From The Colorado Sun (Mark Jaffe):
As wildfires, avalanches and drought increase in intensity, worried city managers are planning and budgeting for better water systems and backup sources.
Communities across Colorado are…problems linked to a changing climate, from forest fires to drought. They are also already spending money on solutions to address them.
It cost Summit County nearly $88,000 to dig out from under historic avalanches in 2019 and in Carbondale the year before, low stream flows imperiled the town’s water supply spurring a $600,000 water system upgrade.
“The impacts are very real and lived and are concretely affecting communities,” said Jacob Smith, executive director of Colorado Communities for Climate Action, a coalition of 34 local governments promoting state climate policies…
At the moment, Colorado finds itself grappling with its worst wildfire season ever. Hundreds of thousands of acres burned in eight significant fires this fall, including the three largest on record, as all of the state drifted into drought status for the first time since 2013…
Over the past few decades, forest fires have been more frequent and larger in a hotter, drier West. This year’s unparalleled wildfire season Colorado coincided with the state’s warmest August on record.
Studies have shown that average summer temperatures in Colorado have risen by more than 2.5 degrees Fahrenheit since 1986. The growing heat creates drier soils, lower snowpack, earlier thaws, lower stream flows.
All those add up to increased risk of wildfires and, according to one study, added 26 days to the average fire season in the West between 1979 and 2015, a 41% increase.
There are serious risks when wildfires fires damage or destroy the watersheds towns and cities rely upon for their drinking water.
“Burned watersheds are prone to increased flooding and erosion, which can impair water-supply reservoirs, water quality, and drinking-water treatment processes,” according to the U.S. Geological Service.
The 2010 Fourmile Canyon fire, for example, burned just 23% of the watershed near Boulder, still a USGS study found that after severe thunderstorms the water heading to the city’s water treatment plant was laden with mud, nutrients and metals – some at levels four times normal.
After the High Park fire burned more than 87,000 acres in Larimer County in 2012, the Poudre River ran black after heavy rains and choked the intake pipes of Fort Collins’ water treatment plant. The water smelled and tasted like smoke.
The city now has sensors in 10 locations in the Upper Poudre to alert the treatment plan if there is a water quality problem and Fort Collins Utilities runs an average of 110 lab tests a day on its water.
Fort Collins is now “very concerned” about the Cameron Peak fire, the state’s largest fire ever, burning west of the city, Gretchen Stanford, a utility spokeswoman, said in an email…
Horsetooth Reservoir is out of commission for upgrades, leaving it only with Poudre River water. Stanford said processes are in place to deal with any water quality, odor or taste problems.
And the effects of these fires can last for years. Five years after the 2002 Hayman Fire, Denver Water was still dealing with water quality problems created by the wildfire, including a $30 million project to remove tons of sediment from the Strontia Springs Reservoir…
A warming world will create drier soils, more evaporation and more water sucked up by plants and all that led to lower stream flows, according to several scientific studies.
“There is no question that climate change is affecting stream flow,” said Brad Udall, a senior researcher at Colorado State University’s Colorado Water Institute.
Heat, not a lack of precipitation, was the key driver in a 20% decline in Colorado River flow between 2000 and 2014, compared to 20th century averages, and if the current trends continue, it will decline another 20% by 2050, according to a study co-authored by Udall.
Since 2000, the Roaring Fork’s streamflow has been about 13% lower than the 20th century average, according to a study done for Carbondale by the Western Water Assessment, an affiliate of the University of Colorado.
The study found that while there was no appreciable change in the average snow and rainfall the average temperature for the area increased 2.2 degrees Fahrenheit above the 20th century average.
That trend is projected to continue. “All climate models indicate that the climate of the Roaring Fork Valley will continue to warm well into the 21st century. Under the lower-emissions scenario, by 2050, average temperatures are projected to be 3-5°F warmer than the late-20th century average,” the study said…
The Carbondale and Glenwood Springs water projects are a sign of things to come. “What people are looking for now is redundancy, multiple sources of water supply,” Udall said. “One source, one pipeline has become a risk. It’s like betting on one stock.”
It is not only low stream flows but the timing of those flows that are presenting problems for some communities, such as Northglenn.
“Climate change isn’t going to impact Northglenn from a quantity perspective, but from a timing perspective,” said Tamara Moon, the city’s environmental manager. “The city has water rights that come into priority in the fall and rights in late May and early June. A concern is we may not have the availability of water in the fall that we have now.”
Northglenn’s worries are prompted by three trends associated with climate change: lower snowpack, earlier thaws and hotter summers. They could add up to less water in the fall.
One study led by John Abatzoglou, a University of Idaho geography professor, used 20 different climate models and federal data on snowpack to assess potential changes and projected a 5% to 20% decline in snow levels in the central and southern Rockies by 2050.
The snow season will also shorten, with more precipitation coming as rain instead of snow and earlier thaws of the snowpack, according to the study. All this could change the timing and availability of water supplies creating a need for alternative supplies or more storage.
“It is entirely possible if the runoff is early, we may not get our full quantity,” Moon said, “and in dry years we may not get the fall water.”
This scenario has Northglenn looking for ways to capture and store more water during the spring.