United States: Water deficits will increase in the SW & Deep South

24 March 2021

THE BIG PICTURE
The 12-month forecast ending November 2021 indicates widespread water deficits of varying intensity in the U.S. West, Pacific Northwest, Southwest, Rocky Mountain States, and Texas with anomalies bleeding into the Plains region. Deficits are expected to be exceptional in Southern California, Nevada, Utah, Arizona, New Mexico, and northern Texas. Moderate to exceptional deficits are forecast for North Dakota.

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Deficits are forecast in the Deep South from Louisiana through southern Mississippi, Alabama, Georgia, and South Carolina. Anomalies will be intense in the Mississippi Delta and central Alabama. Deficits will cover much of Florida, moderate in the Panhandle but severe to exceptional between Jacksonville and Orlando. Surpluses are forecast near the Keys.

In the Mid-Atlantic, surpluses are forecast from Chesapeake Bay through much of Virginia and into North Carolina. In the U.S. Northeast, western Pennsylvania can expect deficits ranging from moderate to extreme, and intense deficits are forecast near the St. Lawrence River in Upstate New York. Deficits are also forecast for Vermont, New Hampshire, and southern Maine. In the Great Lakes Region, moderate deficits will follow the Kankakee River in northern Indiana and will skirt Michigan’s southern border and reach into Ohio.

Outside the contiguous U.S., surpluses are forecast for most of the Hawaiian Islands. Alaska can expect deficits in its northeast quadrant; in the center of the state at the confluence of the Yukon and Tanana Rivers; in a large block east of Norton Sound; and around Anchorage and Valdez. Surpluses are forecast west of Bethel, near Iliamna Lake, and near Juneau. In Puerto Rico, moderate deficits are expected in the central north region.

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

The forecast through May indicates that deficits of varying intensity will increase, blanketing much of the West, Southwest, Rockies, Texas, the Deep South, and Florida. Anomalies will be exceptional in many regions including Utah, Arizona, and New Mexico. Deficits in North Dakota will increase, covering much of the state and will be exceptional in the James River Watershed. Deficits will seep into other states in the Plains, emerging in western South Dakota, western and southern Nebraska, and northern Kansas. Nearly all of Texas can expect deficits, and Arkansas will transition from surplus to moderate deficit.

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Surpluses in the Mid-Atlantic States will nearly disappear. Intense deficits will persist in western Pennsylvania, but anomalies elsewhere in the Northeast will shrink, leaving small pockets of surplus and of deficit, primarily in New York.

From June through August, nearly normal conditions are forecast for the Upper Mississippi River and Ohio River Basins, but much of the rest of the nation can expect some degree of deficit. Intense deficits will shrink in the Southwest, increase in Northern California, and persist in Nevada and Utah. Deficits will increase in the Pacific Northwest and Central Plains; downgrade though be severe in North Dakota’s James River region; moderate in the Deep South and Florida; and emerge in North Carolina, in more areas of New England, and in Michigan’s Upper Peninsula.

The forecast for the final months – September through November – indicates that deficits will shrink and downgrade considerably. Pockets of deficit ranging in intensity are forecast for the Rockies, and moderate deficits along rivers in the Plains. Mild to moderate deficits are expected in pockets of the Pacific Northwest and California, in the Upper Midwest, along the Gulf Coast from Louisiana through northern Florida, and in New Hampshire.

Please note that WSIM forecast skill declines with longer lead times.

IMPACTS
The devastating winter storm that struck Texas in February caused an estimated $600 million in agricultural losses to citrus, vegetables, and livestock. In the Rio Grande Valley, 60 percent of the grapefruit crop was lost and all the Valencia orange crop. Some small-scale farmers without crop insurance are turning to online donation appeals.

Drought in the U.S. Southwest is taking a toll on ranches and farms in New Mexico, Arizona, Utah, and Colorado. As ponds dry up, ranchers in southern Utah spend hours each day hauling water to thirsty herds. The five main reservoirs on the Rio Grande and Chama Rivers that serve New Mexico and Arizona were at a combined 7 percent capacity in early March, 10 percent lower than the drought in 2018. Fourteen New Mexico counties have received drought disaster declarations, opening up eligibility for emergency loans. Bark beetle infestations are on the rise due to drought, threatening Santa Fe’s piñon trees.

A heavy snow storm in mid-March dumped up to three feet of snow in parts of Colorado and Wyoming, cutting power to 30,000 people. The Colorado National Guard was activated, nearly 1,950 flights were canceled at Denver International Airport, and bus and rail transport were delayed.

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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