From The Colorado Sun (Amanda K. Clark):

Raising the 55-year-old dam near Boulder is essential to keep a stable water supply in a changing climate, utility says. Residents insist conservation could be just as effective.

Denver Water — Colorado’s largest and oldest utility company — in July 2017 received one of the final permits needed to raise Gross Reservoir Dam by 131 feet to increase water storage capacity by 77,000 acre-feet, or an additional 25 billion gallons of Western Slope water…

The expansion, in the works for more than a decade, is part of the company’s long-term plan to help meet increasing water demands along the Front Range and buffer customers from future water-supply variability due to climate change…

Denver Water has been met with sustained opposition from Boulder County residents and a handful of environmental groups who say the utility can address its water needs through expanded water conservation efforts on the Front Range.

But with Colorado’s population growth showing no signs of slowing, water conservation may be inadequate to address projected shortages in the coming decades.

Other concerns raised by opponents include sustained disruption to surrounding residents, increased traffic, health concerns and environmental impacts to fish and wildlife.

Gross Reservoir is filled primarily from snowmelt that flows from the Fraser River, a tributary of the Colorado River. The water is transported underground from west of the Continental Divide to the east by a pipeline called the Moffat Water Tunnel.

The controversy over the Gross Reservoir expansion, estimated to cost $464 million, echoes an all-too-familiar story: a highly contentious discussion of tradeoffs that has rippled across the Western United States for decades.

As cities and states across the West grapple with swelling population alongside diminishing water supplies as a result of climate change, water-resource agencies such as Denver Water are faced with the delicate task of balancing the health of ecosystems with municipal, agricultural and recreational needs…

Jeff Martin, Denver Water’s project manager for the expansion project, doesn’t skirt around the controversy. He recognizes that the project is going to cause disruption and says that Denver Water has worked with the residents to find ways to minimize the project’s impact.

“This has been a process,” Martin said. “We started in 2004, it took 13 years to move through the environmental assessment and permitting process. And we’ve made a lot of changes and adjustments to our plans since the beginning.”

“No single solution is out there,” he said. “Our problem is rooted in demand and resiliency, and what I mean by resilience is that we have to make sure we have the water when we need it, and where.”

[…]

For Patty Limerick, director of the CU Boulder’s Center for the American West and former Colorado Historian, you can’t talk about water issues on the Front Range without first looking back in time.

When early white explorers arrived here, they deemed the Front Range unfit for settlement due to lack of water. Today, 1.4 million Denver residents have access to clean drinking water due in large part to Denver Water’s enormous infrastructure web that diverts water from the South Platte, Blue, Williams Fork and Fraser river watersheds to be stored in a network of reservoirs spread over eight counties, including Dillon, Strontia Springs and Cheesman.

“One thing that I find fascinating, and is important to talk about, is the incredible amount of engineering that had to occur to make any of this possible in the first place,” Limerick said.

“We, as a society, have to recognize the improbable comfort that was made possible by a taken-for-granted, but truly astonishing, water infrastructure that was put in place a hundred years ago.”

[…]

“The year 2018 was very similar to what we would expect to see under a climate change regime. And that was a very intense but short-term drought,” said Taryn Finnessey, senior climate change specialist with the Colorado Water Conservation Board.

“We saw some reservoirs in the state declined by 50 percent in a three- to four-month period. So that obviously could not be sustained multiple years in a row,” she said. “Water providers are increasingly integrating climate change models into their water supply projections. They know that what we’ve seen in the past might not fully represent what we might see in the future. Denver Water is one of the more advanced utilities when it comes to this.”

Finnessey says it’s not just about how much precipitation falls from year to year. It also has a lot to do with increasing temperatures, contributing to the long-term drying out of the West, a phenomenon scientists are referring to as aridification. As temperatures rise, more moisture is sucked up by the atmosphere through evapotranspiration, leaving less viable water for humans-use in the system.

“We are planning for infrastructure that will be built in the next 20 years, that is supposed to last for the following 100 years,” said Reagan Waskom, director of Colorado State University’s Colorado Water Institute. “Our world is changing significantly faster than that. And not in a linear way. How do we adapt to that?

“Water managers have to plan for extremes,” he added. “A year like this year is an argument for reservoirs. Even with climate change, you’re still gonna have some good years. And we need to be able to capture it and save it for the bad years, whether that’s in underground aquifers or in reservoirs.”