NRCS releases first water supply report of the year
On Jan. 1, the U.S. Department of Agriculture’s Natural Resources Conservation Service (NRCS) published the January 2025 Wyoming Basin and Water Supply Outlook Report, which analyzes snowpack, precipitation, streamflow and reservoir storage across the state of Wyoming.
The report also assesses the water supply outlook for the entire state of Wyoming, as well as individual basins including the Snake River, Madison Headwaters, Yellowstone River, Wind River, Big Horn River, Shoshone River, Powder River, Tongue River, Belle Fourche River, Cheyenne River, Upper North Platte River, Lower North Platte River, Laramie River, Sweetwater River, South Platte River, Little Snake River, Upper Green River, Lower Green River and Upper Bear River basins.
Forecast uncertainty
NRCS notes because most of the annual streamflow in the western U.S. originates as snowfall, which accumulates in the mountains during winter and early spring, hydrologists are able to estimate the runoff which will occur when snowpack melts.
“Measurements of snow water equivalent (SWE) at selected manual snow courses and automated snowpack telemetry (SNOTEL) 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,” reads the report. “Unless otherwise specified, all forecasts are for flows which would occur naturally without any upstream influences.”
However, these predictions are by no means perfect and are subject to change due to the uncertainty of future weather conditions, forecasting procedures and errors in the data. So, the agency encourages individuals to interpret their forecast as a range of values with specific probabilities of occurrence instead of as a single value.
NRCS further notes, the wider the spread among these values, the more uncertain the forecast will be. As the season progresses, forecasts will likely become more accurate because a greater portion of future weather conditions will be known.
Snowpack and precipitation
As of Jan. 1, SWE across the state was 76 percent of median. The highest SWE was reported in the Lower Green River Basin at 101 percent of median, and the lowest SWE was reported in the South Platte River Basin at 11 percent of median.
According to NRCS, the Cheyenne, South Platte, Belle Fourche, Powder, Shoshone, Tongue, Big Horn, Yellowstone, Wind, Laramie, Madison Headwaters, Sweetwater, Snake, Lower North Platte and Upper North Platte river basins were below the minimum SWE recorded from 1991 to 2020.
Additionally, the report notes the Upper Green River Basin had the highest precipitation for the month at 127 percent of median, while the South Platte River Basin had the lowest amount of precipitation for the month at 20 percent of median.
Streamflow yields
NRCS forecasts streamflow yields from April through September across all Wyoming basins – except the Cheyenne, Little Snake and Green river basins – to average 77 percent.
Streamflow yields for these three exceptions are expected to respectively average 79, 85 and 87 percent of median from April through July.
Expected streamflow yields for individual basins across Wyoming include the Big Horn Basin at 56 percent of median, the Tongue River Basin at 63 percent of median, both the Wind River and Powder River basins at 67 percent of median, the Shoshone River Basin at 75 percent of median, the Sweetwater River Basin at 76 percent of median and both the Yellowstone and Cheyenne River basins at 79 percent of median.
Other streamflow yields expected across the state include the Snake River Basin at 81 percent of median, both the Upper and Lower North Platte river basins at 82 percent of median and the Laramie River Basin at 91 percent of median.
Reservoir storage
For the entire state of Wyoming, NRCS reports average reservoir storage at 89 percent of median, with the majority of reservoirs in the state reporting below median.
According to NRCS, reservoirs in the Laramie River, Wind River, Upper Bear River, Belle Fourche River and Cheyenne River basins reported numbers below median at 50 percent, 82 percent, 87 percent, 89 percent and 89 percent, respectively.
Likewise, the Buffalo Bill Reservoir on the Shoshone River was 83 percent of median.
Reservoirs in the Lower North Platte River Basin and Upper Green River Basin both reported near median at 92 percent, while reservoirs in the Upper North Platte River Basin were 95 percent of median and the Boyson Reservoir in the Big Horn Basin was at 96 percent of median.
Additionally, reservoirs in the Lower Green River Basin were at 100 percent of median and those in the Snake River Basin were at 105 percent of median.
Hannah Bugas is the managing editor of the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.
