CHEYENNE (AP) — Water runoff forecasts for the upper North Platte River and its tributaries in the months ahead keep getting worse with each week that passes without a big mountain snowstorm.
A February runoff forecast prompted the Wyoming State Engineer’s Office to issue its first wintertime call on water rights for Wyoming’s portion of the North Platte drainage in eight years.
The forecast predicted total runoff of 705,000 acre-feet of water, well within the 1.1 million acre-foot trigger for a call on priority administration of water rights. An acre-foot is enough water to cover an acre of ground a foot deep. The call remains in effect.
The latest snowmelt forecast this week predicts even less runoff: 615,000 acre-feet. Each forecast tends to be more accurate as existing snow melts and less new snow accumulates.
“Every cloudy day helps, one more day that snowpack’s going to stay on the hill,” Matt Hoobler, North Platte River coordinator for the State Engineer’s Office, said Thursday.
At this rate, calls on water rights for the Wyoming portion of the river system appear likely to continue for some time. That would affect many farmers and ranchers in southeast Wyoming who use surface water for irrigation.
Each May, water rights rules that apply to irrigators take effect under an agreement between Wyoming and Nebraska that governs use of North Platte River water.
If the drought continues, farmers and ranchers who own the oldest water rights would have priority to use North Platte water and connected water sources before owners of younger water rights. Those with junior water rights would have to buy water from or make other arrangements with senior rights holders.
The scarcity begins high above the flat country where the North Platte flows wide.
Snow depths remain well below average in the Medicine Bow, Sierra Madre and Laramie mountains of Colorado and southern Wyoming that feed water into the North Platte system. Hoobler said he saw it firsthand, recently snowshoeing in the backcountry to check snow depth gauges.
“The top 8 inches to 14 inches has some wonderful moisture in it,” he said.
Below that, he said, is about 2 feet of grainy, icy snow that contains less moisture but can absorb water like a sponge.
“Once we get down through that wet stuff — if that melts off, melts down through, or evaps away — it won’t be long until that other snow disappears,” Hoobler said.
Snowpack moisture is well below average in three North Platte tributaries: About 76 percent of normal in the Little Laramie River drainage, 77 percent in the Laramie River drainage, and 81 percent in the Medicine Bow River drainage, he said.
He said little snow remains and might be gone by the end of April at some low-elevation gauges.