Climate change and Boulder’s dwindling water supply

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I am not a professional water supply engineer.

But I have learned enough in my decades of involvement in our city government to be very concerned about our future ability to continue to provide adequate water to existing residents and businesses, let alone the significant amounts of further development approved.

Steve PomeranceFor the camera

Boulder water comes from three sources:

The watershed belonging to the city lies on the eastern side of the watershed from South Arapahoe Peak to Niwot Ridge. It feeds many small reservoirs, then passes through a pipeline over the Peak-to-Peak highway to the Betasso processing plant on Sugarloaf Road.

We also have water down Middle Boulder Creek, stored in the Barker Reservoir near Nederland, and delivered via the Boulder Canyon gravity pipeline through the Boulder Canyon Hydroelectric Generating Station to Betasso.

About a third comes from us at the Colorado-Big Thompson Project (operated by the Northern Colorado Water Conservancy District), routed from the Colorado River across the Continental Divide, to Lake Carter near Loveland, and then to Boulder Reservoir, where it is processed.

According to city staff, we use more Colorado River water in dry years than in wet years.

A few data points I’ve seen regarding climate change: We’re in a 1,200-year drought. More than half of the contiguous United States was in drought by early May, government climate officials said. Colorado’s snowpack this year is well below average; some reports have it at two-thirds historical standards. Reservoirs above the Colorado River are being drained to keep enough water in Lake Powell and Lake Mead to run hydroelectric generators. NOAA’s final forecast for the season predicts the amount of water to reach Lake Powell this year at about 60 percent of average.

Our warmer, drier climate affects not only the amount of water, but also the timing of its arrival at Boulder Reservoirs.

Early runoff means that water is not stored in the snowpack for as long, so our reservoirs have to take in water sooner and therefore hold it longer, creating capacity issues as well as problems. exchanges that we make with other holders of water rights.

And of course, with less water overall, our ability to manage it becomes even more difficult.

A potentially bigger concern is our Colorado River water. The legal structure for ownership of this water is based on the Colorado River Compact of 1922. This agreement, formulated during a period of above-average flows, gives the lower basin states (California, Arizona and Nevada) the first rights to 7.5 million acre-feet per year (maf/year) on a 10-year moving average.

The upper basin states (Colorado, Wyoming, Utah and New Mexico) get all that is left except for a share due to Mexico (initially 1.5 maf/yr, but now reduced to something less , as I understand it.) An acre-foot of water covers an acre with water one foot deep.

That might sound like bad business for the upper pelvis, and it is. But as Patricia Rettig noted in her excellent May 5 camera commentary, some say “renegotiation is politically impossible.” Data on state usage in the upper basin is hard to come by, but an article I read has that total just under 5 maf/yr in 2020.

The problem is that the guaranteed 7.5 maf/yr for the Lower Basin plus Mexico’s share plus the current consumption of the Upper Basin is more water than the Colorado River.

This means that the upper pelvis should reduce its use, plain and simple. Under a 1948 agreement, Colorado gets 51.75% of the Upper Basin share.

Things are getting worse for Boulder because of “pre-compact rights.” These are pre-existing water rights to the Colorado River Compact. Another article I read indicated that users in the upper basin states held at least 2.2 maf/year of these rights; Colorado users own about half.

Additionally, there are conditional rights that predate the compact, but were not used when the compact was created. And then there are claims by indigenous peoples for additional rights, further reducing the yield available.

Thus, more than half of what, in theory, is left to water users in the upper basin states could go to these pre-compact water rights.

So there won’t be much left for our North District water shares (which serves multiple municipal and agricultural users, and has already fallen to around 70% of original yield), as the district was created in 1937, well after the compact . Thus, he is “junior” to all of these other entities.

So when it all hits the proverbial fan, the only question is – what, if anything, is left and who gets cut?

Steve Pomerance is a former member of the Boulder City Council. Email: [email protected]

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