The Big Picture
Though much of the 12-month map (below) is colored, indicating water conditions other than normal, most parts of the country do not exceed moderate anomalies (5 to 10 year expected frequency). However, more severe water deficits are evident in much of southern California, southwestern Arizona, southern Pennsylvania, parts of Alaska, and in a few other pockets across the nation. Water surpluses that are severe (10 to 20 years) to exceptional (greater than 40 years) are noticeable in northeastern Nevada and across the border into Idaho, eastern Texas, parts of Nebraska, scattered pockets in the Northwest, south-central Alaska, and the western half of the island of Hawaii.

Flooding in the Houston area has claimed at least seven lives, flooded 1,000 homes, and caused more than $5 billion in damage. The governor declared a disaster in nine counties and emergency crews made more than 1,200 high-water rescues. Over 123,000 homes lost power. Flooding on the Colorado River in Wharton, Texas, 60 miles southwest of Houston, forced residents of some neighborhoods to evacuate as several feet of water swirled through homes.

Earlier flooding in March along the Sabine River in Texas washed oil and fracking chemicals into the river as it inundated oil wells and fracking sites. 

In Norman, Oklahoma storms flooded the streets and in Lawton cars were submerged in the mall parking lot and children were stranded on park picnic tables and playground equipment. City plows had to be called in to remove hail accumulation of four to five inches on Interstate 680 in Omaha, Nebraska.  

The US Drought Monitor reports that conditions in Northern California have improved, but much of Southern California remains in severe to exceptional drought.

On Wednesday May 18th Lake Mead hit its lowest level since the man-made reservoir was created by the building of the Hoover Dam in 1935.

Forecast Breakdown
Comparing the observed conditions February through April with conditions forecast for May through July, as seen in the 3-month maps below, the emergence of water deficits in the Northeast, East Coast, and Upper Midwest is clear. Moderate (5 to 10 year expected frequency) to extreme (20 to 40 years) deficits will emerge along much of the Eastern Seaboard with greatest severity in the Northeast; deficits in Tennessee and the Virginias will become less severe. Deficits primarily in the abnormal (3 to 5 years) to moderate (5 to 10 years) range will emerge throughout the Upper Midwest and in northern portions of Illinois and Indiana. The forecast for Michigan’s Upper Peninsula indicates more severe water deficits than in surrounding regions. Deficits will persist in Southern California and Arizona.

Surpluses will continue to emerge May through July in: Idaho and northeastern Nevada; a large block of eastern Texas; between Amarillo and Lubbock; and near Mt. Livermore in western Texas.

Though some blue/green areas show on the August through October map – northeastern Nevada, southern Idaho, eastern Texas – indicating the persistence of water surplus, the transition to more areas of deficit is evident. Though most areas of emerging deficit are mild, deficits along the Missouri and Yellowstone Rivers, which trace an orange path through the Missouri Basin, are expected to be moderate to severe, as are the emerging deficits in northwestern Wyoming. Deficits in Southern California are expected to increase in severity during this period.

The forecast for the final quarter of the forecast period (Nov 2016-Jan 2017) shows much of the country in mild water deficit conditions along with the emergence of scattered surpluses.

Outside the contiguous US, water surpluses are forecast for south-central Alaska from Bristol Bay northward through September, surrounded by deficits of varying severity throughout much of the state which diminish in the fall. Moderate surpluses are in the forecast for the west end of the island of Hawai’i for much of the forecast period.

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


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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