United States: Intense water surpluses will persist in KS, NE, IA, OK, TX

20 March 2019

THE BIG PICTURE
The 12-month forecast ending November 2019 indicates that water surpluses of varying intensity will affect many parts of the conterminous U.S. Primarily moderate to severe surpluses are forecast in a broad path down the center of the country from the southern portions of Minnesota and Wisconsin through the central Plains and Mississippi River states and most of Texas to the Gulf of Mexico. Surpluses will be extreme to exceptional in central Kansas and the northern Edwards Plateau in Texas around Abilene, and extreme along the Lower Mississippi River. Surpluses will also be widespread south of the Ohio River through northern Florida and will be intense in eastern Tennessee, northern Alabama, and northern Georgia. In the western half of the U.S., surpluses are forecast in California, the northern Rockies, Nevada, Utah, northern Arizona, Colorado, and along many rivers.

Back East, conditions of both deficit and surplus are forecast for the northern Ohio River Basin and from New Jersey through South Carolina.

Primarily moderate deficits are expected in western Oregon, Washington, northern Minnesota and pockets of North Dakota.

Outside the contiguous U.S., in Hawaii surpluses are forecast for western Hawai’i, Moloka’i, and Lana’i, and moderate deficits on Maui. In Alaska, surpluses are forecast on the Alaska Peninsula reaching inland; southeast of Barrow in the far north; and along the Upper Koyukuk and central Yukon Rivers. Deficits are expected in the Seward Peninsula and into western Alaska; along the Tanana River through Fairbanks; around Anchorage; and in the Alaska Panhandle. Severe deficits are forecast for Puerto Rico.

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

Most notable in the forecast for March through May is the absence of widespread, intense surpluses observed in the East in prior months, and the emergence of surpluses in the West.

In the center of the country, surpluses will shrink and downgrade but remain widespread in a broad path that includes southern Minnesota, southeastern Wisconsin, Iowa, Nebraska, Kansas, northern Missouri, Oklahoma, Arkansas, Louisiana, and parts of Texas. Surpluses will be especially intense in Kansas and in Texas in the northern Edwards Plateau. Moderate deficits are forecast for northern Minnesota.

In the West, Colorado will transition from deficit to intense surplus as will Idaho, Nevada, and northwestern and eastern Utah. Moderate surpluses will increase in California, covering much of the state. Other areas of surplus include northern Arizona and pockets of central Oregon. Deficits are forecast for Washington, pockets of Oregon and the Northern Rockies, and in northern Wyoming.

Surpluses are forecast along many rivers, with exceptional surpluses along the Arkansas River from Kansas into Colorado and the Snake River in Idaho; extreme surpluses on the San Juan River through New Mexico, Colorado, and Arizona; and moderate to severe surpluses on the Mississippi, the Missouri, the Canadian, and North Platte Rivers.

In the East, moderate surpluses are forecast for Virginia, Tennessee, northern North Carolina, northeastern Mississippi, northern Alabama, and small pockets in the Northeast, including New York and northern New Hampshire. Intense deficits will persist in northern New York. Regions with a forecast of less intense deficit include Maine, Vermont, Pennsylvania, Connecticut, New Jersey, West Virginia, and southern Florida.

From June through August, surpluses in the center of the country and the West will diminish but persist, and exceptional deficits will nearly disappear. Primarily moderate surpluses are forecast for southern Minnesota, southern Wisconsin, southeastern South Dakota, Iowa, eastern Nebraska, Kansas, northern Missouri, Oklahoma, west-central and south-east Texas and southern Louisiana. Severe surpluses will emerge on the Pecos River in western Texas. Moderate to severe deficits will persist in Oregon and Washington. Primarily moderate deficits will emerge in the northern Ohio River Basin reaching the Mid-Atlantic States, and severe deficits in eastern North Carolina. Moderate surpluses will emerge in Florida.

The forecast for the final months – September through November – indicates moderate surpluses down the center of the country, in the Deep South, pockets throughout the West, and along many rivers. Moderate deficits are forecast for the Pacific Northwest, northern Wisconsin, pockets of the northern Ohio River Basin, and Maine.

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

IMPACTS
Up to 20 inches of rain fell across northern California in late February causing the Russian River to reach its highest levels in 25 years, resulting in major flooding. The state’s governor declared a state of emergency in Sonoma, Lake, Amador, Glenn, and Mendocino Counties. Dozens of people were rescued, at least one person was killed, and over 2,600 buildings were damaged.

The same atmospheric rivers inundating northern California with heavy rains also contributed to this winter’s 37-plus feet of snowpack in the Sierra Nevada mountain range, set to replenish depleted California groundwater levels that have plummeted over a long-term drought in the last several years.

A major snowstorm dropped 40.3 inches of snow on Flagstaff, Arizona over the course of two days, and the 35.9 inches that fell in one of those days broke the record for daily snowfall in the city. The storm system shut down travel over the mountains of Arizona, New Mexico, and southwestern Colorado. Snowy, frigid conditions closed schools in Las Vegas, which hasn’t seen measurable snowfall since 2009.

A heavy rain system brought several rivers across the lower Mississippi, Tennessee, and lower Ohio River valleys to flood stages last month. City and county officials in Grenada, Mississippi declared a local state of emergency when dozens of streets and homes were flooded. The governor of Alabama declared a state of emergency for 19 counties after the ground in the northern part of the state became saturated. Nashville, TN reported its wettest February on record even before the storm system reached it, and nearly 100 roads were closed due to flooding in Knoxville. Interstate 40 in North Carolina was closed near the Tennessee state border due to a rock slide.

The governor of Puerto Rico braced its residents for water rationing last month, as 76 percent of the island is experiencing abnormally dry conditions while an additional 8 percent is suffering a moderate 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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Many analyses reported in ISciences-authored blog posts are based on data generated by the ISciences Water Security Indicator Model (WSIM). Other sources, if used, are referenced in footnotes accompanying individual posts. WSIM is a validated capability that produces monthly reports on current and forecast global freshwater surpluses and deficits with lead times of 1-9 months at 0.5°x0.5° resolution. This capability has been in continuous operation since April 2011 and has proven to provide reliable forecasts of emerging water security concerns in that time-frame. WSIM has the ability to assess the impacts of water anomalies on people, agriculture, and electricity generation. Detailed data, customized visualizations, and reports are available for purchase.

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