United States: Water deficits to lessen, surpluses develop in Upper Mississippi Basin

September 22, 2016

The Big Picture
The 12-month map (below) indicates that water deficits ranging from moderate (5 to 10 years expected frequency) to exceptional (greater than 40 years) are forecast for the US Northeast, especially in New England, Pennsylvania and western New York extending west to Ohio and Michigan, and the South especially along the Georgia – Alabama border. Deficits of equal severity are also forecast for much of the western half of the US, especially western Oregon, with both deficits and surpluses forecast in the Rocky Mountain States.

Surpluses are forecast in northwestern Wisconsin; southeastern Minnesota into northeastern Iowa; Nebraska; an area near Abilene, Texas; southern Louisiana; and Hawaii.

Impacts
The Mississippi River at Guttenberg, Iowa rose nearly two feet in three days by August 27 after torrential rains, but conditions on the nearby Turkey River were worse. In Elkader the Turkey River crested at 10.5 feet (3.2 meters) above flood stage, and 6.6 feet (2 meters) above was reported at Garber. Sandbagging helped mitigate the damage but several roads were closed in the Osterdock and Millville area. In all, five counties were declared disaster areas, eligible for state funds.

Minnesota - Iowa's northern neighbor - has also been uncommonly wet. In August farmers in the south faced soggy fields and standing water after receiving as much rain in 28 days as they normally receive in 2 to 3 months. Water advisories were in effect in Willmar where flooding inundated the waster water treatment plant. September storms have dumped heavy rain over the Twin Cities, flooding major highways, stranding cars, and forcing the Minnesota Department of Transportation to bring in snow plows. According to the National Weather Service, Waseca received 13.91 inches of rain in 48 hours.

In southwestern Wisconsin flooding and landslides closed roads, schools, and washed out bridges. The Richland School District canceled classes, students at St. John's Lutheran School and Parkview Primary in Mayville were sent home, and campers were evacuated from Sidie Hollow County Park near Viroqua.

It's been a wet couple of months in Maui, Hawaii, as well. This August was the second wettest August on record - second only to last year - as reported by the National Weather Service. A recent September storm dropped 10 inches of rain in just a few hours, flooding parks and homes and knocking out a water line.

In New England conditions remain dry. Additional water use restrictions have been imposed on some Central Massachusetts communities as the reservoir systems that services Worcester, Paxton, Holden and parts of West Boylston registered only 55.1 percent full on Sept. 1 against the September average of 81.7 percent.

Boston had its driest summer on record - precipitation 6.5 inches below average - and its hottest August. A quarter of Massachusetts is categorized with conditions of "extreme drought" by the US Drought Monitor, the first time the 16 years of the Monitor's existence.

Maine's Drought Task Force met for the second time this year - just the second time since 2002 - to address mounting concerns over the drought, which has been building for three years. The state's southern basins are low and continuing to drop, according to the US Geological Survey. The USDA has declared several Maine counties drought-stricken, offering financial assistance to farmers in York, Cumberland and Oxford Counties. The Small Business Administration will step in to aid small businesses affected by the drought.

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

From September through November a nearly solid expanse of oranges and reds – indicating moderate (5 to 10 years) to extreme (20 to 40 years) water deficits – runs throughout the eastern US. A large pocket of blue tones – indicating a forecast of moderate to exceptional surpluses – follows the Upper Mississippi River and encompasses southern Minnesota, much of Wisconsin, eastern Iowa, and northern Illinois. Surpluses are also forecast during this period for Nebraska, southern Louisiana, Texas near Abilene and east. Dark red paths of exceptional deficits trace the Missouri and Yellowstone Rivers as they wind across the northern US. Though not as severe as in the prior three months, deficits of varying severity are forecast for much of the western half of the US.

From December through February deficits across the US are forecast to diminish in severity, though moderate to severe (10 to 20 years) deficits will persist on the Missouri and Yellowstone Rivers, eastern Virginia, and Florida. Surpluses will persist in Minnesota and Wisconsin; will continue to emerge southward in Illinois and Iowa; and will emerge in Missouri, northern Arkansas, and eastern Oklahoma. Surpluses will also emerge dotted throughout northern Utah, northeastern Nevada, southern Wyoming, Idaho, and eastern Washington.

The final quarter of the forecast period (Mar-May 2017) indicates water surpluses throughout the Rocky Mountain States, especially along rivers.

Outside the contiguous US, scattered moderate to extreme deficits are forecast through May for Alaska in a wide arc from the Southwest Region, to the eastern part of the Far North Region, and into the Southcentral Region. Surpluses are forecast northward from the Alaska Peninsula into the Interior Region. Much farther south in Hawaii surpluses are forecast for the island of Hawaii, particularly the western half, through March, but may be especially widespread and severe in September.

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