United States: Intense water surplus forecast from S. Dakota into Texas

30 July 2019

THE BIG PICTURE
The 12-month forecast ending March 2020 indicates that water surpluses of varying intensity will affect a broad path down the middle of the nation through the Mississippi River Basin as well as westward well into the Missouri, Arkansas, and Red River Basins, and north through much of Michigan. Surpluses are expected to be extreme to exceptional in South Dakota, Kansas, southeastern Minnesota, northern Michigan, and along portions of the Missouri and Arkansas Rivers. Severe to extreme surpluses are forecast along the Mississippi River. Texas, too, can expected surpluses in the western Edwards Plateau and in the northeast.

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Surpluses are also forecast scattered throughout the Rockies, in eastern Nevada and along the Colorado River. Primarily moderate surpluses are forecast for central California. On the opposite coast, moderate surpluses are forecast for the U.S. Northeast.

Deficits are expected in the Pacific Northwest, north-central Minnesota, and along the Atlantic coast from North Carolina trailing into pockets of Florida. Deficits will be intense in North Carolina.

Outside the contiguous U.S., surpluses are forecast for much of Hawaii. In Alaska, surpluses are forecast in the Koyukuk River watershed the center of the state, and north of Bristol Bay in the south. Moderate to extreme deficits are forecast in the Tawana River region east and south of Fairbanks, and near Anchorage and Valdez. Severe deficits are forecast for western Puerto Rico and moderate deficits in the east.

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

Water surpluses of varying intensity will continue to cover a significant portion of the central U.S. through March 2020.

From July through September 2019, observed surpluses along the Mississippi River, its tributaries, and states on the western bank of the river will moderate. However, significant surpluses are forecast in a column from South Dakota through central and eastern Texas, and will include extreme to exceptional anomalies in many areas, particularly South Dakota. Surpluses of varying intensity are expected in parts of the Rockies including southern Idaho and southern Montana, Wyoming, Colorado; as well as in western Utah, eastern Nevada, and central Arizona. Primarily moderate surpluses are forecast for California and into pockets of central Oregon, but conditions of both deficit and surplus are also expected in California as transitions occur, with some moderate deficits emerging north of San Bernardino. Moderate surpluses are forecast for much of Michigan, pockets of the Ohio River Valley, and pockets of the U.S. Northeast.

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Deficits of varying intensity are forecast for the Pacific Northwest. Deficits are also expected in northwestern Minnesota, the western third of Michigan’s Upper Peninsula, and along the Atlantic coast in North Carolina where anomalies will be extreme. Some pockets of moderate deficit are forecast from South Carolina through southern Alabama and into the Florida Panhandle.

From October through December, surpluses will persist in a column from South Dakota through Oklahoma, moderating somewhat in eastern portions of the affected states but persisting with intensity in South Dakota. Surpluses will shrink in Texas, downgrade in the Upper Mississippi, and conditions will normalize in the Lower Mississippi region. Primarily moderate surpluses are forecast for much of Michigan’s Lower Peninsula and in northeastern Ohio. Conditions in the U.S. Northeast will become nearly normal. Back in the West, surpluses of varying intensity will persist in parts of the Rockies, western Utah, Nevada, and pockets of eastern Oregon; and will shrink considerably in California, with much of the state returning to normal. Surpluses will also shrink in central Arizona. Deficits in the Pacific Northwest will nearly disappear, as well as in Michigan’s western Upper Peninsula; and deficits along Minnesota’s northern border will shrink considerably. Deficits in coastal North Carolina will downgrade and merely mild deficits are forecast for its southern neighbors. A small pocket of intense deficit will persist in southern Florida south of Lake Okeechobee.

The forecast for the final months – January through March 2020 – indicates a pattern of surplus anomalies similar to the forecast for the prior three months with a slight increase in moderate surpluses in the Northeast and in southern California.

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

IMPACTS
Indiana governor Eric Holcomb requested from the U.S. Department of Agriculture Secretary a disaster designation in 88 counties due to losses from flooding and heavy rains. Of Indiana’s 92 counties, 88 of them reported losses or damages of one crop meeting at least 30 percent, making them eligible for the disaster designation.

Flash flooding knocked homes off their foundations and washed out roads in several counties in West Virginia after a severe storm late last month.

Water levels on the Mississippi River began receding toward normal levels mid-July, resuming shipping traffic, which had been closed for much of this season following record rainfalls in the Midwest.

A pregnant mother and her nine-year-old son were killed in a flash flood in Pennsylvania this month when they were swept down the Manatawny Creek by floodwaters inside a car. Heavy storms caused the flooding that knocked down trees and power lines in many areas.

Two people were killed when flooding in North Dakota washed out a highway on the Standing Rock Reservation in Sioux County this month, creating a chasm 30-40 feet wide and 60-70 feet deep.

About $3.3 million worth of damage was caused to 94 homes in northwest Charlotte, North Carolina last month, when the Catawba River flooded following heavy rain.

Heavy thunderstorms dropping up to eight inches of rain across southern Louisiana flooded downtown New Orleans mid-July, forcing the closure of City Hall.

Nearly a month’s worth of rain, totaling two to four inches, fell in one hour in Washington, D.C. this month, prompting water rescues and closing several roads downtown and in surrounding areas, and seeping into the basement of the White House.

This season’s spillway openings in Louisiana, releasing deluges of freshwater into parts of the coastal Gulf of Mexico, are at least partly responsible for the hundreds of dolphin deaths since February.

Rising costs of flood risks and insurance have priced lower- and middle-class families, who some reporters are calling New York’s “invisible climate migrants,” out of their homes in New York City’s Rockaway neighborhood in Queens since Hurricane Sandy devastated the area in 2012.

The six-year drought in California beginning in 2011 and ending in March of this year contributed to mass die-offs of trees in the central and southern Sierra Nevada mountains, according to a recent study. Coauthors of the study described a '“tipping point” in 2015, at which water demand of the forest exceeded annual precipitation plus stored subsurface water.

Record-high June temperatures increased drought conditions in Washington, the state currently most affected by drought.

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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