United States: Water deficits in the West, SW, NW, ND, Deep South

20 April 2021

THE BIG PICTURE
The 12-month forecast ending December 2021 indicates widespread water deficits of varying intensity in the U.S. West, Pacific Northwest, Southwest, Rocky Mountain States, Northern Plains, and Texas. Deficits are expected to be exceptional in Southern California, Utah, Arizona, and many other pockets in the West. Moderate to extreme deficits are forecast for North Dakota.

Moderate deficits will follow the Missouri River through South Dakota. A pocket of moderate surplus is forecast in central Nebraska spanning the Platte River.

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In the Great Lakes Region, severe deficits will follow the Kankakee River in northern Illinois and into northern Indiana. Primarily moderate deficits are forecast for Michigan and northwestern and eastern Ohio, but anomalies will be more intense in western Pennsylvania. New York’s Finger Lakes Region can expect moderate deficits, but deficits will be exceptional along the St. Lawrence River. In New England, deficits are forecast for Vermont and New Hampshire.

The South Atlantic States and Deep South can also expect deficit conditions. Anomalies will be exceptional in southern Alabama and extreme near Savannah, Georgia. Deficits will cover much of Florida, moderate in the Panhandle but severe to extreme between Jacksonville and Orlando and south of Lake Okeechobee. Surpluses are forecast near the Keys.

Outside the contiguous U.S., surpluses are forecast for most of the Hawaiian Islands. Alaska can expect deficits in its northeast quadrant; in the center of the state at the confluence of the Yukon and Tanana Rivers; in a large block east of Norton Sound; and around Anchorage and Valdez. Surpluses are forecast west of Bethel, near Iliamna Lake, and near Juneau. In Puerto Rico, mild deficits are expected in the northwest.

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

The forecast through June indicates that surpluses will shrink considerably as deficits emerge. While the center of the country will see relatively normal conditions, deficits of varying intensity will cover much of the West, Southwest, Rockies, Texas, Dakotas, Michigan, northern Ohio River Watershed, the Northeast, South Atlantic, and Deep South. Anomalies will be exceptional in North Dakota’s eastern half including the James River Watershed. Many pockets of exceptional deficit are forecast in the U.S. West, especially in Utah and Arizona. Nearly all of Texas can expect deficits, with severe deficits forecast between Dallas and Austin and deficits reaching across the Red River into Oklahoma. Elsewhere, regions with a forecast of intense deficit include western Pennsylvania, the middle reaches of the Alabama River, and the Lake George region in northern Florida. Surpluses are forecast in Nebraska spanning the Middle Platte River.

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From July through September, deficits will shrink and downgrade overall, but will intensify in the San Francisco Bay Area, Pacific Northwest, and Northern Rockies. Other areas in the region with a forecast of intense deficit include the Humboldt River in Nevada and the Snake River in Idaho. severe deficits will emerge on the Missouri River - becoming extreme between the North Dakota/Montana border and Fort Peck Lake - and on the Arkansas River through Kansas. Deficits of generally lesser intensity will persist in Michigan, the Kankakee River, and pockets from East Texas through the Deep South, Florida Panhandle and South Atlantic States. In New England, deficits will shrink though extreme deficits are forecast on the Vermont/New Hampshire border and deficits will emerge in southern Maine.

The forecast for the final months – October through December – indicates normal conditions overall with deficits of varying intensity in the Rockies and some moderate deficits in the South Atlantic States and northern Florida.

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

IMPACTS
Dry conditions affect many regions of the U.S. with no sign of imminent relief. As of 15 April, over 45 percent of the lower 48 states are experiencing some level of drought according to NOAA’s National Integrated Drought Information System. Around 92 million people are affected and over 72 million acres of crops.

The drought is particularly widespread and intense in the West and Southwest. Nearly all of California is abnormally dry with 77 percent classified as being in “severe drought” and over 38 percent in “extreme drought,” conditions that reduce grazing land, increase requirements for supplemental feedstock, and place unsustainable demands on limited irrigation supplies.

Along the California-Oregon border, the drought has taken the discussion up a notch as authorities attempt to balance water allocation from a massive irrigation project on the Upper Klamath Lake between farmers and regional tribes.

The U.S. Bureau of Reclamation is predicting that water levels in Western storage could shrink to historical lows, triggering cuts to Arizona and Nevada from the Colorado River System .

Recent precipitation in North Dakota has done little to alleviate drought conditions there, where nearly 76 percent of the state is in severe drought. Many farmers delayed planting due to dry conditions and ranchers are facing reduced forage productivity.

Torrential rainfall at the end of March created flash flooding in Tennessee, inundating homes and roads as many creeks overflowed. Seven deaths were reported.

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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