Utah’s winter snowpack has provided a real-world example of the shortcomings of only looking at average conditions, according to the Jan. 1 Water Supply Outlook Report.As of Jan. 1, the statewide (average of all sites) snow water equivalent (SWE) was close to normal — 95% of median — but while northern Utah watersheds were generally above normal, southern Utah — southwestern Utah in particular — has had a “terrible” start to its snowpack season, the report said in a summary. Almost no measurable snow fell in southwestern Utah during December, and the regional snow water equivalent was consequently in the bottom 10th percentile of all observations by the end of the month. Credit: Utah Snow SurveyFurthermore, five SNOTEL sites in that area were at record lows for Jan. 1 SWE; four had no snow at all. By contrast, snowpack conditions were at or above normal for all northern Utah watersheds. Last year, Utah’s statewide snowpack was only at 69% on Jan. 1, and the state ended up well-above normal by April when the snowpack peaked. There’s still ample time for this winter to get on track for all areas, the report said.December precipitation in Utah was below normal at 89%, which brings the water-year-to-date precipitation to 92% of normal. Similar to the snow water equivalent, as of Jan. 1, Utah’s northern watersheds had close to normal water-year-to-date precipitation while the southeastern Utah and Escalante-Paria regions were close to 75% of normal and southwestern Utah was faring the worst at 60% of normal, the report said.Credit: Utah Snow SurveyAll of Utah’s SNOTEL sites have soil moisture sensors at 2-inch, 8-inch, and 20-inch depths. Each sensor location also has an estimated saturation point, based on soil characteristics and past sensor behavior. Data are combined from these three sensors and then amalgamated from all of Utah’s sites to produce a singular, statewide value for soil moisture percent of saturation that can be compared with previous years.When looking at Jan. 1 conditions through that lens, statewide soil moisture is at 39% of saturation, which is down 8% from last year at this time, and at around the 20th percentile of all observations, according to the report. Credit: Utah Snow SurveyUtah’s reservoir storage is currently at 75% of capacity, down 3% from this time last year. Whereas the Upper Sevier watershed has seen the largest drop in reservoir storage since last year, the largest increase in storage during that time was just downstream for the Lower Sevier portion of the drainage where the Sevier Bridge Reservoir, also known as Yuba, was up almost 20,000 acre-feet from last year, the equivalent of a roughly 8% increase in storage (from 27% to 35% of capacity). Jan. 1 forecasts have significant uncertainty compared with those issued during spring months (closer to peak snowpack conditions) and are meant to be advisory only, the report advised, noting that NRCS streamflow forecasts for snowmelt runoff volume are included at the end of the report for reference purposes. Surface Water Supply Indices (SWSI) for Utah basins combine the state’s current reservoir levels with the additional volume of water anticipated for each watershed based on our streamflow forecasts. Because the Jan. 1 forecasts are meant to be advisory-only, the report does not include SWSI values for Utah basins, but those are forthcoming in the Feb. 1 Water Supply Outlook Report.Snow water equivalent and precipitation in the Great Salt Lake basin are 103% and 107% of normal, respectively, the report said. Soil moisture is at 36% of saturation (76% of normal), and the basin’s reservoir storage is at 79% of capacity. Great Salt Lake inflow forecast for April through July is “very rough” at this early stage and meant to be advisory-only. It ranges from 22 thousand acre-feet (kaf) to 1210 kaf, with the most probable value closer to 615 kaf. Credit: Utah Snow SurveySimilarly, the report’s predictions for lake level rise from April until peak lake stage ranges from 0.0 to 1.16 feet, with a 50th exceedance probability (most probable) rise of around 0.5 ft. This is a very wide range of possible outcomes, the report notes, adding that the ability to predict lake inflow and rise will improve as the snowpack season progresses.  Finally, the report reminds readers that its inclusion of GSL inflow forecasts and predicted lake level rise is meant to provide rough guidance for Utah’s water managers in light of the high level of interest in the lake’s condition and numerous actions to restore lake levels.See the full report below. WSOR_Jan_2025DownloadThe post Water Supply Outlook Report for January shows stark split between northern and southern Utah snowpack appeared first on Park Record.