolonged positive phase of the Pacific Decadal Oscillation and episodes of La Niña during the early 2020s that shifted storm tracks away from the North American West Coast, affecting regions from the Cascade Range to the Baja California Peninsula. Anthropogenic warming attributed to greenhouse gas emissions overseen by initiatives like the United Nations Framework Convention on Climate Change has increased vapor pressure deficit and soil moisture depletion observed by the U.S. Geological Survey, amplifying drought severity in watersheds such as the Colorado River Basin, Upper Rio Grande, and the Klamath Basin.

The event intensified after successive dry years from 2012–2019 and emerged as a megadrought in 2020 as recorded in paleoclimate analyses from the National Center for Atmospheric Research and dendrochronology studies at the Smithsonian Institution and Lamont–Doherty Earth Observatory. Key milestones include critical low reservoir elevations at Lake Mead and Lake Powell, emergency declarations in states such as California, Arizona, and New Mexico, and coordinated river management actions by the U.S. Bureau of Reclamation and the International Boundary and Water Commission. Severity metrics—precipitation anomalies, soil moisture indices, snowpack deficits in the Rocky Mountains, and streamflow declines in the Columbia River and Sacramento–San Joaquin River Delta—were monitored by agencies including the National Drought Mitigation Center and the U.S. Department of Agriculture.

The megadrought has constrained irrigation in the Central Valley (California), reduced allocations from the Central Arizona Project, and stressed ranching in the Great Basin and Chihuahuan Desert. Hydropower generation at facilities operated by Bureau of Reclamation and California Independent System Operator declined with lower reservoir levels at Shasta Lake and Folsom Lake. Urban suppliers like the Metropolitan Water District of Southern California and Salt River Project instituted conservation mandates, while transboundary water management with Mexico involved the International Boundary and Water Commission. Ecosystems suffered from tree mortality in the Sierra Nevada and Grand Canyon regions, altered fire regimes leading to megafires such as the Dixie Fire and Caldor Fire, and declines in aquatic species including native salmon in the Sacramento River and Colorado pikeminnow in the Colorado River Basin.

Economic impacts include lost crop yields for commodities traded on markets like the Chicago Board of Trade and supply-chain effects for processors and exporters in ports including the Port of Los Angeles. Rural communities in Central Valley (California) counties and tribal nations such as the Navajo Nation experienced groundwater over-extraction and well failures monitored by the U.S. Environmental Protection Agency. Tourism and recreation revenues declined around national parks managed by the National Park Service including Grand Canyon National Park and Yosemite National Park. Insurance and emergency management burdens affected state budgets of California, Arizona, and Nevada, while federal responses involved the Federal Emergency Management Agency and congressional appropriations.

Responses combined short-term emergency measures and long-term reforms: reservoir operations revised by the U.S. Bureau of Reclamation, interstate compacts like the Colorado River Compact renegotiations, demand-management programs by utilities such as Denver Water and conservation campaigns led by NGOs including the Nature Conservancy and Environmental Defense Fund. Agricultural adaptations included crop switching by producers represented in the California Farm Bureau Federation and investments in irrigation efficiency promoted by the Natural Resources Conservation Service. Urban policy actions involved water reuse projects, desalination proposals debated in San Diego County and Orange County, and water markets tested in states like Texas. International cooperation with Mexico addressed binational allocations under treaties administered by the International Boundary and Water Commission.

Research institutions—University of Arizona, Stanford University, University of California, Davis, Colorado State University, and University of Colorado Boulder—have published analyses linking drought severity to anthropogenic forcing in journals such as Science, Nature, and Geophysical Research Letters. Climate models from the Coupled Model Intercomparison Project ensembles project increased frequency of extreme drought under higher atmospheric carbon dioxide scenarios evaluated by the IPCC. Paleoclimate reconstructions using tree rings from the Laboratory of Tree-Ring Research and sediment cores from the Scripps Institution of Oceanography contextualize the 2020s drought versus medieval megadroughts. Ongoing monitoring by NOAA, USGS, and the National Integrated Drought Information System informs adaptation planning, while uncertainty remains about multi-decadal precipitation patterns linked to the Pacific Decadal Oscillation and potential shifts after El Niño events.

Category:2020s droughts Category:Climate change in the United States Category:Environmental disasters in North America