San Juan Mountains 2020-21 WATER YEAR RECAP ~ The Land Desk

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SNOW/WATER EQUIVALENT

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Happy (belated) Water Wonk New Year! Okay, maybe water wonks don’t get all tipsy and start reciting Western water law at midnight on Oct. 1, but it does mark the beginning of the new water year. That means we can all dump out those precipitation gauges and reset the snowpack statistics and hopefully put the past year behind us. But before we do, let’s take a look back at Water Year 2021 and the good, the bad, and the oh so ugly. 

Pretty much everyone west of the Continental Divide—as well as some to the east—will be happy to bid the past water year adieu. Streamflows across the region shrunk; fish died off; reservoir levels declined, taking hydropower generation down with them; irrigators watched their ditches run dry long before harvest time; the bathtub ring around Lake Powell grew to 160 feet high; wildfires raged with unprecedented intensity in northern California, Oregon, and Montana; and a Tier 1 shortage was called on the Colorado River for the first time ever, meaning some users will see cuts next year.

What strikes me most is that seven months ago, as winter turned to spring, the snowpack levels—i.e. the giant reservoir that feeds those depleted streams—did not foretell the dryness to come. Sure, the snow water equivalent was below average at most San Juan Mountain SNOTEL sites, but not disastrously so. The skiing was decent as long as you didn’t get hit by an avalanche and the high country remained blanketed in white into the spring—at least in Colorado. 

Columbus Basin is in Southwest Colorado’s La Plata Mountains, which seemed to repel storms last winter, making it one of the driest areas of the state. Other sites further north in the San Juans recorded snow levels as high as 85 percent of average and the Rio Grande headwaters to the east even saw above average snow levels.¹ One might have expected the rivers fed by that snowpack to run at 85 percent of average, as well. For the most part, they did not. 

It was as if the snow, instead of melting and running off down mountainsides and into reservoirs, just evaporated or soaked into the ground. And that’s pretty much what happened. “It didn’t feel like a low winter to me,” Darrin Parmenter, La Plata County director for the Colorado State University Extension Office, told me this spring. “It just didn’t run off. You have to recharge soil moisture. It has to go through that sponge before it gets to the water table. The Animas didn’t come up until we had our only rain.” 

What didn’t soak into the ground, which was parched due to the lack of a 2020 monsoon and two decades of aridification, wafted into the air via evapotranspiration and snow sublimation, phenomena enhanced by dry air, incessant spring winds, warming temperatures, and dust on the snow, which reduces albedo. That left less snowmelt to feed the rivers and reservoirs and left many farmers high and dry early in the growing season. 

Animas River flows as it runs through Durango, Colorado, for water year 2021, 2020, and median for the period of record (1896-2021). 

As you can see from the above graph, the Animas River was unusually low through the spring and early summer. It wasn’t until the monsoon arrived in full force in late July that it showed some signs of recovery. But even that wasn’t enough to replenish reservoirs, especially since the monsoon was not distributed equally across the West

And even though the rains were plentiful in some areas, so too were the above average temperatures, thus offsetting some of the rain gains. 

The result? Widespread drought conditions across most of the Western U.S., with a few exceptions. Over the last year, drought has intensified dramatically in California and the Northwest, while subsiding slightly in Colorado and Arizona. Nevertheless, only a few patches of land remain that aren’t in some stage of drought. 

The good news is we are going into the new water year with some new water: A storm just blanketed the San Juan Mountains with white, pushing the snow water equivalent up to two inches at the Molas Pass SNOTEL site. The bad news is, we are in a deep, dry hole left by 22 years of aridification. It will take a lot of big storms, all winter long, to get us out of it.

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