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| 1983–1985 California drought | |
|---|---|
| Name | 1983–1985 California drought |
| Duration | 1983–1985 |
| Location | California |
| Severity | Severe |
| Causes | El Niño–Southern Oscillation, Pacific Decadal Oscillation |
| Impacts | Reduced Sierra Nevada snowpack, low Sacramento River and San Joaquin River flows, agricultural losses |
1983–1985 California drought was a prolonged hydrological drought affecting California during 1983–1985 that reduced runoff, depleted reservoirs, and stressed irrigation in the Central Valley, the Los Angeles Basin, and the San Francisco Bay Area. The event overlapped with regional climate fluctuations such as the El Niño–Southern Oscillation and the Pacific Decadal Oscillation and interacted with water demands from California State Water Project, Central Valley Project, and municipal suppliers like the Metropolitan Water District of Southern California. Impacts were felt across sectors including agriculture in the Sacramento Valley, hydroelectric generation at Shasta Dam, and urban supply in San Diego.
Preceding winter precipitation deficits followed patterns tied to El Niño–Southern Oscillation variability and an anomalous phase of the Pacific Decadal Oscillation, which influenced storm tracks across the Gulf of Alaska and the North Pacific Ocean. Snow accumulation in the Sierra Nevada was below normal, reducing spring meltwater feeding the Sacramento River and San Joaquin River. Atmospheric circulation anomalies near the Aleutian Low and the North Pacific High altered the frequency of Pacific storms that normally replenish reservoirs such as Lake Shasta and Lake Oroville. Hydrologists compared conditions to past events like the 1976–1977 drought and examined teleconnections with Tropical Pacific sea surface temperatures measured by researchers affiliated with institutions such as Scripps Institution of Oceanography, National Oceanic and Atmospheric Administration, and University of California, Berkeley.
Winter 1982–1983 saw mixed precipitation influenced by a strong 1982–83 El Niño, but subsequent 1983–1984 and 1984–1985 seasons delivered below-average precipitation across northern and central California. Reservoir storage trends at Shasta Dam, Folsom Lake, and Oroville Dam declined through 1984. Summer low flows in the Sacramento–San Joaquin River Delta intensified salinity intrusion affecting infrastructure like the Contra Costa Water District intakes and the State Water Project, while groundwater extraction increased around the San Joaquin Valley and Santa Clara Valley. By late 1984, water managers in Los Angeles, San Francisco, and Sacramento County had implemented diversions and restrictions as conditions persisted into 1985.
Declines in Sierra snowpack and reservoir levels reduced allocations from the Central Valley Project and the State Water Project to irrigation districts such as the Westlands Water District and the Turlock Irrigation District. Farmers in the Central Valley faced fallowing, reduced cotton and almond acreage, and increased reliance on groundwater, exacerbating subsidence in areas monitored by U.S. Geological Survey programs. Hydroelectric generation at Shasta Dam and Oroville Dam fell, shifting demand to thermal plants overseen by utilities like Pacific Gas and Electric Company and Southern California Edison. Urban suppliers including Metropolitan Water District of Southern California and the San Francisco Public Utilities Commission instituted conservation measures and reduced nonessential water use.
Crop losses and reduced harvests affected commodity markets tied to exchanges such as the Chicago Board of Trade and local commodity handlers in Fresno. Rural communities in counties like Kern County and Stanislaus County experienced employment declines in agricultural sectors, while municipalities faced budget stress related to water purchases. Environmental impacts included habitat contraction for species in the Sacramento–San Joaquin River Delta and stress on migratory runs of Chinook salmon and steelhead trout protected under state programs and monitored by the California Department of Fish and Wildlife. Wetland areas associated with the San Joaquin River National Wildlife Refuge and salt marshes near San Pablo Bay were affected, influencing conservation efforts by organizations such as the Audubon Society and the Nature Conservancy.
State and federal responses involved coordination among California Department of Water Resources, U.S. Bureau of Reclamation, Metropolitan Water District of Southern California, and county water agencies to allocate scarce deliveries, prioritize municipal and industrial uses, and implement voluntary and mandatory conservation. Emergency declarations in some counties enabled financial assistance and infrastructure projects under programs administered by the Federal Emergency Management Agency and the U.S. Department of Agriculture. Investments were made in groundwater monitoring by U.S. Geological Survey and in demand management measures promoted by the California Public Utilities Commission and local water districts. Policy discussions during and after the event influenced later legislation and planning at the California State Legislature and regional planning bodies.
Post-event analyses by researchers at Scripps Institution of Oceanography, California Institute of Technology, University of California, Davis, and National Oceanic and Atmospheric Administration attributed the drought’s character to a combination of reduced precipitation from altered Pacific storm tracks and multiyear deficits in Sierra snowpack. Streamflow records on the Sacramento River and San Joaquin River showed marked departures from historical means compiled by the U.S. Geological Survey. Studies compared atmospheric river frequency, jet stream positioning, and sea surface temperature anomalies to better understand reservoir inflow deficits, informing hydrological modeling used by agencies like the California Department of Water Resources.
Recovery after 1985 involved a return to near-normal precipitation and reservoir refill influenced by subsequent storm seasons and El Niño variability. The drought prompted enhancements in statewide water planning, expanded groundwater monitoring networks, and renewed emphasis on integrated water resource management among entities such as the Bay Area Water Supply and Conservation Agency and the Central Valley Flood Protection Board. Lessons influenced future responses to events like the 2011–2017 California drought and reforms in water allocation policy debated in the California State Assembly and implemented by agencies including the California Water Resources Control Board. The episode reinforced the need for diversified supply portfolios including storage at sites like Lake Oroville, demand management by Metropolitan Water District of Southern California, and ecosystem considerations championed by conservation groups.