United States: Intense water surpluses to continue in W, SW states

25 May 2023

THE BIG PICTURE
The 12-month forecast ending in January indicates major surpluses to persist in many of the western and southwestern continental states. Deficits of varying intensity are expected to endure in isolated pockets of the Pacific Northwest and New Mexico, as well as noncontiguous areas of the U.S.

Extreme to exceptional surpluses are expected to occur in the following areas:

California, throughout much of the state. Central areas of the state are expected to experience the highest intensity anomalies, particularly in territories near the Sequoia and Sierra National Forests.
Central to northeastern Nevada, appearing throughout Eureka County and continuing into Elko and Lincoln County.
Pockets throughout western New Mexico, appearing throughout the Navajo Nation Off-Reservation Trust Land, McKinley County, and the Gila National Forest.
Southeastern Idaho, with the highest intensity surpluses appearing in areas near and throughout Caribou County.
Southwestern Colorado, throughout La Plata County.
West-central Montana, in areas east of the Helena-Lewis and Clark National Forest.
Northern and western Utah, widespread throughout Box Elder County and continuing further south into Salt Lake City, Iron County, and Washington County.
Various regions of Alaska, with the most concentrated anomalies appearing in western coastal regions of the North Slope Borough, as well as northern regions of the Lake and Peninsula Borough.

Extreme to exceptional deficits are anticipated in several areas, including:

Central Oregon, in areas near Wasco County. Deficits of milder intensity, mostly moderate, are expected to continue north across central Washington through the Yakama Indian Reservation and Kittitas County.
Central Idaho, near the Salmon River Mountains.
Southwest New Mexico, appearing near the city of Yuma.
Northeast Utah, in areas north of the Ashley National Forest.
Southeast Louisiana, near the city of New Orleans and throughout the Plaquemines Parish.
Central Florida, in areas within and surrounding Levy County.
Northern New York, in an isolated area near the town of Massena.

Notable deficits are anticipated outside of the Continental U.S., mostly of severe intensity. Affected areas include:

Northeast Alaska, near the Arctic National Wildlife Refuge and east of the Chalkyitsik area.
Puerto Rico, widespread throughout the island.

The 3-month maps (below) show the evolving conditions in more detail.

FORECAST BREAKDOWN
The forecast through July 2023 indicates existing surpluses in the western and southwestern states to persist, specifically in California, Nevada, southern Idaho, and western Colorado. Moderate to severe deficits are expected to appear in central states, such as Nebraska and Kansas, which spread further into northeastern states including Illinois, Indiana, and much of Pennsylvania.

Outside of the Continental U.S., surpluses are expected to persist in Alaska’s western coastal regions of the North Slope Borough, as well as northern regions of the Lake and Peninsula Borough. Severe deficits are expected to continue in northeast Alaska, near the Arctic National Wildlife Refuge and east of the Chalkyitsik area, as well as throughout Puerto Rico.

From August through October 2023, intense surpluses in Nevada, Utah, Idaho, and California are expected to continue, with transitional conditions appearing in southern California, throughout the counties of Santa Barbara and San Luis Obispo.

The forecast for the final months – November 2023 through January 2024 – predicts intense surpluses in Nevada, Utah, Idaho, and California to persist, with mild surpluses appearing in southeastern states such as southern regions of Georgia and northern Florida.

Please note that WSIM forecast skill declines with longer lead times.

IMPACTS
California Gov. Gavin Newsom extended an executive order to divert runoff water from the Sierra Nevada’s historic snowpack season. The order was issued in an effort to assist in recharging groundwater reservoirs across the state of California. Officials expect to increase the flow of several streams, including the Kern River, to reduce the flooding threat along the Tulare Lake Basin. This region is home to some of the largest agricultural productions in the state, including corn, cotton, grapes, alfalfa, almonds, and pistachios.

Experts reported that 80% of the near record-breaking snowpack accumulated in the Sierra Nevada this season has not melted yet. As of May 1st, the Sierra Nevada snowpack was 254% of its historical average, which is the second highest May 1 reading since 1950, when modern records began. The highest reading was in 1983, when snowpack was reported at 289% over its historical average. Additionally, 49.2 inches of snow water equivalent remains frozen across the Sierra.

A report published this week estimates that most workers in the small Central Valley community of Planada, a town recently destroyed by flooding, are ineligible for federal disaster aid or unemployment insurance. The community was one of the first towns in California to be hit in early January by back-to-back storms, which submerged the town and its nearby agricultural fields. Even those who do qualify are finding that the relief money is far from enough to restore their homes that were damaged by the storms. Months later, residents are still struggling to get by, with local leaders pleading for more help, stating that without assistance, the rural community of 4,000 might never fully recover.

Larry O’Neill, an associate professor at Oregon State University’s College of Earth, Ocean and Atmospheric Science, recently stated that the three-year period from October 2019 to September 2022 was easily the worst in state history for Central Oregon. “What made this current drought so much worse than previous droughts for all three counties is that extremely warm summers caused increased water loss through evaporation from soils and vegetation,” O’Neill said. Though Idaho recently experienced a wet winter and spring in Idaho, the counties of Deschutes, Crook, and Jefferson still remain in varying levels of drought.

NOTE ON ADMINISTRATIVE BOUNDARIES
There are numerous regions around the world where country borders are contested. ISciences depicts country boundaries on these maps solely to provide some geographic context. The boundaries are nominal, not legal, descriptions of each entity. The use of these boundaries does not imply any judgement on the legal status of any territory, or any endorsement or acceptance of disputed boundaries on the part of ISciences or our data providers.

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