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by Allen Best

In 2008, Science magazine published an essay called “Stationarity is Dead: Whither Water Management.” In the essay, PCD Milly, a research hydrologist with the U.S. Geological Survey, and others, argued that climate change was upsetting all the apple carts of water management. Water management, they said, was set up for a 20th century climatic regime that had changed and would change further.

Thirteen years late, the evidence continues to accumulate in support of that thesis. The latest is a report, “A low-to-no snow future and its impacts on water resources in the western United States.”

The authors, primarily from the Lawrence Berkeley National Laboratory  and other University of California schools,  overlap with the research team for the  SAIL project in Gothic. The report has six authors from California, one from Nevada and one from Colorado, Denver Water’s Laurna Kaatz.

The report published in Nature Reviews Earth & Environment provides a bold warning about the strong potential for snowless winters becoming relatively commonplace by mid-century and beyond, especially in the coastal ranges and Sierra Nevada of the West Coast.

It got significant attention from the Washington Post last week under a headline of: “Snow may vanish for years at a time in Mountain West with climate warming.”

That’s not exactly news. I may be low on the journalistic totem pole, but I’ve been writing about this for at least a decade. And no one single headline can do justice to the variations of Western topography.

In a 2016 story I wrote:

“Contrary to what some have said, those who professionally study the changing climate and its rising temperatures do not foresee an end to snow. Or winter. Or skiing.

At least not everywhere, nor in a set amount of time—the next 25 to 30 years—that matters to many North American mountain towns.

They do see, however, continued increases in both day and nighttime temperatures that might threaten the livelihood of some ski areas, especially those at lower elevations, which could have a ripple effect on the industry.”

This new report delivers relatively little new information but does prominently hoist a talking point around the concept of low- and no-snow years.

The report synthesized 18 models about future precipitation and temperatures. The modeling foresees relatively little dramatic change until about mid-century. Then, changes occur abruptly.

Only 8% to 14% of years were classified as low- to no-snow over the period of 1950 to 2000.

This compares to 78% to 94% between 2050 and 2099.

The report defines a phenomenon called episodic low- to no snow as being five consecutive years in which more than 50% of the basin area experiences low-to-no snow. This emerges in the late 2040s in California, but in the 2060s for most basins.

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Persistent low to no snow is defined as 10 consecutive years of greater than 5% of the basin area having low to no snow. That is predicted to occur in the late 2050s in California and as late as the end of the 2070s in the upper Colorado River Basin.

This is a broad-brush of a report. It distinguishes among the four major mountain ranges that have been studied, but provides relatively little differentiation other than to note a substantial distinction between the West Coast and the Rockies. And there is great uncertainty. “The large spread in projected changes at mid-century to end of century highlights the lack of consensus on this time to emerge of low- to no snow.”

To be clear, though, the science all points in the same direction. Just how different that future will be for babies born in 2021 when they became octogenarians is revealed in this sentence: “Although not impossible, it is unlikely that a complete disappearance of snow in the Western United States will occur before the end of the 21st century, even under a high-emissions scenario.”

The report bills itself as a “call to action” and warns of the “dire implications of a low- to no-snow future, given its central role in mountainous watershed behavior, ecosystem function, and ultimately, downstream water availability.”

Most of us understand this so well that it seems trite to even mention it, but the water infrastructure of the 20th century was built around the idea that fallen snow —the majority of precipitation in most Western basins, including those of Colorado —builds up over winter and then somewhat leisurely melts, often far into summer.

That absence of stationarity will have huge consequences of which we are only starting to reckon.

Allen Best
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