Climate Change: Historic Drought Projected to Persist, Worsened by Thin Western Snowpack
- Feb 25, 2013 2:30 am GMT
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Time is running out to avert a third summer of drought in much of the High Plains, West and Southwest, federal officials warned Thursday.
Without repeated, significant bouts of heavy snow and rain in the remaining days of winter, a large part of the country will face serious water supply shortages this spring and summer, when temperatures are hotter and average precipitation is normally low.
The drought already ranks as the worst, in terms of severity and geographic extent, since the 1950s. Though it’s not over yet, its economic impact appears to be severe, said Brad Rippey, a meteorologist at the Agriculture Department’s Office of the Chief Economist.
It “will probably end up being a top-five disaster event” on the government’s ranking of the costliest weather events of the past three decades, he said at a Capitol Hill briefing Thursday.
There is little relief predicted in the National Oceanic and Atmospheric Administration’s (NOAA) latest three-month drought outlook, which the agency released Thursday. Federal forecasters predict that drought will persist in the Rocky Mountain and Plains states, expand throughout northern and southern California and return to most of Texas, a state that has been mired in drought since 2011.
NOAA does forecast improvements in drought conditions in the Upper Midwest and Southeast, areas that have received beneficial precipitation in recent weeks.
“The next couple of months will kind of determine how the spring and summer plays out in that part of the country,” said Jake Crouch, a climate scientist at NOAA’s National Climatic Data Center in Asheville, N.C. Crouch said that continued drought conditions could threaten water supplies in many areas, particularly in the Southwest.
Dwindling Water Supplies
With drought extending into its second or even third year in some areas, the main concerns are shifting from agriculture and recreation to water supplies as rivers run dry and reservoirs shrink.
Speaking at the annual meeting of the American Association for the Advancement of Science in Boston on Feb. 15, Texas state climatologist John Nielsen-Gammon said water managers are especially concerned about the situation in West Texas, where emergency conservation plans have gone into effect as water supplies dwindle.
In the western U.S., low mountain snowpack is once again a concern, especially in portions of Colorado, New Mexico and Wyoming that feed the Platte and Arkansas rivers, said Mike Strobel of USDA’s National Resources Conservation Service.
“We’ve got the same trend we had last year,” Strobel said. “But prior to last year, we had very good snowpack, so there was a lot of moisture in reservoirs and soil” when drought conditions hit. This year, reservoirs are running low and soils are dry, which could magnify the impact of a winter without much snow buildup.
In Colorado, where 100 percent of the state is experiencing some level of drought, snowpack is at 70 percent of the long-term average and just 91 percent of last year’s total, Strobel said. Streamflow forecasts are poor and reservoir levels are low.
“We just don’t have the water in storage right now as we’re heading into the spring and summer, periods that are essential for agriculture and water management,” he said.
“We need rain in spring and fall so that we don’t have a crisis like we had this year on the Mississippi,” said Steve Buan from NOAA’s North Central River Forecast Center.
The portions of Minnesota, Wisconsin and Iowa that funnel water into the Mississippi are “bone dry,” Buan said. NOAA estimates there is a 40 percent chance that come fall of 2013, the Mississippi River will dip as low, or lower, than during the record-breaking autumn last year.
The drought was most likely initially set into motion by the cooler-than-average water temperatures in the tropical Pacific Ocean, combined with the effects of warmer-than-average waters in the Atlantic Ocean. Studies have shown that this combination tends to favor major drought events in the U.S.
But some scientists, such as Nielsen-Gammon, suggest that the overall warmer climate created by manmade global warming may have amplified this already devastating drought, particularly by triggering more intense heat during the spring and summer of 2012.
A recently released draft of a new federal climate change assessment shows that as the climate continues to warm in the next few decades, drought events are likely to become more frequent and severe, leading to more significant water supply and agricultural impacts in much of the U.S
The continuing drought has already taken a toll on the nation’s farmers, said the USDA’s Rippey.
Drought during last year’s growing season took “major hits on row crops,” especially corn and sorghum, he said. Parched conditions reduced the nation’s production potential for those two crops by about one-quarter. Drought cut corn yields by 4 billion bushels and sorghum yields by 100 million bushels.
According to Climate Central research released on Feb. 18, the states of Missouri, Illinois and Indiana were among the hardest hit “Corn Belt” states, with yields at nearly 30-year lows.
The U.S. soybean crop rebounded slightly during a cooler, wetter August last year, though the overall yield still dropped by 200 million bushels, USDA found.
But heading into spring, it’s winter wheat that is the most immediate concern, Rippey said. In Oklahoma and South Dakota, roughly two-thirds of the current winter wheat crop is rated “poor” or “very poor,” while more than half of Texas’ crop falls into the same categories despite some rainfall this winter.
“We are at high risk for abandonment this year,” Rippey said, predicting that farmers could walk away from 25 percent or more of the nation’s winter wheat this year, the worst since 2002, unless their crops begin receiving steady, regular rains.
USDA won’t release its official estimates of crop production for 2013 until mid-May. But the agency is optimistic that U.S. corn will do well this year, yielding 163.5 bushels per acre. July weather will tell the tale, Rippey said, but encouraging signs include ebbing drought in the eastern half of the Corn Belt.
Another Destructive Wildfire Season Ahead?
It’s still too early to tell whether poor snowpack and persistent drought will yield another severe fire season in the western U.S., experts said.
Last year’s fires consumed many of the dead and damaged trees and underbrush that fuel wildfires, said Jim Douglas, a senior advisor at the Interior Department.
“If that fuel doesn’t regrow, it’s not there,” he said. “So we could have drought conditions with nothing to burn yet. And we could have a spring with early moisture, with a lot of grass growing good and tall. If it dries out in late summer, we could have very bad fire conditions.”
The National Interagency Fire Center projects an immediate above-average fire risk in regions hardest hit by drought in its Feb. 1 outlook, including portions of the Oklahoma Panhandle and eastern Colorado. But in the drought-stricken Rocky Mountains and Southwest, fire season normally doesn’t begin until April, the center said, and what it will look like isn’t yet clear.