On a rainy day in early May, Scott Wenning drove up an unmarked dirt road at the base of Mt. Sopris.
Heading up the mountain’s northwestern flank to the bottom of what skiers know as the “Crystal Chute,” he pointed upwards, at a narrow ribbon of snow — all that remained of last winter’s snowpack.
“That’s essentially our drinking water, historically,” he said.
Wenning manages Carbondale’s municipal water supply as the town’s assistant public works director, and he thinks a lot about how to mitigate risks to its water system.
Less snow is falling on Mt. Sopris than in the past, and Carbondale doesn’t have any reservoir storage. It relies almost exclusively on real-time water availability.
“That reliance creates risk,” said Wenning.
Every winter, the snow that accumulates on the mountain and then melts in the spring percolates underground into Nettle Creek, where the town of Carbondale has a water treatment plant at the base of Mt. Sopris. From there, the water travels through a 7-mile pipeline into town.
Nettle Creek is one of the three main sources of Carbondale’s municipal water supply, but as winters become warmer and drier, it doesn’t provide as much water as it used to.
According to Wenning, Nettle Creek used to flow at around 450 gallons per minute — even in the driest summer months. Now, he said, it’s down to 320 or 330 gallons per minute.
Wenning parked in an Aspen grove on Mt. Sopris’s lower flanks near where Nettle Creek bubbles to the surface in a spring, before it funnels into a pipe leading to the treatment plant.
But Wenning is less concerned about Nettle Creek’s decline than he is about another climate-related risk: wildfire. The Nettle Creek treatment plant sits in the middle of a forest — an area that could easily burn.
A wildfire could contaminate Nettle Creek with ash and organic debris that would clog the intake to the treatment plant, he said.
“That would decimate what we are providing for treated water for the town,” Wenning said.
Nettle Creek is a tributary of Crystal River, another one of Carbondale’s water sources that has also suffered from diminished flows in recent years. Those declines have pushed Wenning and other water managers to think more seriously in recent years about how climate change threatens Carbondale’s municipal water supply — a reality underscored by last winter’s record-low snowpack.
“We don't have enough resiliency to backstop those risks,” Wenning said, adding that water managers had started working on long-range planning to mitigate those risks.
“We were hoping to get through some of our projects that we had teed up for our capital expenditures before this kind of a winter hit, but it came first.”
After the record-setting March heatwave earlier this year, cooler temperatures and storms in April and May offered some life support to the high-elevation snowpack, delaying peak runoff on the Crystal River until early June.
The river’s historical average for peak runoff is 1,800 cfs, but this year’s peak was roughly half of that. By mid-June, it had dropped to roughly 450 cfs.
By August, Wenning predicted, “there will be no water or limited water in the Crystal River.”
This isn’t the first time a low-snow winter has stressed Carbondale’s water supply. In 2018, a dry winter followed by a dry summer caused water levels in the Crystal River to plummet.
The river was so low that senior water rights holders couldn’t divert the water they were legally allowed to use. They placed a “call” on the river, forcing junior water rights holders to reduce their water use on the Crystal, including the town of Carbondale.
Since Nettle Creek is a tributary of the Crystal River, the call nearly shut down the Nettle Creek treatment plant, threatening the municipal water supply to roughly 40 homes on the southern outskirts of Carbondale that rely exclusively on the Nettle Creek pipeline.
“To the best of anyone’s knowledge, there had never been a call on the Crystal River until 2018,” said Kevin Schorzman, the public works director for the town of Carbondale. “I think it was kind of like, ‘Oh, well, we live in this place where it's never going to happen,’ and then it happened.”
According to Schorzman, the situation prompted water managers to take action.
Their main challenge, Schorzman said, was: “How do we keep it from happening in the future?”
Climate adaptations
A few miles north of Mt. Sopris, down another dirt road that leads to the Roaring Fork River, Wenning stopped his car at a small brick building near the riverbank: The Roaring Fork Well House. Nearby are three wells that draw from the Roaring Fork River, providing another source of municipal water.
After the call on the Crystal in 2018, Carbondale water managers decided to reduce the town’s reliance on Nettle Creek by leaning more heavily on the Roaring Fork River, where the town also has water rights.
Carbondale currently has installed three wells — each of which produces roughly the same amount of water as the Nettle Creek plant (around 300 gallons per minute). But, the town has permits for seven more wells.
Shifting Carbondale’s focus to the Roaring Fork River makes sense, said Wenning. Since the Roaring Fork is a bigger river, it’s less affected by a low-snow year. The wells are also 40 feet deep, allowing them to access groundwater.
“I think even if water flows here drop off, we can still provide water to the town,” Wenning said.
The Roaring Fork Treatment Plant lies at the edge of the Carbondale Nature Park. Inside the barn-like building, a loud whirring sound echoes through the cavernous interior. The town recently installed new cartridge filter technology at the plant, expanding its capacity to treat water from 0.5 million gallons to 1.4 million gallons per day.
According to Wenning, the town plans to expand the plant’s capacity further to treat up to 2.3 million gallons per day from the Roaring Fork River alone — more than enough to meet Carbondale’s peak summer demand, even when some of the water treatment equipment needs repair or servicing.
Beyond the shift to a more resilient water source, water experts see more opportunity to boost capacity through conservation.
Maggie McHugh, an engineer with Roaring Fork Engineering, helps communities in the Roaring Fork Valley adapt to climate change.
“We can't put any more water into the system, but we can take less out,” she said. “That will be the ultimate goal, especially in years like this.”
Thanks to improvements like more efficient appliances and denser housing, Carbondale uses the same amount of water it did in 1995, despite more than doubling its population.
It’s the sort of progress that gives Wenning a bit of relief when he thinks about what climate change means for his own son’s future.
He knows he can't do anything about wildfires or smoky air, but he has agency in helping protect Carbondale’s water supply.
“At least with our water system, it may change,” he said, “But that's something I can do something about.”
