Some of those on the campaign trail call for more storage. They need to visit Green Mountain Reservoir.
by Allen Best
No place in Colorado that I have visited offers such blunt testimony to the warming, drying climate than Green Mountain Reservoir. It also poses a question to those politicians whose answer to non-winters and ever-hotter summers is more dams and reservoirs.
The reservoir between Silverthorne and Kremmling was 14% full during Labor Day weekend, according to the U.S. Bureau of Reclamation, the operator. Put another way, it was 86% empty.
That’s worse even than the roughly 78% empty at Lake Powell, the reservoir located roughly 700 river miles downstream from Green Mountain.
Green Mountain was part of Colorado’s mission begun in the 19th century to put water to “beneficial use,” a central axiom of state water law. Pioneer settlers did an admirable job of this, in the beginning using nothing more than horses, oxen and human labor.
In 1902, the federal government became a partner, creating the Bureau of Reclamation. Over the next roughly 90 years, the federal treasury was visited repeatedly to prevent “waste” of any portion of the Colorado River flowing into the Pacific Ocean.
Construction of Green Mountain Dam was part of that work. During the hot, dry 1930s, farmers in the Fort Collins-Longmont-Greeley area wanted to import water from the Colorado River headwaters near Grand Lake. Western Slope irrigators objected. Farms in the Grand Junction area would lose late-season water needed to get their crops and orchards across the finish line.
Green Mountain was the compromise. And it has worked out well. A pool of 66,000 acre-feet of water was reserved for down-stream irrigators in the Grand Junction area. Deliveries in this canal usually continue through October, sometimes later.
This year was different. For the first time in 110-plus years, deliveries ended in late August.
In April, the Glenwood Springs-based Colorado River Water Conservation District issued a warning. Green Mountain was the lowest it had been since filling during World War II. This jeopardized the late-summer flows to irrigators who took delivery of water from the Government Highline Canal. The canal diverts water from the Colorado River at the Roller Dam, a short distance upstream from Palisade. It then distributes water to farms and orchards for 55 miles, nearly to the Utah border.
This year, in a testament to cooperation, the Colorado River District and Colorado Water Conservation Board ponied up more than $1 million to buy use of water. Water was tapped from headwaters reservoirs, most notably Wolford and Williams Fork, near Kremmling, and Ruedi, near Basalt. Others, including Front Range diverters, helped.
Irrigators got only 50% of their normal water. In response, many switched crops to varieties of plants that could survive with less water.
Even so, by late August, the water was running out. The Grand Valley Water Users Association, operator of the canal, stopped deliveries on September 3. Maybe monsoon rains will deliver water to resume operations, but that’s the story for now.
Once again, the idea that we just need to store more is entirely too simplistic. Yes, saving for a rainy day is always good, but this idea that we can build our way to more water defies ample evidence about the warming, drying climate.
We can have droughts, yes. They come and go. But the science clearly shows that these hot, dry years of the 21st century will not be ephemeral. They have been driven by a warming climate caused by accumulating greenhouse gas emissions.
In the 20th century, the Colorado River delivered about 15.2 million acre-feet. In this century, the annual flows have declined to 12.2 million acre-feet. Since 2020, average flows have declined even more, to 10 million acre-feet. And this recent span included a very, very big snow year, in 2022-23, a three-wire winter like those of old. But the spring was like those of the 21st century, early and uncommonly warm.
The pitiful storage in Green Mountain, whose shoreline is seen in the above photograph I took on Aug. 17, testifies to this warming, drying climate. So does the canal near Grand Junction where deliveries were cut off last week for the first time in 110 years. And then we have near doubling of 95 degree-plus days in Denver during last 30 years as compared to the three decades before as reported by KUSA.
Might we figure out better infrastructure? Maybe. The idea of storing water underground, as Greeley began doing several years ago, intrigues. It requires more energy but greatly reduces evaporative loss.
The federal government in its documents has excised climate change. So have many politicians in Colorado speaking on the stump, hewing to the recent version of political correctness.
If there are ideas for storing water that don’t assume a return to the climate of the 20th century, I’m all for hearing them. But to think this is just another drought defies tons of evidence.
See also:
“Does 80% of Colorado’s precipitation really fall west of the Continental Divide?” Russ Schumacher, Jan. 17, 2024.
“A first in the 110-year history of this canal,” Big Pivots, Sept. 3, 2026
“Amid the y’alls, two themes at the Colorado Water Congress conference,” Big Pivots, Aug. 31, 2026
“Rare optimism about the Colorado River,” Big Pivots, Aug. 24, 2026
- Implications of Michigan case for Craig coal unit - September 26, 2026
- A big widening of this narrow electronic highway - September 25, 2026
- Two Denver-based firms get geothermal grants - September 21, 2026
Artificial recharge of groundwater, variously called “aquifer storage and recovery” (ASR) or “managed aquifer recharge” (MAR) should be part of a well-considered plan to enhance water storage and later availability for use. ET losses are low (as you point out) as compared to surface storage, but there are other factors to be considered:
• Can you, in a legal sense, maintain dominion and control of the recharged water? Or, are adjacent wells that are not part of your plan going to divert some of the water? Will you encounter difficult and expensive legal challenges that quickly turn into time and funding issues? Your project may be forced to give up a substantial percentage of its recharged water simply as a bargaining chip to get objectors off your back and out of your court case.
• Are there timing issues with recovering the water your project has recharged? Or is some of the water simply slipping away from you due to the fact that all water, including groundwater, is always moving? Astute engineering, accurate onsite data analysis, and good computer modeling can overcome some of these questions, but perhaps not all. There are always unknowns with respect to groundwater and aquifers, and this typically translates into less than 100% recovery of recharged water.
• Do you expect water quality issues? i.e., is the recharged water chemistry compatible with the in-situ groundwater, or is pre-treatment necessary to minimize siltation, aquifer pore clogging, or chemical precipitation?
Thank you, Alan for providing this great example of the record breaking dryness of 2026. As usual, Green Mountain reservoir is a complicated topic To round out the story, I think it would be useful to explore in a follow up article;
1) Was there water available in recent in wet years that could have been stored in a new reservoirs and carried over into 2026?
2) How much water did Denver provided to Reclamation in Williams Fork and Wolford reservoirs to payback for the water that was stored in Dillon, but owed to Green Mountain?
3). How much extra water was Green Mountain able to store because Denver paid Xcel Energy to reduce the Shoshone power plant call on the river during the spring runoff?
4) How much water could have been stored in Green Mountain if the Shoshone call had not been placed and would that have been enough to continue normal irrigation in the Grand Valley?
5). Is the Colorado River District potentially harming its constituents with its plan to own and operate the Shoshone call in the same manner as this year? ( Calling water downstream and running it out of the state during the spring runoff rather than storing water for West Slope irrigators to use after the runoff. I expect the Lower Basin states would love to see a continued full use of the Shoshone call ).
Yes there is a way to add water storage while increasing the farmers profits and benefits everyone that takes the long view.
It is called soil organic matter SOM.
If the entire southwest agricultural community would focus on soil health, we could see a huge difference.
Every 1 % increase in SOM is 26,000 gallons per acre of water holding capacity. Do the math.
Fallow is not the answer. When fully implemented, the 6 principles of soil health can easily increase SOM by 1/4% per year.