Managing water collected from the mountain snow’s spring runoff has plenty of challenges — and will become more complex in the future due to climate change.
“As water planners, we prefer to see predictable weather patterns,” said Nathan Elder, water supply manager at Denver Water. “Unfortunately, every year is different and with climate change we’re seeing more variability and that makes it tougher to manage our water supply.”
That challenge may be most acute during runoff season, that critical — and brief — window of time when snow melts, flows into streams and fills reservoirs. Climate change may lead to changes in runoff timing that, in turn, require more nimble reservoir operations.
What’s happening?
Since the 1960s, average temperatures in Colorado have increased 2.5 degrees, according to the Colorado Water Conservation Board. That change is manifesting in significant ways.
“We’re seeing more swings between wet and dry years, more variation in year-to-year stream runoff and earlier runoff,” said Laurna Kaatz, climate program manager at Denver Water. “We’re also expecting to see more extreme weather events like extreme heat and enhanced drought, but we could also see more intense rainstorms and flooding especially if heavy rain falls on top of a lot of snow.”
Timing is everything
The timing of the snow runoff in Summit County, which is home to Dillon Reservoir, provides an example of how climate change impacts not only water collection but also recreation and flooding.
Rapid snowmelts caused by rain falling on snow could lead to a greater risk of flooding below Dillon Dam.
During a gradual runoff, Denver Water can take steps to minimize the risk of flooding below the dam, however, if there are more instances of warm weather combined with rain falling on snow, large amounts of water can fill Dillon quickly and send water through the dam’s overflow spillway. This scenario can lead to high water levels on the Blue River through Silverthorne.
“We do our best to minimize high flows out of our reservoirs, but if there is a fast runoff, we can only do so much and there’s a greater chance for flooding downstream if there’s a major rain-on-snow event,” Elder said.
Changes in runoff and precipitation also impact when Dillon Reservoir fills — or doesn’t fill — which plays a role in boating season and water levels for the Dillon and Frisco marinas.
The timing of the runoff also impacts Denver Water’s ability to make the most of its water rights.
“Later runoff allows us to use our water rights to match higher customer demand during the summer watering season,” Elder said. “Early runoff means we have to let some water go downstream before we can put it to use on the Front Range. This also impacts how much water we can store for times of drought.”
When Dillon Reservoir is full, water flows down its overflow spillway into the Blue River. Photo credit: Denver Water.
Extreme weather events
Colorado has seen several big swings in weather over the last 20 years, suggesting the kind of uncertainty that may be more pronounced as climate change intensifies and the resulting complexity in managing the snow runoff.
Most recently, the winter of 2017-2018 was exceptionally dry across the state but was followed by above average snow in 2018-2019.
The years 2012 through mid-2013 were another period of drought, followed by record flooding in September 2013. Two wet years followed in 2014 and 2015.
The dramatic weather turnaround in 2002 and 2003 is another example of how extreme weather impacts Denver Water’s water supply and planning.
Those years marked a major period of drought. In 2003, Denver Water was preparing to have water restrictions and Dillon Reservoir was more than half empty and critically low. But in March 2003, the Front Range and central mountains got hit with a major snowstorm that filled Denver Water’s reservoirs.
“A drought could last one year or several and then be followed by big snow years,” Elder said.
“We could get most of our water for the year from one or two big storms, so we have to be prepared for these situations.”
Swings in weather patterns and extreme events could have Denver Water planning for drought conditions with watering restrictions for customers and end up with a surplus of water after a big storm.
Cheesman Reservoir during the 2002 drought. Photo credit: Denver Water.
Planning for climate uncertainty
Denver Water has relied primarily on historical weather patterns and data to plan for how much water it will collect from mountain streams. Now the utility is incorporating climate change into its long-range preparation through scenario planning.
“One component of scenario planning involves creating a variety of potential climate scenarios instead of simply assuming patterns will stay the same over the next 50 to 100 years,” said Jeff Bandy, a water resource manager at Denver Water. “This approach helps us plan for potential changes in climate and evaluate our system’s reliability.”
Denver Water takes data from global climate models and uses the information to create various outcomes on streamflow and precipitation in its water collection system.
The planning team develops scenarios that include variables such as warmer temperatures, more precipitation and shifts in timing of precipitation, all of which result in changes to volume and timing of runoff in Denver Water’s watersheds.
“We evaluate the scenarios and determine if future infrastructure projects or operational changes are needed,” Bandy said.
Denver Water collects water from 4,000 square miles in Colorado’s central mountains and foothills. With such a large area, getting accurate and timely information about weather and streamflow conditions is critical to water supply management.
“We use a lot of different data sources to manage and forecast water supply and a lot of these data sources are based off historical climate data,” Elder said. “With a changing climate, the current data sources are no longer as reliable as they used to be. This makes it more difficult to manage our reservoirs.”
In preparation for more weather extremes and variability, Denver Water has begun investing in new technology to get a more accurate picture of the snowpack above Dillon.
Looking to the south from a plane above Dillon Reservoir in June 2019, during an Airborne Snow Observatory flight to gather data on the snowpack above the reservoir for Denver Water. Photo credit: Quantum Spatial.
“In April 2019 we used NASA’s Airborne Snow Observatory, which uses a plane, to measure snowpack over the mountains in our watershed,” Elder said. “The more we know about the snow, water content and runoff, the better decisions we can make when it comes to managing our water supply for our customers and the communities where our reservoirs are located.”
Nathan Elder, Denver Water’s manager of water supply, tracks a variety of factors to keep tabs on the snowpack and water supply. Photo credit: Denver Water.
What can customers do?
The best way communities can be prepared for the impacts of climate change is to use water wisely.
“Our water supply is vulnerable to climate and our customers play a major role in how we manage our system,” Elder said. “That’s why we always ask our customers to be efficient with their water all year long and even in wet years.”
Water is a limited resource in Colorado so climate change will impact communities on both sides of the Continental Divide.
“Climate change means water change and that’s important to us all,” Kaatz said. “So, it’s our goal at Denver Water to make sure we’re thinking about it and actively preparing for the changes we’re going to experience.”
The Fountain Creek Watershed is located along the central front range of Colorado. It is a 927-square mile watershed that drains south into the Arkansas River at Pueblo. The watershed is bordered by the Palmer Divide to the north, Pikes Peak to the west, and a minor divide 20 miles east of Colorado Springs. Map via the Fountain Creek Watershed Flood Control and Greenway District.
One of the Pikes Peak region’s largest real estate development companies is planning thousands of homes on roughly 5,600 acres on Fountain’s east edge, but it might take Colorado Springs’ water to transform the prairie.
La Plata Communities had banked on Fountain to provide at least some of the water necessary for a new company development, known as Amara; a southern portion of the property, the Kane Ranch, was annexed by Fountain in 2008.
Now the company is asking to remove, or de-annex, the 2,400-acre Kane Ranch from Fountain’s boundaries, likely in favor of requesting Colorado Springs to annex the land.
The company framed its need to leave Fountain as a failure of the city to plan ahead for future water needs, according to documents La Plata submitted to the city. Fountain officials say they are facing unprecedented demands on the city’s water system and could not have anticipated so much growth at once.
The unusual de-annexation proposal by La Plata Communities — the Springs-based developer of Briargate, a master-planned residential and commercial development that covers 10,000 acres on the city’s north side — underscores water’s importance as the lifeblood of development in the Pikes Peak region.
In an arid climate where water is precious, developers who don’t have it can’t do business. And that’s why Colorado Springs and its vast water resources have always been appealing.
Colorado Springs Utilities is planning to serve nearly 54% more people — an increase from 470,000 to 723,000 — in the next 50 years. The agency has developed an extensive plan that includes new reservoirs, water reuse and conservation to meet future needs.
Some of the hundreds of thousands of new residents could move into new subdivisions to the city’s north, east and south.
A city of Colorado Springs map shows 158 square miles that the city would consider annexing for new development. The map is not a commitment to annex those properties, but it does help guide decisions, Planning and Community Development Director Peter Wysocki said.
A large portion of La Plata Communities’ new Amara development is considered an area Colorado Springs would annex and it would make sense for the whole project to be annexed, if the city determines it can provide services to it, Wysocki said.
The proposed Amara development is composed of two areas.
The 3,200-acre Tee Cross Ranch Properties lies in unincorporated El Paso County, east and north of Fountain; the late rancher, developer and philanthropist Robert Norris, known as the Marlboro Man because of his appearance in advertisements for the cigarette brand, owned the property as part of the more than 95,000 acres he controlled in the county.
The 2,400-acre Kane Ranch, south of Squirrel Creek Road, is within Fountain’s boundaries and at the heart of La Plata’s frustration outlined in a fiery petition the company submitted seeking to remove it from the city’s boundaries…
Fountain’s decision to ask the developers to bear the costs of infrastructure development and water storage also was “unworkable,” it said…
Fountain has faced a flood of developer requests to build — together representing 30,000 new homes across 24 projects in 14 months — more than it could immediately serve, said Todd Evans, Fountain’s deputy city manager…
It would be like the city of Colorado Springs trying to expand from 600,000 taps, or buildings needing water service, to 1.8 million, he said.
Demand just from the Kane Ranch property would have represented 25% of the demand of the city’s entire system, Fountain Utilities Director Dan Blankenship said…
The Fountain City Council will decide in the coming months whether to grant La Plata’s de-annexation request and return the Kane Ranch to El Paso County’s jurisdiction. If the property is removed from Fountain’s city limits, La Plata could ask for annexation by Colorado Springs.
Colorado Springs already is weighing the annexation of a northern portion of Amara and a decision on that parcel is possible in 2022, Wysocki said.
Nathan Bell, a consultant with the Silt Water Conservancy District points to the sediment built up where the canal that takes water from the Colorado River feeds into the pump house. An upstream water quality monitoring project, which received funding approval from the Colorado Basin Roundtable, could help alert the district when mudslides occur in Glenwood Canyon. CREDIT: HEATHER SACKETT/ASPEN JOURNALISM
Water managers are dealing with the after effects of the Grizzly Creek Fire and subsequent mudslides in Glenwood Canyon by continuing a water quality monitoring program.
The Middle Colorado Watershed Council received funding approval this week for the second phase of a program that will continue to collect and distribute data about weather and river conditions downstream of the Grizzly Creek burn scar. The Colorado Basin Roundtable approved $72,200 in state grant money for continued data collection at seven rain gauges in Glenwood Canyon, which will provide information to the National Weather Service, an automatic water quality sampler, soil moisture sensors, a new stream gauge and water quality monitoring station in the Rifle/Silt area and a data dashboard for easy access of the information.
The first phase of the project, which was implemented early last summer before the monsoons, addressed immediate water quality issues, collecting data at the rain gauges every 15 minutes.
The second phase of the project amounts to an early warning system that will let water users downstream of Glenwood Canyon know when dirty water from mudslides is headed their way. The MCWC hopes to have all the pieces in place before spring runoff.
“With the way post-fire events happen, we are going to be looking at impacts for the next two to five years,” said Paula Stepp, executive director of the Middle Colorado Watershed Council. “The part I’m really excited about is the cooperation between stakeholders and downstream users.”
On July 29, a heavy rainstorm triggered mudslides in Glenwood Canyon, which left some motorists stranded overnight, and closed Interstate 70 for weeks. Because soils scorched by the 2020 Grizzly Creek Fire don’t absorb moisture, the rain sent rocks, sediment and debris flowing down drainages, across the highway and into the Colorado River.
But the mudslides didn’t just affect the river at the site of the rainstorm. The cascade of dirty water also had impacts to agricultural and municipal water users downstream in Silt, whose only source of water is the Colorado.
The sediment-laden water caused problems for the town of Silt’s water treatment plant, which had to use more chemicals to get the sand to settle out. The increased manganese and iron suspended in the water gave it a brownish tint at taps. It also fouled a set of filters, which the town spent $48,000 to replace. The filters normally last four to five years, but had to be replaced after just one, said Trey Fonner, public works director for the town.
“If we knew what was coming down the river, we could shut off the intake and we could let the river clean up a little bit before we turned it back on,” Fonner said. “If our tanks are full, we can shut off and let the worst part of it go by.”
Town of Silt Public Works Director Trey Fonner points out how the water treatment plant’s filters were affected by turbid water from the mudslides in Glenwood Canyon last summer. The town had to replace them at a cost of $48,000. CREDIT: HEATHER SACKETT/ASPEN JOURNALISM
Conservancy district impacts
The mudslides also created challenges for the Silt Water Conservancy District, which delivers water from the river to about 45 headgates via a canal and pumphouse. Although the town can temporarily shut down its intake because it has about a three-day supply of water in storage, the conservancy district pumps water continuously and shutting off for a brief period of time is difficult.
“It’s not really a system that can be shut down easily,” said Nathan Bell, a consultant for the district and roundtable member. “It’s extremely cumbersome. It’s a nightmare.”
The main problem for the district is that the earthen canal which takes water from the river to the pump station silts up. The turbid water also acts like sandpaper, causing more wear and tear on the machinery and reducing its lifespan. The district is planning on more frequent canal cleanings and installing drop structures to catch the mud before it makes it to the pump house.
The data generated from the monitoring project will allow the district to better plan and budget for the inevitable increased maintenance and repairs, Bell said.
“It reduces the variables you’re having to manage,” he said. “It lets us get ahead of the game.”
The data dashboard will let downstream users and the general public set up text alerts for when a parameter of interest is too high or outside a specific window. Silt water users, for example, could set an alert for when rain gauges in Glenwood Canyon record a certain amount of rain, which increases the likelihood a plume of dirty water is headed their way.
The total cost of phase two of the project is nearly $1.3 million. The watershed council is asking the Colorado Water Conservation Board for about $650,000 in grant money and they also expect funds from the U.S. Geological Survey. Garfield County has committed to $15,000 over the next three years and the Colorado Department of Public Health and Environment will contribute $50,000.
Aspen Journalism covers rivers and water in collaboration with The Aspen Times. This story ran in the Dec. 4 edition of The Aspen Times and the Glenwood Springs Post-Independent.
