Despite a forecast for conditions that could have resulted in large loss of snowpack yesterday, atmospheric conditions lined up just right to not only avoid the loss but actually gain a very large amount of snow-water-equivalent (SWE). Read on for the details, as well as for an example from the spring of 2010 that illustrates a very large rain-on-snow event.
It’s no secret that 2018 has been much warmer than we’re used to (in January, 5°F warmer than normal across the whole watershed and as high as 7°F above average in Island Park). At the same time, HFF has been reporting SWE (snow-water equivalent) numbers at 96% of average at the end of January (as high as 103% of average this past week), above average streamflow, and near average precipitation across the watershed (not to mention 111% of average Jan. precipitation at Island Park). If you’re looking out your window in Island Park right now, you’re probably wondering, “How is that possible?”
Over the month of January, water-year precipitation increased from 87% of average to 93% of average, and snow-water-equivalent increased from 89% of average to 96% of average.
Streamflow throughout the watershed was generally above average, including outflow from Island Park Reservoir, which, at 508 cfs, was 134% of average and the highest since the winter of 2011-2012.
The only negative aspect of the current water situation is that January was much warmer than average, limiting snow accumulation at lower elevations and setting up the snowpack to melt early and rapidly.
As the climate warms and water availability becomes more uncertain, the future of wild trout fisheries in the Henry’s Fork depends critically on science-based management that ensures favorable streamflow, good water quality, and a positive fishing experience.
At the end of each year, HFF takes a moment to reflect on all that was accomplished and all the great things we were a part of. To keep the tradition going, HFF is taking a look back at the "Top-10" programmatic accomplishments of 2017. You can also take a look back at HFF's Top 10 for 2014,2015, and 2016.
December precipitation was only 51% of average across the Henry's Fork watershed. However, water year-to-date precipitation and snow-water-equivalent are at 87% and 89% of average, respectively. And, thanks to above-average precipitation during water year 2017, the upper Snake River reservoir system is 87% full, and winter streamflow is above average. Long-range forecasts call for average to above-average precipitation for the remainder of the winter, so the overall water-supply outlook remains good as we head into the New Year.