United States: Water deficits to persist in the Pacific NW

17 August 2021

THE BIG PICTURE
The 12-month forecast ending April 2022 indicates widespread water deficits of varying intensity in the U.S. West, Pacific Northwest, Rocky Mountains, and Northern Plains. Deficits will be exceptional in many areas but particularly dominant in Northern California, Oregon, and North Dakota. Deficits on the Colorado River will be moderate.

In Minnesota’s northern half, anomalies will be severe overall, becoming more intense in the Red River Basin in the northwest and somewhat less intense in the state’s southern half and into northern Iowa. Deficits are also forecast for Wisconsin’s northern and southern extremes and Michigan’s Upper Peninsula.

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In the U.S. Northeast, the northern reaches of New York, Vermont, and New Hampshire can expect deficits of varying intensity while some moderate surpluses are forecast in their southern regions and into Massachusetts and Connecticut. Much of Maine will experience moderate to extreme deficits. In Peninsular Florida, moderate to severe deficits are forecast around Lake George in the north and around Lake Okeechobee in the south.

Surpluses will be widespread in the Gulf States of Louisiana and Mississippi reaching into neighboring Alabama and Texas and north through parts of Arkansas, Oklahoma, Missouri, Kansas, and Illinois. Anomalies will be moderate overall but severe to exceptional in southern Louisiana and exceptional in coastal Mississippi. Texas can also expect surpluses along a stretch of its coast from the Brazos River to Corpus Christi and following the Canadian River in the Panhandle.

Nearby, surpluses will follow the Upper Canadian River region in New Mexico and reach into a pocket of south-central Colorado. Surpluses are also forecast along the South Fork Republican River near Nebraska’s southwestern border leading into Colorado and in a pocket of north-central Kansas.

Outside the contiguous U.S., Alaska can expect widespread exceptional deficits in the northeast, deficits near Anchorage and Valdez in the south, and deficits in the center of the state between the Yukon and Kuskokwim Rivers. Areas with a forecast of surplus include Juneau, around Iliamna Lake, and the central Arctic Coast.

Most of the Hawaiian Islands will experience surpluses but moderate deficits are expected in Maui. Moderate to severe deficits are forecast for Puerto Rico.

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

The forecast through October indicates that deficits will shrink and downgrade, but anomalies will remain widespread in Northern California, the Pacific Northwest, the Rockies, and Northern Plains. Widespread exceptional deficits will persist in western Oregon and the Salmon River Basin in Idaho but exceptional deficits in North Dakota will downgrade. Severe deficits will trace the Missouri River through the Dakotas to Omaha. Normal conditions will return to many areas of Nevada, Utah, Wyoming, South Dakota, and Arizona, and some surpluses will emerge in southern Nevada and from Phoenix to Arizona’s eastern border. In the U.S. East, deficits will downgrade in Maine and from eastern Ohio through the Appalachians into Maryland. Moderate surpluses will emerge in New York and southern New England, and in pockets from coastal Virginia through the southeastern states and Florida’s Gulf Coast. Surpluses will remain widespread in Mississippi, Alabama, and southern Louisiana and will be intense in Mississippi. Some surpluses will linger in Oklahoma, eastern Texas, and from the Brazos River to Corpus Christie, and will intensify on the Canadian River through the Panhandle, becoming severe. Other areas of surplus include the Canadian River through New Mexico and the nearby region in Colorado, the Republican River, and the northern reaches of Michigan’s Lower Peninsula.

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From November 2021 through January 2022, deficits are expected in the northern Rockies, along the Missouri River in Montana, the northern half of Minnesota, and pockets in Iowa. Anomalies will be exceptional in Idaho and severe to extreme in Minnesota. Surpluses will emerge in Michigan, Wisconsin, and from northeastern Missouri though Illinois, Indiana, Ohio, and parts of Upstate New York. Surpluses are also forecast in pockets of the Central Plains and Southwest.

The forecast for the final months – February through April 2022 – indicates persistent deficits in Minnesota and emerging deficits in southeastern New Mexico. Surpluses are forecast in the Great Lakes region and beyond, and in pockets from the Pacific Northwest through the Rockies and Central Plains.

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

IMPACTS
Lake Mead, by volume the largest reservoir in the U.S., has dropped to its lowest level since first being filled in the 1930’s. Flows on the Colorado River that feed the lake have been so low due to drought that for the first time ever the federal government has declared a water shortage, a declaration that will reduce water allocations to Nevada, Arizona, California, and Mexico beginning January 1.

In early August, drought and heat forced California’s Oroville Dam power plant to shut down for the first time in its history.

Water managers in Idaho are warning that the state’s current drought could stretch on for years. Though last winter’s snowpack was considered normal, a dry spring and unusually high summer temperatures - record-breaking in June and July - left reservoirs low and experts say it could take several years for water inventory to replenish.

The Dixie Fire, one of six large blazes in Northern California, has raced through the Sierra Nevada foothills with flames currently licking through 600,000 acres aided by high winds, high temperatures, and dry conditions. The U.S. Forest Service has deployed 21,000 federal firefighters to battle multiple fires in the West including the Monument Fire, the McFarland Fire, and Oregon’s Bootleg Fire.

Torrential downpours have caused flooding and landslides in several parts of the U.S. over the past month.

During the last weekend in July, the Glenwood Canyon region in Colorado received more rain in five days than is normal for the entire month, triggering a mudslide that damaged portions of I-70 west of Denver. Burn scars from last year’s fire season have left some areas of the state particularly susceptible to flooding and landslides, said the governor.

Severe storms cancelled hundreds of flights a Chicago’s O’Hare Airport and prompted evacuation of the control towers.

Flash flooding in Omaha, Nebraska sent cars floating down the street and left several people fighting to get out of an elevator as it filled with water.

Multiple storms in Michigan left nearly 839,000 without power, many for several days in the midst of a heatwave.

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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