Eagle River Coalition: Breaking down snowpack in the Eagle River Valley

With the recent snowfall and cold temperatures we’ve been experiencing, it is officially winter here in the Eagle Valley. Not only is this snow advantageous for our ski resorts and communities in the winter, but it also is what sustains local river recreation in the summer.
Roughly 80% of summer’s flows result from the accumulated snowpack over the winter months, so when we hear that we are over 100% of the average snowpack, it is reasonable to assume that we are looking ahead to a summer with at least normal flows. But is this really the case? Let’s dive in and find out.
When a percentage of average snowpack is referenced, that number is based on the snow water equivalent. Snow water equivalent is how much water is present when the snow is melted down. The primary reason this value is measured based on liquid water, rather than snow, is because the measurements for water are consistent, while the density of snow can vary widely.
Snow can be light and fluffy, or heavy and dense, and is affected due to multiple factors. Weather conditions, such as temperature, influence the snow that falls. For example, with air temperatures between 15-19 degrees Fahrenheit, 20 inches of snow would equate to 1 inch of snow water equivalent. It’s really light and fluffy, the stuff we like to ski on.
For a storm with warmer air temperatures of between 28-34 degrees Fahrenheit it would only take 10 inches of snow to make 1 inch of snow water equivalent. For example, Eagle County received a large storm in November with fairly warm air temperatures between 28-34 degrees. This resulted in a heavy and high snow water equivalent to start the season, putting us above average early in the water year.

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Another term frequently referenced during discussions of snowpack is the concept of “30-year average.” The Natural Resources Conservation Service is tasked with tracking snow water equivalent, and the group has tracked three 30-year periods over 50 years: 1971-2000, 1981-2010 and 1991-2020.
The Natural Resources Conservation Service uses 30-year averages because each year’s weather, snowpack and streamflows are highly variable. In some years, we see big storms early in the season and drier springs, and in other years we see consistent heavy storms or very dry periods and the snow water equivalent can differ greatly.
An important thing to note is that the Natural Resources Conservation Service uses the median measurement to describe the average referenced in 30-year averages. This is because the median is found in the middle of a set of data, and is less skewed by outliers. Outliers can have outsized influences on our understanding of the average, but using the median reduces their influence.
According to Bill Hoblitzel, a hydrologist with Lotic Hydrological, as a general trend in Colorado, the most recent 30-year period has been drier and warmer than previous 30-year periods on record.
We can observe this trend by analyzing data from the local Snow Telemetry Network (SNOTEL) sites at Vail Mountain, Beaver Creek and McCoy Park. We compared the snow water equivalent data from December 2024 with averages from two different 30-year periods. December 2024’s snowpack was approximately 123% of the 1991–2020 average. However, when compared with the 1971–2000 average, it was only 113% of the average — a difference of 10%.
The Eagle River Basin’s snowpack has been at or slightly above the 30-year average for most of the 2025 water year, which began in October 2024. Throughout other basins in the region this is similar as well, with the Blue River Basin snowpack mostly above average for the past two months and the White River Valley lingering below average.
Keep this information in mind as you continue to hear updates about snow water equivalent and 30-year averages, and let’s keep hoping for more precipitation. Not only will this precipitation benefit our number of powder days, but it will also keep our river healthy and flowing well into 2025.
Rose Sandell is the education and outreach coordinator for Eagle River Coalition, which has a mission to advocate for the health and conservation of the Upper Colorado and Eagle River basins through research, education, and projects.