Thursday, March 22, 2018

National Drought Mitigation Center

December 2015 Drought and Impact Summary

Drought and Climate for December 2015: Heavy rains erode drought in the Northwest

Access the latest monthly drought outlook from NOAA's Climate Prediction Center.

The two maps above are from the High Plains Regional Climate Center.

Find these and other products related to the U.S. Drought Monitor on the USDM website.

By Brian Fuchs, NDMC Climatologist


December brought with it continued improvement and elimination of drought in many locations. Drought was affecting 18.74 percent of the contiguous United States on Dec. 29, 2015, compared to 20.58 percent on Dec. 1. Severe drought improved from 14.68 to 11.56 percent, extreme drought improved from 8.34 to 6.28 percent and exceptional drought remained unchanged. The western United States was still in the grips of a multi-year drought.  Approximately 75.2 million people were in drought-affected areas at the end of the month, compared to approximately 77.8 million people at the beginning. A year earlier, at the end of 2014, 28.68 percent of the contiguous United States was in drought, affecting a population of more than 66 million people.

Drought Outlook

Some improvements to the western drought are anticipated in January, especially along the coast. Improvement is also possible in Arizona and in New England. Drought may develop in Wyoming and Montana. Hawaii may also see more drought developing, while drought will persist in Puerto Rico.


December was warmer than normal, by as much as 10-12 degrees, over many of the areas east of the Missouri River Basin. Temperatures that were 3-5 degrees cooler than normal prevailed over much of the Great Basin and the southwestern United States.


Much of the country was wet in December, with some areas of Oklahoma, Texas, Alabama, Georgia, Oregon, Washington and northern California receiving 10-12 inches more than normal for the month. But portions of the Southeast and Southwest were up to 3 inches drier than normal.


Regional Overviews


Lingering, long-term drought remained in portions of New England. The area in drought increased slightly in December from 6.39 to 6.60 percent of the Northeast region. Temperatures were 10-12 degrees warmer than normal in December throughout the Northeast. Precipitation was above normal for most areas, but with a “snow drought,” as most precipitation has been liquid.


A wetter-than-normal pattern kept the Southeast drought-free in December. Temperatures were warm for December, with departures of 9-11 degrees above normal common throughout the Southeast. Most areas were also above normal for precipitation, with portions of Alabama and Georgia 9-11 inches wetter than usual for the month. Coastal regions from South Carolina to Florida were up to 3 inches drier than normal.

Movers & Shakers for December 2015

Percent area
Dec. 1, 2015
Percent area
Dec. 29, 2015
Status Percentage point change

Biggest increases in drought
0.00 3.83 moderate 3.83
Rhode Island
15.21 18.42 moderate 3.21
Wyoming 0.09 4.25 moderate 4.16
Biggest improvements in drought
California 92.26 87.55 severe 4.71
Idaho 67.45 64.05 moderate 3.40
42.15 24.35 severe 17.80
8.38 1.18 extreme 7.20
Indiana 18.07 10.41 moderate 7.66
Kansas 4.51 0.00 moderate 4.51
Michigan 15.85
10.93 moderate 4.92
Montana 26.06 20.95 severe 5.11
New Jersey
17.64 7.08 moderate 10.56
North Dakota
9.27 5.47 moderate 3.80
Oregon 96.01 80.45 moderate 15.56
90.37 65.33 severe 25.04
60.62 39.55 extreme 21.07
Washington 64.49 25.67 moderate 38.82
60.38 2.72
severe 57.66
44.51 0.00 extreme 44.51


Drought was minimal in the Midwest in December with only 2.35 percent of the region in drought at the end of the month compared to 3.16 percent at the beginning of the month. Much of the dryness was confined to portions of Michigan, Indiana and Ohio. All of the Midwest was normal to above normal for precipitation in December, with portions of Missouri, Iowa and Illinois 4-8 inches wetter than usual. The Midwest was also warmer than normal for December, by as much as 6-10 degrees in many areas.

High Plains

Most of the High Plains was drought-free at the end of December, with only 1.58 percent of the region in drought, compared to 2.03 percent at the beginning of the month. Most of the High Plains was warm, with many areas recording temperatures 3-6 degrees above normal, although portions of western Nebraska and western South Dakota were as much as 3 degrees cooler than normal. Most of the High Plains was up to 4 inches wetter than usual for December.


The South remained wet through December with no drought in the region. Flooding rains in portions of northeast Texas, eastern Oklahoma and Arkansas led to many locations having record wet years for 2015. Generally, the South was 3-6 inches wetter than normal for December precipitation. In most areas of the South, temperatures were 3-6 degrees warmer than normal.


Above-normal precipitation for December shrank drought in the West. December ended with 45.07 percent of the West in drought, compared to 48.88 percent at the beginning of the month. Severe drought improved from 37.23 to 29.30 percent of the West, extreme drought improved from 21.16 to 15.92 percent, and exceptional drought remained unchanged. Temperatures were 2-4 degrees warmer than normal in the Pacific Northwest, and 2-4 degrees cooler than normal in much of the Southwest. The coastal region of Oregon and Washington received 9-12 inches more than normal precipitation. Areas of the Southwest and southern California were as much as 3 inches drier than normal.


December 2015 impact summary: California fine-tunes regulations; Central Valley contending with land subsidence and uranium contamination

The two charts above summarize information from the Drought Impact Reporter.

The two charts above summarize information from the California Department of Water Resources Water Conditions page.

By Denise Gutzmer, NDMC Drought Impact Specialist

Forty-five drought impacts were logged in the Drought Impact Reporter in December, with most of those documenting events in California, the epicenter of the Western drought. While Californians continued to conserve water, long-awaited El Niño storms started pounding the state in early January, dropping too much rain too quickly and bringing rivers back to life.

Anticipated El Niño may have reduced conservation

Although Californians complied with Gov. Jerry Brown’s order to conserve 25 percent of water used starting in June, conservation slowed a bit in October and November, ahead of the anticipated El Niño storms. Conservation slid to 22 percent and 20 percent in October and November, slightly below the governor’s mandate, but the state was still on track to save at least 25 percent of water typically used between June 2015 and February 2016, a significant achievement.

“California misses mark for saving water 2 months running,” by Scott Smith, Associated Press, KPCC (Pasadena, Calif.), Jan. 5, 2016

Regulators considering proposed adjustments to conservation mandates

Water conservation mandates, requiring a cut of as much as 36 percent of water consumption compared to the baseline year of 2013, have been a source of consternation for water agencies striving to meet the strict conservation targets set forth by the State Water Resources Control Board. Many cities and agencies have complained that the mandates do not take into account their specific circumstances or population changes, and hope for at least a little leeway. California water regulators proposed easing water conservation targets, particularly for communities that have lost trees for lack of water and for communities that have developed alternative water supplies, such as those with water recycling or desalination plants. Regulators were considering easing mandates by up to 4 percentage points.

“Felicia Marcus: CA likely to tweak drought mandate,” by Sammy Roth, Palm Springs Desert Sun (Calif.), Dec. 3, 2015

“Water agencies want relief from conservation regulations,” by Amy Quinton, Capital Public Radio (Sacramento, Calif.), Dec. 7, 2015

“State might ease targets for cutting water use in some Orange County cities,” by Aaron Orlowski, Orange County Register (Santa Ana, Calif.), Dec. 21, 2015

First snow survey brings good news; El Niño brings too much of a good thing

The first media snow survey for the 2015-16 season on Dec. 30 turned up 16.3 inches of snow, amounting to about 136 percent of the historical average for Echo Summit. While the above-normal snowfall was very welcome, the state’s two largest reservoirs, Shasta and Oroville, held about one-third of normal December storage. Despite the plentiful precipitation expected in California this winter, not enough rainfall is expected to end the drought.

With the start of the new year, a series of El Niño-fueled storms began bringing torrents of rain, leading to flash flooding and landslides. The public has been warned to prepare for drenching rainfall by clearing debris and sandbagging as needed. Homeless encampments were mapped and shelters set up to accommodate 6,000 beds.

“California drought: Snowpack at Echo Summit is 136 percent of normal,” by Lisa M. Krieger, San Jose Mercury News (Calif.), Dec. 30, 2015

“Record-Tying El Niño's Storms Hitting Parched California,” by Kristin J. Bender and Scott Smith, Associated Press, ABC News, Jan. 5, 2016

Groundwater pumping leads to sinking land in the Central Valley

Land subsidence in the Central Valley, which accelerated in the past four years of drought as groundwater pumping increased, has damaged bridges and canals, at an estimated cost of billions of dollars. Groundwater comprises 40 percent of water used in a wet year, but during drought, can provide up to 65 percent. Decades of heavy pumping have buckled canal linings, forcing irrigation districts to raise the canal sides to keep water flowing. The cost of rebuilding one canal came to $4.5 million, while the expense of rebuilding a Los Banos bridge was put at $2.5 million. Some areas have subsided more than a foot in less than a year.

“Damage from sinking land costing California billions,” by Scott Smith, The Associated Press, The Santa Rosa Press Democrat, Dec. 27, 2015

Uranium contamination a growing threat in the Central Valley

An increasing number of wells in California’s Central Valley were contaminated with uranium, threatening the health of those who consume the water. About 25 percent of families using private wells in the Central Valley were consuming water containing dangerous amounts of uranium. Up to 10 percent of public water systems use raw water that contains more uranium than is allowed by government safety standards. The average amount of uranium in the public-supply wells in the eastern San Joaquin Valley increased 17 percent from 1990 to the mid-2000s, according to the U.S. Geological Survey. Long-term uranium exposure can damage kidneys, increase cancer risks and cause other problems.

Uranium enters the water supply when snowmelt picks up uranium-laden sediment, which is carried downstream to cropland. Crops produce a weak acid that draws uranium from the sediment and contaminates the water.  As wells are used, the contaminated water is drawn down into the ground where it eventually is pumped for use as drinking water. Drought has intensified the problem as groundwater is over pumped to compensate for the lack of rain.

“Fear at the tap: Uranium contaminates water in the West,” by Ellen Knickmeyer and Scott Smith, Associated Press, San Francisco Chronicle, Dec. 8, 2015

Big desalination plant open in Carlsbad, California

The largest desalination plant in the Western Hemisphere had its ceremonial opening in Carlsbad on Dec. 14 and began commercial operations later in the month. The plant produces 50 million gallons of fresh water daily, providing 7 to 10 percent of San Diego County Water Authority’s needs and protecting the region against water supply shortages.

“Carlsbad desalination plant will help ease water crunch, but price is steep,” by Dale Kasler, Orange County Register (Santa Ana, Calif.), Dec. 14, 2015

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