United States: Water deficits from Ohio to the Gulf

19 December 2016

The Big Picture
Apparent in the 12-month forecast through August 2017 (below) is the persistence of significant water deficits from the Ohio River Valley south to the Gulf, especially in Alabama and Georgia and across their shared borders with Tennessee and North Carolina. Deficits are also forecast throughout the Northeast, which may be particularly severe in Pennsylvania and Maryland, and in the northern half of Michigan’s Lower Peninsula, and Colorado. Deficits of lesser severity are expected from the Northern Plains southward through Texas.

Surpluses are forecast in western Wisconsin, southern Minnesota into northern Iowa, and in northeastern North Carolina. Both deficits and surpluses are forecast for the Pacific Northwest, though primarily surpluses are expected in Washington.

Outside the contiguous US, surpluses of varying severity are forecast for the island of Hawaii, Maui, Kaho’olawe, Lana’i, and Moloka’i. Surpluses are also forecast on the Alaskan Peninsula near Pilot Point and from Bristol Bay north through the Nushagak River watershed. Deficits are forecast for much of the rest of Alaska and for western Puerto Rico.

Impacts
Federal disaster funding has been approved for Tennessee’s Sevier County following devastating wildfires in late November and early December which killed 14 people, injured 191, displaced thousands, damaged 2,400 structures, and ravaged nearly 18,000 acres. Damages from the fires – caused by arson and exacerbated by severe drought in the region – are estimated at around $500 million.

Drought-related impacts have affected other states in the southern US as well. Georgia has spent $3.1 million fighting fires this year – a figure much higher than in previous years – and firefighters from as far away as Arizona, California, and Alaska helped battle fires in North Georgia. Water levels at Lake Lanier, metro Atlanta’s source of drinking water, measured 10 feet below full capacity in mid-December.

Though recent rains have improved conditions in Alabama, statistics from the National Drought Mitigation Center indicate that 96 percent of the state remains in drought, with nearly 20 percent classified as “exceptional drought,” including the Birmingham metropolitan area. The US Small Business Administration will make federal loans available in Lauderdale County for some businesses affected by the drought.

Forecast Breakdown
The 3-month maps (below) show the evolving conditions in more detail. What is readily apparent is that severe to exceptional deficits are forecast to persist through February from Ohio to the Gulf but will diminish in severity thereafter, shown on the maps as vast areas of dark red and deep orange giving way to gold and yellow tones.

From December through February, however, much of the area from Pennsylvania and Ohio southward through the Gulf is forecast to experience moderate to exceptional deficits, and deficits will emerge throughout Louisiana and into Florida. Much of the far Northeast, with the exception of Vermont, is expected to return to near-normal conditions. Surpluses will continue to emerge in Wisconsin, southern Minnesota, and northern Iowa during this period, which could reach exceptional severity from Brainerd, Minnesota south through Minneapolis and into Iowa. Exceptional surpluses are also forecast for much of Idaho, northwestern Montana, and northeastern Washington.

From March through May the severity of both deficits and surpluses is forecast to diminish considerably, and some states in the Midwest will transition to normal or near-normal conditions. Primarily moderate deficits are forecast across much of Maine, southern New Hampshire, Massachusetts, Rhode Island, and Connecticut, and further south along the Atlantic Seaboard from North Carolina through Florida. Moderate to isolated exceptional surpluses will continue to emerge in Washington, Idaho, and western Montana. Moderate surpluses are forecast along the Yellowstone River in Montana and the Missouri River in North Dakota.

The final quarter of the forecast period (June through August 2017) indicates moderate to severe deficits in the West and throughout the southern Atlantic Seaboard states.

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