United States: Water deficits ahead for South Atlantic States, surpluses Upper Midwest

29 November 2017

THE BIG PICTURE

The 12-month forecast indicates water surpluses in parts of the Upper Midwest, significant deficits in the Southwest, and deficits of varying severity in California, the Lower Mississippi Valley, and the South Atlantic States through Georgia.

Surpluses are forecast in northern Michigan, central Indiana, northern Illinois, Wisconsin, southern Minnesota, western Iowa, southeastern South Dakota, and northeastern Nebraska. Surpluses may be extreme in Michigan’s northern Lower Peninsula, Minnesota, and Nebraska. Surpluses are also forecast for pockets of Idaho, along Florida’s northeast coast, and east of Houston, Texas, though both deficits and surpluses are forecast in these regions as conditions change.

Extreme deficits are forecast for the northwest corner of Washington, severe deficits are forecast for Arizona, and deficits ranging from moderate to extreme are forecast in Nevada, Utah, Colorado, and New Mexico. Primarily moderate deficits are forecast for California, central Texas and the southern tip, and northwestern Minnesota. In the Lower Mississippi Valley moderate to extreme deficits are expected in southeastern Missouri, Arkansas into Louisiana, and central Mississippi. Deficits of similar intensity are forecast for the South Atlantic States from Virginia into the central Florida Panhandle. Deficit conditions reaching extreme intensity are forecast for eastern Maine, and deficits are also expected to pepper the shared border of Ohio and Pennsylvania.

Outside the contiguous United States, surpluses are forecast for Hawaii, moderate deficits for western Puerto Rico, and in Alaska deficits are expected in the eastern half of the state and surpluses in the west.

IMPACTS
As of early November, estimates of insured losses from California's October wildfires exceed $3.3 billion, according to the state's insurance commissioner who warns that those figures may rise. The fires claimed 43 lives, and insurance losses include: partial loss to 10,016 residential properties, total losses to 4,712 residential properties, 728 commercial property losses, 3,291 auto losses, 153 agriculture equipment losses, and 111 watercraft losses.

Excessive precipitation prompted the governor of Illinois to declare a harvest emergency early this month, invoking measures to help the state's agricultural industry deal with rain-related delays. Under recent law the governor's declaration permits agricultural truckloads to temporarily exceed state highway weight limits by 10 percent, speeding transport and making up for time lost during the rain-delayed harvest. The 2017 Illinois corn harvest volume is running 17 percent below last year and 11 percent below the five-year average.

In the three months since Hurricane Harvey deluged Houston, the region has been growing increasingly dry, registering a 12-inch rainfall deficit since September 1. Though Harvey dropped a year's worth of rain in a matter of days, Houston's un-sponge-like clay soil prevented absorption and much of the water slid away into the Gulf of Mexico.

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

Please note that we are well aware of the recent devastation wrought by hurricanes. Readers are advised that inputs used in our Water Security Indicator Model (WSIM), the model used to generate “Global Water Monitor and Forecast Watch List,” have been proven reliable in forecasting broad precipitation patterns, but are not effective for predicting singular events such as tropical storms. Detailed outlooks and analyses of tropical storms are available from NOAA National Hurricane Center.

The forecast for November through January indicates several striking changes from observed conditions in the prior three months. Note the forecast of a transition to deficits in the Gulf Coast States of Texas, Louisiana, and Mississippi. Deficits are expected to be moderate to severe and will also emerge in Arkansas and southern Missouri. Notable as well is the forecast of widespread moderate to extreme deficits emerging in the South Atlantic States from southern Virginia through the central Florida Panhandle. Blues and greens in the East draw attention to the forecast of widespread surpluses of varying severity from the Upper Midwest, through the Ohio River Valley, and extending into the Northeast. Though primarily moderate, surpluses could be exceptional in central Minnesota and extreme in Michigan and northern Illinois.

Primarily mild deficits are forecast across the Plains States and the Southwest, though deficits may be more severe in northwestern Minnesota. A large block of exceptional surplus is forecast for central Nebraska, and some pockets of surplus are expected in central Wyoming and in southern Colorado leading southeast along the Canadian River. Relatively normal conditions are forecast for California, mild surpluses in the Pacific Northwest, a large pocket of exceptional surplus in southeastern Idaho, and small pockets of exceptional surplus peppered across Nevada and northwestern Utah.

As shown in the February through April map, normal water conditions should return to the Ohio River Valley, Mid-Atlantic States, and the Northeast in the spring. Moderate to severe surpluses will continue to emerge in southern Minnesota but severe deficits will persist in the northwestern part of the state. Primarily moderate surpluses will emerge in Iowa and Missouri, and surpluses of greater intensity will persist in eastern Nebraska. Deficits will moderate in the South Atlantic States, the Lower Mississippi Valley, and Texas. Spring will bring merely mild deficits to the Plains, the Southwest, and California. Moderate surpluses are expected in the Northern Rockies and the Pacific Northwest.

The forecast for the final months – May through July – indicates an upgrade in the intensity of deficits in the South, Southwest, and Southern California, and the persistence of surpluses in the Upper Mississippi.

(It should be noted that forecast skill declines with longer lead times.)

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.