A Dam Waste In the Age of Megadrought

Mining explosions and summertime thunder can sound remarkably similar. In my rural Colorado neighborhood, 10 miles southwest of Boulder, the smaller blasts that clear ground for the expansion of Gross Dam can be mistaken for the pleasant rumbling of sky gods. But the shock waves of the bigger detonations, the ones that have been tearing apart massive chunks of mountainside, about a mile away as the crow flies, are unmistakable. The concussive booms, occurring randomly several times a weeksince May 2022, compress my chest, stop me in my tracks and terrify my dog. 

Private utility Denver Water is raising Gross Dam by 131 feet with the hope of holding back nearly three times the water it does today. The project will take about six years to raise the concrete edifice to 471 feet — about as tall as the 41-story Spire high-rise in downtown Denver — making Gross the tallest dam in Colorado. Originally completed in 1954, the structure was engineered with expansion in mind, and the new plan, costing nearly $500 million, is to increase the flexibility of Denver Water’s supply should wildfires, drought, operational problems or emergencies affect other parts of the system. Neighbors fought the expansion, but a small hydroelectric turbine tacked onto the original dam shifted jurisdiction to the federal government, effectively allowing the company to avoid local environmental review. The company pried agreement from Boulder County by dropping its own lawsuit against the county and paying into a $12.5 million compensation fund for the county and local residents. (Disclosure: My wife, as owner of the house where I live, received a portion as compensation for the noise, dust and traffic of construction.)

Gross Dam blocks South Boulder Creek to form Gross Reservoir, but this source alone was too modest to sustain the grand city that Denver’s administrators envisaged back in the early 20^th century. By 1921, city planners had secured rights to the Colorado River, allowing Gross Reservoir to be filled also with water from the Fraser River, a major tributary of the Colorado that flows on the other side of the Continental Divide. Today the Fraser is partly diverted 6.2 miles via a tunnel under the Rocky Mountains, relocating to the east water that nature intended to run west to the Pacific Ocean. The broad purpose of this trans-basin diversion is to slake the thirst of the approximately 1.5 million people — about 25% of the state’s population — who rely on Denver Water. The utility’s collection system captures enough rain and snowmelt to serve about 600,000 households in an average year.

Denver’s population is among the 40 million people from Wyoming to California who depend on the Colorado River for at least part of their water supply. But while the West’s population continues to grow, climate models show increasing temperatures in the upper Colorado River basin (Colorado, Wyoming and parts of Arizona, Utah and New Mexico), meaning more evaporation, and more precipitation falling not as snow but as rain, which soaks into the ground before it can be captured. The ongoing fight over trans-basin diversions along Colorado’s Front Range are a microcosm of the new global climate realities.

To its credit, the city of Denver has enacted water conservation measures, improved storm-water runoff designs and put in place other offsets of water use. Nonetheless, it collects around half its water from Colorado River tributaries. The utility claims it will only draw extra water from the western slope for Gross Reservoir in “high flow” years when the snowpack is at average depths or more. “Once the additional space in Gross Reservoir is filled, diversion patterns will look much the same way they would without the expansion,” says Denver Water’s Todd Hartman.

But in a warmer West, those high-flow years may never come — which is to say, Gross Reservoir’s new capacity may never be filled. The new dam could be a study in overnight obsolescence.

“Denver Water is building a giant monument to climate change denial,” says Teagen Blakey, president of The Environmental Group, a local advocacy organization that’s one of six environmental groups suing to stop construction. “We will all be looking at a big hole in the ground, because the water isn’t there.”

The old saw attributed to Mark Twain, “Whiskey is for drinking and water is for fighting,” still rings true in the West. Water policy must serve diverse constituencies — cities, farms, the environment — that compete for a limited resource. Water rights in the region have historically been a zero-sum game: you either have rights to an adequate supply of the limited resource, or you don’t.

“The Colorado River simply does not have enough water to serve every city, farmer, rancher and industrialist in the West,” says Chris Canaly, director of the San Luis Valley Ecosystem Council, a public lands advocacy group in southern Colorado. At least 14 Native American tribes have water rights along the river, too. The Colorado River Compact, which has governed allocations across the states since 1922, was based on annual precipitation figures from the decade prior, which only the region’s Native populations — who were basically cut out of negotiations — could have told anyone were higher than historic averages. Thus was distribution of the river water based on a climate that didn’t even exist when it was being divided up.

Now, it’s much worse. The 20-year drought seizing the Southwest has brought water levels at Lake Powell and Lake Mead to almost below the levels of the hydroelectric turbines that are half of their raison d’être. This, along with the river’s inability to meet all the other demands placed on it, has forced a protracted renegotiation that pits the states against each other and state water laws in conflict with federal laws. The states missed a federal deadline this past January to conjure an agreement to somehow finagle their shared water use so that it accords with the Colorado’s declining capacity. Their failure has left the decision in the hands of the federal Bureau of Reclamation, which must come up with a plan by 2026, when the current rules expire. It’s not clear that the renegotiated Compact will fully account for Denver Water’s claims.

“If you’re trying to make logical sense of what the federal government does on the Colorado River, there isn’t any,” says Gary Wockner of Save the Colorado, another of the six co-litigants fighting Denver Water in federal court.

Denver Water touts the dam expansion as great for the economy, great for the environment and great for fire mitigation. The expanded dam will certainly be great for Denver, but at what cost?

Today, 80% of Colorado’s population lives east of the Continental Divide while 80% of its water flows to the west. Environmental groups argue that trans-basin diversions like the Fraser-to-Moffat Tunnel infrastructure decimate mountain rivers and impact local economies, ultimately reducing the Colorado River’s ability to sustain the West itself.

Such projects — and the fights to stop them — are a fact of life on the Front Range. The Adams Tunnel, managed by the Northern Colorado Water Conservation District, pumps water from the Grand Lake system on the western side, another feeder to the Colorado River. The Two Forks dam southwest of Denver (which would have incorporated water from another existing trans-basin diversion), was killed in 1990 by Republican Environmental Protection Agency administrator William Reilly. Denver Water likes to point out that opponents of that proposal favored raising Gross Dam instead, but that was 30 years ago, before today’s decades-long drought — which some researchers believe is just the beginning of a century-long drought like ones that tree-rings show have struck the southwest in the past.

Yet planners continue to seek these projects, and not just along the Colorado River. A current fight over the water in the Rio Grande, which originates in Colorado’s southwestern corner before forming part of the U.S.-Mexico border, shows that Denver Water’s Gross Dam play is not the only instance of cities seeking to grab water from rural areas to enable growth of questionable sustainability.

Near the headwaters of the Rio Grande, in the San Luis Valley, the unique geology has created two enormous aquifers that sustain the farmers and ranchers who have formed the basis of the valley’s economy since the 1800s (and will continue to sustain it in the 21^st century, according to the 2023 Colorado Water Plan). This is the number-two potato-growing region in the U.S., the first place in North America to cultivate quinoa, and the main supplier of barley to Coors beer. But a company called Renewable Water Resources, backed by real estate developers, absentee San Luis Valley ranchers and former Colorado Gov. Bill Owens, has proposed a trans-basin diversion from the valley across the mountains east to Douglas County, a morass of sprawling developments between Denver and Colorado Springs. It’s a prime example of not-smart growth — very little industry, many single-family homes, scant public transportation — and it’s growing fast. “Developers leave after their sales are complete, so government infrastructure is inadequate,” says Canaly. “Douglas County grew so fast that groundwork was incomplete.”

The Colorado Water Plan, adopted in 2023 as a framework for statewide collaboration around water planning, states that agriculture in the San Luis Valley is critical to the region’s economic stability. Yet RWR wants to offer farmers in the San Luis Valley a one-time payout of $50 million for their water rights. The company claims that by drawing only from the deeper of the two aquifers, the top aquifer — which farmers pull from — will not be affected. But that’s not how underground hydrology works, explains Matt Hildner, secretary of the San Luis Valley Water Conservation District, a quasi-utility that offsets water-well use in the valley with surface releases from small reservoirs. “You pull from one,” Hildner told me, “the other is going to be affected.”

The money would be locally controlled and doled out to help kickstart other revenue sources, but the loss of water would effectively kill many of the region’s farms and alter the culture and economy there forever, according to Hildner. Rapid groundwater depletion would also diminish the valley’s lakes and marshes, important stopovers for sandhill cranes and many other migrating birds.

An essentially identical proposal by American Water Development Inc. was defeated 35 years ago, and Douglas County commissioners rejected Renewable Water Resource’s proposal in May 2022, but the company continues to actively lobby in local elections and buy up water rights with the goal of transferring them out of the valley. The conflict has exposed racial inequities in this predominantly Latino community (originally Ute land), where the poverty rate is double the national figure. Locals who support environmental and cultural integrity face opposition from others hungry for a share of the $50 million RWR has dangled. Statewide opposition has also created strange bedfellows of Democratic Gov. Jared Polis and Trump bootlicker, Rep. Lauren Boebert. (Renewable Water Resources did not respond to requests for comment.)

“Our tactic is to bog down the RWR’s of the world by having them account for a united front of six counties” spread out across the greater San Luis Valley area, says Canaly. “One county cannot approve a trans-basin diversion when it impacts the other five.”

“People here want to preserve agricultural heritage,” says Hildner. “Losing that would leave a mark. We deserve to have an economy, too. Nobody wins if local economies collapse when one county secures water rights over the other.” He points out that both state and federal laws stipulate that any proposed water use must “prevent injury” to other parties. But trans-basin deliveries inevitably do injure someone.  

Local, regional and national interests will always be at play when negotiating water use in the West. The renegotiated Colorado Water Compact will likely set policy for the next 100 years, which are on track to be highly unpredictable climate-wise. “We need to learn to negotiate with each other, so everyone gets something,” says TEG’s Blakey.

According to Western Resource Advocates, a heavy-hitting environmental and policy group based in Boulder, use of the Colorado River must be cut by 25% to reverse the current volume of outstripping. The amount conserved every year would supply Los Angeles twice over.

The environmental coalition suing Denver Water has asked a judge in the U.S. District Court of Colorado to invalidate the federal permits arguing that the U.S. Army Corps of Engineers and the U.S. Fish and Wildlife Service failed to properly consider the environmental impacts from the enormous construction project. First brought in 2018, the suit was shot down in 2021, but an appeal has been granted.

Meanwhile, in the forested suburbs near Boulder, the explosions continue behind my house, and the beeping of trucks in reverse continues to haunt my dreams.