United States: Water deficits will increase in the Central Plains

21 October 2020

THE BIG PICTURE
The 12-month forecast ending June 2021 indicates widespread water deficits in the southwest quadrant of the continental U.S. from Wyoming through West Texas and reaching west through California. Deficits will be exceptional in many areas including nearly all of Arizona and large blocks in New Mexico, Utah, and as far north as western Nebraska. Severe to extreme deficits are forecast on the Canadian River through western Oklahoma and the Texas Panhandle, and primarily moderate deficits following the Gulf Coast in Texas.

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The Pacific Northwest can expect deficits in central Oregon and pockets of surplus in Washington, northern Idaho, and western Montana along with a few small pockets of deficit as well.

In the Upper Midwest, moderate surpluses are forecast on Nebraska’s northern border and poking into South Dakota. Some pockets of surplus are also forecast in northwestern Minnesota. Iowa will see deficits that will be extreme in the middle region of the Des Moines River. Around the Great Lakes, surpluses are forecast for northeastern Wisconsin into northern Michigan. Some moderate deficits will skirt Michigan’s southern border and reach from northern Illinois through Ohio, becoming intense and widespread in western Pennsylvania. Deficits of varying intensity are expected in the U.S. Northeast with exceptional deficits in the St. Lawrence River region of Upstate New York and pockets in Vermont, New Hampshire, and Maine.

Surpluses are forecast from Washington, D.C. past Richmond, Virginia into North Carolina, and will be extreme east of D.C. and extreme to exceptional from Richmond to the North Carolina border. Moderate surpluses are expected spanning the Tennessee/North Carolina border, and moderate to severe surpluses in Arkansas.

Deficits are expected in much of Florida outside of the Panhandle with extreme deficits northwest of Orlando and exceptional deficits south of Lake Okeechobee and around Lake Istokpoga. Pockets of deficit are also forecast for southeast George, central Alabama, and New Orleans.

Outside the contiguous U.S., surpluses are forecast for much of Hawaii. Alaska can expect deficits near Kodiak, Anchorage, and past Valdez; in the northeast; and in pockets of the west. Surpluses are forecast north of Iliamna Lake, in the center of the state, and from Denali east to the Canadian border.

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

From October through December the overall forecast indicates that surpluses from the Lower Mississippi River through the Virginias will nearly disappear, leaving a few pockets in Arkansas and in the east from Washington, D.C. to Raleigh, North Carolina. Deficits in the U.S. West and Southwest will shrink and downgrade considerably becoming mild to moderate overall though intense deficits are forecast in some regions including Colorado and pockets of Utah, western Nebraska, New Mexico, and the central Panhandle Plains of Texas. Deficits will downgrade slightly in western Iowa but will emerge in many parts of Nebraska, Kansas, northern Oklahoma, southwestern Missouri, and pockets of eastern and southern Texas.

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Pockets of surplus are forecast for the Pacific Northwest and western Montana, and pockets of deficit in North Dakota. Mixed conditions are expected in South Dakota and Minnesota, and moderate surpluses in northern Michigan and east-central Wisconsin. Moderate deficits will continue in the northern Ohio River Watershed, but deficits will remain intense in western Pennsylvania and in the U.S. Northeast. In Peninsular Florida, deficits will be intense in the south but will downgrade slightly north of Orlando. Moderate to extreme deficits will increase in Alabama and southeastern Georgia.

From January through March 2021, normal water conditions will return to many regions as deficits shrink but intense deficits are forecast for central Colorado, New Orleans, and Peninsular Florida. Deficits will shrink and moderate in northern Maine. Deficits elsewhere include Iowa, western Wyoming, New Mexico, and coastal Texas. Surpluses are forecast for Wisconsin, northern Michigan, northwestern Minnesota, from central South Dakota into Nebraska, and pockets of Montana and Idaho.

The forecast for the final months – April through June 2021 – indicates pockets of intense deficit in New Mexico, and moderate deficits in Peninsular Florida, New Orleans, and pockets of central Colorado, Arizona, and Southern California. Isolated pockets of moderate surplus are expected in the Northern Rockies and Pacific Northwest.

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

IMPACTS
The drought in Colorado’s Western Slope has fueled a number of fires this season but none bigger than the Cameron Peak Fire west of Fort Collins. Now the largest fire in the state’s history, the Cameron Peak blaze has burned over 167,000 acres in the Arapaho and Roosevelt National Forests. As of mid-October, 38 percent of Colorado was classified as being in severe drought and 42 percent in extreme drought.

Among a half dozen other fires lighting up the region, documented on the National Wildfire Coordinating Group’s incident website, is the Middle Fork Fire in Routt National Forest near Steamboat Springs. Ranchers in the region say fire threat has forced them to pull stock off the national forest grazing lands and hay production is down by 30 to 50 percent due to dry conditions. One state climatologist notes that Colorado, already in its third year of a poor monsoon, is facing La Niña conditions that usually bring more dryness.

Federal tax relief has been extended for farmers and ranchers in 46 states suffering from drought, giving them another year to defer tax gains on the forced sale of livestock and at least two additional years to replace the animals.

By the end of September, every reservoir in New Mexico was below average capacity and the largest, Elephant Butte, was at a mere 4 percent. Nearly all of the state is at some level of drought, triggering implementation of water shortage allocation agreements on the Jemez, Gallinas, Animas and Chama rivers. Santa Fe is currently in exceptional drought; through October, the city has received just 38 percent of its normal rainfall.

Characterizing it as “dust-bowl-like conditions,” the CEO of Kansas Wheat, a wheat-growers advocacy organization, lamented the lack of rainfall in the state’s southwestern region and its potential negative impact on the winter red wheat crop.

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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