Navigating the Colorado River’s many colors
Water quality monitoring sites recently placed in Garfield County help keep an eye on sediment levels
The Post Independent
GARFIELD COUNTY — Turbidity in the Colorado River is dropping to levels previous to major wildfires and mudslides that roiled Glenwood Canyon in 2020 and 2021, Silt Public Works Director Trey Fonner said.
“But it still fluctuates heavily, the turbidity,” he said.
Whenever loose rock and dirt unearthed from heavy rainstorms barrel into the Colorado River — the main source of drinking and agricultural use for Silt, Rifle and Parachute — sediment increases. The measurement is called turbidity.
Turbidity levels rose after the Grizzly Creek wildfire consumed more than 32,631 acres within Glenwood Canyon in 2020 and after a rare, 500-year rain event in summer 2021 caused massive debris flows in the same area.
According to California-based Carollo Engineers, a firm conducting studies for Glenwood Springs in relation to the 2021 mudslides, the Grizzly and No Name creeks that feed into the Colorado River reached 8,000 NTUs.
Turbidity is measured in nephelometric turbidity units — or NTUs. These units detect the presence of suspended particles in the water.
You can see that currently in the Colorado River, which recently turned from navy blue to a chocolate-milk brown. This phenomenon is typically caused by a rush of sediment upriver.
Normal levels in the Colorado River fall at 200 NTUs or below, according to data gathered by the United States Geographical Survey agency water monitoring stations along the middle watershed. Between July 20-22, readings shot up above 600 NTUs but have since returned to below 200 NTUs.
Whenever there’s high turbidity, the town of Silt comes to mind. It’s currently trying to raise enough funds to upgrade its water and wastewater treatment center, a facility that must work harder and harder every time turbidity increases.
Fonner is directly responsible for ensuring the treatment plant properly filters Colorado River water into a clean, consumable liquid for Silt residents.
Middle Colorado Watershed Council Executive Director Paula Stepp said one of the ways to mitigate turbidity relies on new measurement devices installed up and down the Colorado River. With water quality monitoring stations established by the USGS in Garfield County, data collected from these sites are used to warn downstream users.
Though Glenwood Springs’ primary water source isn’t the Colorado River, the city has water monitoring stations at Veltus Park on the Roaring Fork River and at the confluence of the Colorado and Roaring Fork Rivers near Two Rivers Park. Three other stations are located in South Canyon, Silt and Rulison.
Say a colossal rain shower hits Garfield County, and tons of muck and mud flow into the Colorado River, public works directors like Fonner can quickly turn off Silt’s intake valve and have the city rely on its water reserves.
“Some of these water treatment plants on our Middle Colorado corridor can shut down for 24 to 48 hours,” Stepp said. “Some can only do it for a couple of hours depending on their holding and retention ponds.”
Silt’s storage tanks hold about 1.7 million gallons of water and can support town residents comfortably for at least three to four days, Fonner said. Meanwhile, in all, the town produces 400,000-500,000 gallons of water a day.
But if heavy weather events drag on for a longer period of time, town residents might notice something’s up with their water supply.
“If the higher turbidity affects us, we can’t produce as much water,” Fonner said. “We spend more time cleaning the filters, doing cleans in places or, a few months after that major event from the fire and the slide, we had to replace a whole bank of filters because it just couldn’t handle that turbidity.”
Replacing the entire bank of filters cost $50,000. Silt right now wants to improve its pre-filter mechanisms to improve water treatment and add to the capacity of its current plant. This could potentially cost between $30-40 million, so Silt officials are looking to obtain grant funding through the Colorado and Federal government.
Silt Town Administrator Jeff Layman said the town’s population was somewhere between 2,000-2,200 residents in 2003, the same year its water and wastewater treatment facility was built. The project cost about $4 million. In comparison, Silt now has 3,600 residents.
Recently, Silt used $200,000 in American Rescue Plan Act funds to pursue an engineering study on how it can better its methods of pulling water from the Colorado River. That study concluded the city needed at least $30 million to not only combat turbidity levels but better serve its growing population.
One way to pay for water and wastewater treatment improvements falls on the $1 trillion bipartisan infrastructure bill passed by Congress in November 2021.
“At least we have that going for us that there is some money out there available,” Layman said. “We’ll know a lot more about how much of that money is available for our use in probably the first couple of weeks of August.”
Stepp said elevated NTUs levels can adversely impact both water treatment as well as recreational opportunities. Joining turbidity levels are rising water temperatures, with temperatures having reached non-fishable points and causing closures up and down the Colorado.
Just last week the Colorado in Dotsero reached 75.2 degrees — at least 5 degrees higher than safe fishing conditions.
“We’re going to continue to see these fluctuations and sediments for the next few years,” she said. “Last year we had some really intense and heavy rainstorms that caused the debris flows and the damage to the highway. But that does not mean that was the end of it.”
This story is from PostIndependent.com.
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