Wyoming maintains average waterWritten by Natasha Wheeler
“We are holding our own here, right in the middle of a wet year and dry year,” remarks Hydrologist Jim Fahey of the Wyoming National Oceanic and Atmospheric Administration (NOAA).
In his latest bulletin, the February 2015 Wyoming Water Supply Outlook and Graphic dated Feb. 9, he notes that current water year precipitation is averaging near 95 percent of normal in Wyoming. January precipitation totals were near 70 percent of normal, varying across the state from 119 percent in the Bighorn Basin to 32 percent in the Little Snake Drainage.
NOAA indicates that the Bighorn Basin, Powder River Basin and Belle Fourche Basin were the only areas in the state that are currently above 90 percent of normal precipitation, according to Jan. 2015 data.
As of Feb. 3, the National Drought Mitigation Center illustrated only a small portion of Wyoming under any drought-type condition. The central-southern portion was noted as abnormally dry.
“January and February are usually pretty dry,” notes Fahey in reference to precipitation. “Our wet season runs through March, April and May.”
A look back
In January’s report, spring snowmelt flood potential remains low to moderate throughout the state. In the seven-day period from Feb. 4-10, NOAA reported snowfall across the state anywhere from zero to nine inches, with the most snowfall in Teton and Platte counties.
“Statewide water levels are a little below average,” Fahey explains.
Rivers in the northwestern part of the state are running at nearly 91 to 105 percent of average water supply, whereas water supply in the southeast corner is currently less than 75 percent.
“Levels are about normal west of the divide and a little behind east of the divide, but we are still coming up to the wet season,” he says.
Mountain snowpack, recorded at the beginning of February, sits at 90 to 95 percent of normal. Snowpack in December 2014 was at 107 percent of the average. The highest of snow water equivalent (SWE) at the beginning of February was recorded in the basins of northern Wyoming, varying from 105 to 125 percent of normal.
“The recent warm spell has melted some of the low-station snow, but it hasn’t done much to the mountain snowpack,” he says. “We had quite a bit of snow in Big Horn, Hot Springs, Thermopolis and Worland, for example, but there is now less than six inches of snowpack in those places.”
Every state in the lower 48 had above-average December temperatures in 2014. Laramie tied for its second-warmest December temperature, with records going back to 1948 on Dec. 12, but also tied for its second-coldest temperature on Dec. 31. There was a 94-degree range between those two temperatures, from 60 degrees to -34 degrees, respectively, according to NOAA.
Stream-flow volumes from snowmelt for the 2014-15 water year are currently predicted to be below average, estimated at 85 to 95 percent of normal. Volumes are expected to be slightly above average for the year across the Yellowstone/Clarks Fork and the Powder River Drainage.
Stream-flow levels below average are predicted for southern drainages, including the Sweetwater, Little Snake, North Platte, Laramie and Bear drainages.
“We have lost a lot of the ice in the rivers this year, which is good as it may mean less ice jamming this year,” Fahey comments.
As spring runoff approaches, he mentions that water levels from last year have aided in a positive water report this winter. Statewide reservoir storage is greater than 115 percent above average for February so far this year.
“We have pretty good carryover from all of the major reservoirs,” Fahey explains.
The first of October marks the beginning of the recorded water year, and the 2013-14 water year had high precipitation through the summer and the early fall, contributing to this year’s reservoir levels.
NOAA indicates that statewide total precipitation in August 2014 was 2.38 inches, 1.31 inches above the baseline value by a 100-year average from 1901 to 2000.
“Total precipitation levels last year were a little above normal for most of the state,” he adds.
From May 11-13, 2014, a late-season snowstorm brought over 40 inches of snow to some parts of Wyoming. In Cheyenne, 12 inches of snow fell, creating a record for the heaviest single-day snowfall for the city, that late in the season. Warm weather conditions returned to the state shortly after the storm.
2011 was an above-average year, followed by a few dry years, with much more promising levels of precipitation in the summer and early fall of the last two years.
“It is a little early still to forecast this year’s water supply,” Fahey says.
The baselines for precipitation in May and June are 2.21 inches and 1.84 inches, respectively, according to NOAA. That is in contrast to 1.06 inches in January and 0.97 inches in February, for baseline precipitation.
“What will make or break us in Wyoming is always the rain in the spring,” comments Fahey.