United States: Widespread water deficits in the West

18 May 2021

THE BIG PICTURE
The 12-month forecast ending January 2022 indicates widespread water deficits of varying intensity in the U.S. West, Pacific Northwest, Southwest, Rocky Mountains, North Dakota, and Texas. Exceptional deficits are expected in many pockets and will be especially pervasive in Southern California and Arizona. Deficits on the Colorado River will be exceptional surrounding Lake Mead and severe in the river’s upper basin. Moderate to severe deficits are forecast for North Dakota, and moderate deficits will follow the Arkansas River through western Kansas into Colorado.

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A few small, isolated pockets of surplus are expected in the Rockies including exceptional anomalies along the Bighorn River as it crosses from Montana into Wyoming. Small, isolated pockets of moderate surplus are forecast in the Lower Ohio and Lower Mississippi River regions. The South Atlantic States can also expect deficit conditions, primarily moderate but anomalies will be extreme near Savanna, Georgia, and severe in Florida between Jacksonville and Orlando and south of Lake Okeechobee. A few small, isolated pockets of exceptional deficit are forecast in Alabama.

Michigan can expect some pockets of moderate deficit, but anomalies will be somewhat more intense in western Pennsylvania. Deficits will also be intense along the St. Lawrence River in Upstate New York as well as in the northern regions of Vermont and New Hampshire, while moderate deficits are expected in Maine’s southern half.

Outside the contiguous U.S., moderate deficits are forecast for Puerto Rico. In Hawaii, surpluses are expected in Oahu and Molokai and deficits in Maui. Alaska can expect deficits in the northeast, a large block east of Norton Sound, and near Valdez and Anchorage. Surpluses are forecast west of Bethel, near Iliamna Lake, and near Juneau.

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

The forecast through July indicates widespread deficits of varying intensity in the West, Southwest, Pacific Northwest, Rockies, and Texas. Anomalies will be exceptional in some regions, notably western Oregon, the Salmon River Mountains in Idaho, around Lake Tahoe, Utah’s Rocky Mountain region, and western Wyoming. Deficits in North Dakota will downgrade from exceptional to moderate or severe. Moderate deficits will trace the Missouri River through Montana and the Arkansas River through Kansas into Colorado. A small pocket of intense surplus is expected along the Bighorn River as it crosses from Montana into Wyoming.

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The Upper Midwest will see deficits spanning the Minnesota-Iowa border and in Michigan. Deficits in the U.S. Northeast will reach exceptional intensity in a few small pockets. Primarily moderate deficits are forecast in the South Atlantic states and northern Florida. Moderate surpluses are forecast for southern Louisiana and Mississippi and a few pockets in the Lower Ohio River Basin.

From August through October, surpluses will nearly disappear and deficits will shrink considerably and downgrade. Conditions in much of the Plains, Midwest, and Ohio River region are forecast to be normal. Deficits will persist in the Pacific Northwest, Rockies, Northern California, and pockets of the Southwest. Anomalies will be exceptional in western Oregon, the Salmon River Mountains, and the Bear River region in northeastern Utah. Moderate deficits are forecast in the eastern half of Michigan’s Upper Peninsula. Deficits will shrink and downgrade in New England but will increase somewhat in the South Atlantic and South as moderate deficits emerge in Georgia and southern Mississippi and Alabama.

The forecast for the final months – November 2021 through January 2022 – indicates normal conditions overall with deficits in the Middle and South Atlantic regions and pockets of the Rockies, and surpluses in Illinois.

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

IMPACTS
As of mid-May, the entire state of California was classified as being in various stages of drought by the U.S. Drought Monitor with almost 14 percent in “exceptional” drought, the most intense deficit condition. The second highest classification, “extreme,” afflicts a whopping 73 percent. Cal Fire reports over seven times the acreage scorched by fires this year through the first week of May as last year at the same time.

Lake Oroville, the reservoir formed by damming the Feather River in northern California, was at just 42 percent of its capacity at the end of April when spring runoff should keep the water level high. With the reservoir’s steep sides exposed, houseboats in the lake looked like toy boats bobbing in shallow bathwater after someone pulled the plug.

Facing a summer of drought, California’s Division of Water Rights has demanded that Nestle, producers of bottled water brand Arrowhead, reduce its water draw from the San Bernardino National Forest, asserting that the bottler exceeds its annual limit by millions of gallons. Water flowing from the region’s Strawberry Creek eventually reaches 750,000 people through municipal systems.

Pasture and range conditions in the West, Southwest, and Northern Plains are in poor condition due to drought, a critical situation for the beef cattle industry. In Arizona, 90 percent of grazing area is considered to be in poor condition while runner-up North Dakota is at 75 percent. Some ranchers are already culling the herd. The U.S.D.A reports low May hay stocks, down 60 percent below the five-year average in Colorado.

Oregon’s Klamath River Project will turn off the taps of its main canal for irrigators to preserve water during this year’s drought, an unprecedented move since its opening in 1907.

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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