Going into March, typically the heaviest snow month in the Greater Yellowstone Ecosystem, snow water equivalent reports are close to 30-year medians.

According the Natural Resources Conservation Service State Soil Scientist Jeff Goats, the snow water equivalent across Wyoming for March 1 was at 117% of median. The Little Snake River Basin recorded the highest at 148% of median and lowest for the South Platte River Basin at 95% of median.

Reservoir storage was 88% of median across the entire state. Reservoirs in the Wind River Basin are near median at 98%. Reservoirs on the Bighorn are slightly below median at 95%. The Buffalo Bill Reservoir on the Shoshone is near median at 105%.

Yields from the Wind and Big Horn river basins should be about 112% and 109% of median respectively. Yields from the Shoshone River Basin should be 97% of median.

Most of the annual streamflow in the western United States originates as snowfall that has accumulated in the mountains during the winter and early spring. As the snowpack accumulates, hydrologists estimate the runoff that will occur when it melts. Measurements of snow water equivalent at selected manual snow courses and automated sites, along with precipitation, antecedent streamflow and indices of the El Niño/Southern Oscillation are used in computerized statistical and simulation models to prepare runoff forecasts. Unless otherwise specified, all forecasts are for flows that would occur naturally without any upstream influences.

Of course “forecasts of any kind, of course, are not perfect,” Goats said.