United States: Water surpluses in Upper Midwest, Northwest, deficits in the South

November 30, 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 South, especially Alabama and Georgia and across their shared borders with Tennessee and North Carolina; and in the Northeast, especially in New England, Long Island, and Pennsylvania extending to Ohio and West Virginia. Primarily moderate deficits are forecast for Southern California, Utah, Arizona, New Mexico, Oklahoma, Arkansas, with deficits of greater severity forecast in Colorado.

Surpluses are forecast in western Wisconsin, southern Minnesota into northern and eastern Iowa, with exceptional severity in southwestern Minnesota. Exceptional surpluses are also forecast in northeastern North Carolina. Both deficits and surpluses are forecast for the Northwest, though primarily surpluses are expected in eastern Washington and southeastern Idaho.

Outside the contiguous US, surpluses of varying severity are forecast for the island of Hawaii, Maui, Kaho’olawe, Lana’i, and Moloka’i; and in Alaska from Bristol Bay north through the Nushagak River watershed. Deficits are forecast for much of the rest of Alaska and for Puerto Rico.

Impacts
Climate change may already be causing some Americans to relocate as public housing in disaster prone areas is not being rebuilt after natural disasters. Shifting patterns of climate are also changing the distribution of diseases, including skin and waterborne diseases, according to results of a new study in the Journal of the American Academy of Dermatology.

The Great Salt Lake has dropped 11 feet due to drought and diversions of 40% of the natural inflow. The loss of water has increased the salinity of the lake, threatening the brine shrimp and waterfowl populations and the industries that depend on them. The low water levels coupled with high temperatures is also responsible for unprecedented toxic algal blooms in Utah Lake that affected many people and closed public access to the lake.

The Colorado River supply may not be able to fulfill all of the region's growing demand for water and may require federal regulation and restrictions by 2018, a team from the University of Colorado has found.

Along the southeastern coast, trees in coastal woodlands are dying from saltwater intrusion as a result of sea level rise.

Following several months of drought in the southeastern U.S., wildfires in Tennessee have been causing the evacuation of thousands of people.

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

As seen in the November through January map, oranges and reds – indicating water deficits – will dominate much of the US South. Moderate to exceptional deficits are forecast in southern Indiana, southern Ohio, Kentucky, Tennessee, western North Carolina, western South Carolina, Georgia, Alabama, Mississippi, Arkansas, Louisiana, and parts of Florida including Lake Okeechobee. Deficits of similar severity are also expected in southeastern Pennsylvania, eastern Maryland, New Jersey, and in central Colorado and western Nebraska. Primarily moderate deficits are forecast for Southern California, Arizona, New Mexico, Texas, Oklahoma, western Kansas, North Dakota, South Dakota, northwestern Minnesota, and the northern portion of Michigan’s Lower Peninsula.

A large block of blue – indicating a forecast of moderate to exceptional surpluses – is forecast to emerge in the Northwest, which will be especially severe in Washington and Idaho. Moderate surpluses will emerge in northwestern California and in northern Nevada. Surpluses are also forecast along the Upper Mississippi River encompassing southern Minnesota, much of Wisconsin, and northern Iowa. Moderate to extreme surpluses will emerge in southern Michigan and eastern North Carolina.

From February through April the severity of both deficits and surpluses is forecast to diminish considerably, and some states in the Midwest and Northeast will transition to normal or near-normal conditions. However, much of the Northwest and aforementioned areas in the Upper Midwest will remain in conditions of moderate to extreme water surplus. Surpluses will emerge along the Missouri, Platte, and Yellowstone Rivers and in western Montana. Moderate deficits will persist in South Carolina, Georgia, and Florida.

The final quarter of the forecast period (May through July 2017) indicates that moderate deficits will emerge in the West, Wisconsin, Michigan, the Northeast, Georgia, and Florida.

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