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Jed Boal reporting Steady snowfall this winter is good news for Utah's water supply. Over the decades, though, a decrease in the snowpack raised questions for hydrologists.
Hydrologists measure snowpack at a Trial Lake site in the Uintas every winter. An automated station transmits hourly data, but scientists, like Randy Julander and Tim Bardsley, started to survey snow depth here 80 years ago, taking measurements by hand.
Snow depth this year is what it should be: about 74 inches, or 22 inches of water. "2007 was nothing but a complete and total disaster. It's good to see snowpack rebounding and above average in almost all cases," said Julander, hydrologist for the National Resources Conservation Service (NCRS) Snow Survey.
But over the decades, numbers at this location show a 10- to 12-percent decline in the amount of water in the snow. "A lot of researchers would look at that specific thing and say, 'We've seen a decline in snowpack, we've seen an increase in temperature, ergo it must be global warming,'" Julander said.
Or could there be other factors involved? A photo of the snow survey site taken in 1936 shows a pole in the center--a measurement location. In this same view today, vegetation crowds the site. "As vegetation grows, it alters the snow accumulation at specific points," Julander explained.
Hydrologists are taking thorough measurements so they can determine whether the encroachment of all of the trees has affected the snow data over the years. "That's what we're seeing at this particular course," Julander said.
Numbers from the National Climatic Data Center show Utah was two degrees warmer last decade than the 100-year average. Among 16 snow sites with longevity, each that shows a change in vegetation also shows a decline in snowpack. Each without a change in vegetation shows no decline in snowpack. "Global warming may have some impact here. The predominant influence of the decline here is vegetation encroachment," Julander said.
That's not to say climate change won't affect Utah snowpack, but today there's no link between Utah snowpack and global warming.
Snow data is being used to index global warming, but the hydrologists insist data must be consistent over the period of record to have any value.
