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Inspectors At Ruedi Reservoir First Line Of Defense Against Growing Threat Of Invasive Mussels

Jul 29, 2020

An inspector from Rocky Mountain Recreation begins the process of a boat inspection at Ruedi Reservoir. So far this year, twelve boats at Ruedi have been found to have invasive quagga and zebra mussels. The species disrupt the aquatic food chain and clog intake pipes for water-related facilities and boat engines.
Credit Christin Kay

On a recent busy Saturday morning at Ruedi Reservoir in the Fryingpan River valley, Jaime McCullah sprayed a high-powered jet of hot water over every nook and cranny of a bright-green motorboat. 

McCullah is a supervisor for Rocky Mountain Recreation, which inspects boats at Ruedi for quagga and zebra mussels. She found mussel shells, smaller than a fingernail, on the craft she just decontaminated. 

Last year at Ruedi, inspectors found mussels on six boats. This year, since the boat ramp’s opening June 1, inspectors have already found mussels on 13. The increase, a concern for local water officials, is an indication of a growing invasive-species problem throughout the Colorado River basin.

April Long, director of the Ruedi Water and Power Authority, said the increase in boats with mussels is concerning, especially because if they take hold and multiply, they could damage the infrastructure that supports the dam at Ruedi. Once introduced, mussels can quickly clog water distribution and the outflow systems of dams.

“They would attach to those, and it would be very difficult to claim to remove them,” Long said. “And so then they could affect the operation of the dam.” 

But the resources that could be affected aren’t just at the reservoir itself. 

The water released from the dam flows into the lower Fryingpan River’s gold-medal trout fisheries, an important part of the valley’s outdoor-recreation economy. It also powers a hydropower plant operated by the city of Aspen. Ruedi water is also sent downstream to what’s known as the 15-Mile Reach of the Colorado River — a vulnerable section near Grand Junction — to assist in the recovery of endangered fish.

If mussels got into the dam at Ruedi and affected streamflow in the Fryingpan, Long said, all of those concerns would be impacted.

“They could affect every little aspect of why we love the reservoir, why we use it,” she said.

Ruedi Reservoir was built as compensatory storage for Western Slope water users as part of the Fry-Ark Project. Upstream of Ruedi, through the Boustead Tunnel and Busk-Ivanhoe Tunnels, the project diverts about 59,000 acre-feet of water a year to communities such as Colorado Springs, Aurora and Pueblo.

Invasive mussel species are already prevalent in areas popular with Colorado boaters, including Lake Powell in Utah, but currently, there are no waters infested with mussels in Colorado. Officials say the state’s rigorous inspection program, which includes Ruedi, is key to protecting the state’s outdoor recreation and water-supply infrastructure. 

Samples of zebra and quagga mussels found on watercraft at Ruedi Reservoir over the Fourth of July holiday. So far this year, mussels have been found on boats that have recently visited Lake Powell, where the invasive species run rampant.
Credit Christin Kay

Aquatic Nuisance Species Program

Colorado’s aquatic nuisance species (ANS) program began in 2008. The program requires boats to be inspected when they’re going into and coming off many Colorado reservoirs. When Ruedi’s boat ramp is open — which in the summer is from 6 a.m. to 10 p.m. daily — inspectors carefully watch boats coming and going. And Colorado Parks and Wildlife monitors the reservoir itself through monthly testing of water samples that would detect the presence of mussels. 

Even over the Fourth of July weekend, the three inspectors on site can check boats efficiently enough to avoid long lines. McCullah said the majority of boaters are cooperative and want to help protect lakes and reservoirs. 

The inspection program costs about $70,000 to staff during the peak months of May through August, with funds provided by Ruedi Water and Power Authority entities, as well as the Colorado River Water Conservation District and Grand Valley domestic water provider Ute Water, both of which store significant amounts of water in Ruedi Reservoir. Colorado Parks and Wildlife provides $25,000 for the program in the months of September and October. 

The 13 boats found with the unwelcome hitchhikers at Ruedi since June 1 came from Lake Powell, which has a severe mussel infestation and is the source of many of Colorado’s boat contaminations. That means anyone who comes from Lake Powell gets what’s called a “high-risk inspection.” Inspectors carefully comb through the engines, wheel covers and bilges. 

“Mussels like dark, wet, 90-degree angles,” McCullah said. “That's an entire boat.”

If mussels are found, or if there’s standing water anywhere that could contain larvae, known as veligers, the boat gets decontaminated with a thorough spraying of 140-degree water. Ropes, anchors, water skis, life jackets and anything else that has gone into waters where invasive mussels are present gets hosed, too. This can take anywhere from 2½ to three hours. 

“If (the boaters) don’t understand the program, they just think it’s a carwash,” McCullah said.

Boats qualify as low risk if they have a seal from a state of Colorado inspector that shows it passed inspection the last time the vessel was in the water. Provided they are not carrying any live bait on the craft, the boaters are able to proceed to launch after registering and speaking with an inspector. 

Colorado’s ANS inspections are more thorough than many neighboring states, and officials say that is what’s needed to stop a rapidly growing threat to the state’s water supply. That makes the ANS program at places such as Ruedi a critical first line of defense. 

"When you're talking about millions and millions and millions of mussels, then they are filtering millions and millions of liters of water per day and removing the basis of the aquatic food web."

‘They Are Uncontrollable’

Zebra and quagga mussels were brought to the U.S. on shipping vessels from Eastern Europe. The invasive species were first found in the Great Lakes in the late 1980s. The first detection of a quagga mussel west of the Continental Divide occurred at Lake Mead in 2007. 

“Since then, they've completely taken over Lake Mead and have spread to some of the other Western waters, including Lake Powell, over the last 10 to 15 years,” said Robert Walters, an invasive-species specialist with Colorado Parks and Wildlife. 

Utah’s inspection program requires boats to be checked when they leave Lake Powell. However, Walters said, due to the high volume of boats coming and going, inspections at Powell aren’t fail-safe. 

“They’re doing the best they can,” he said. “But they did over 100,000 inspections last year, and a lot (of those boats) have mussels.”

The invasive species can alter the ecosystems of lakes and reservoirs. The water at Lake Powell has grown more crystal clear in recent years, but that’s not a good thing, Walters said. Zebra and quagga mussels are known as “filter feeders,” removing plankton from water. Each mussel can filter up to a liter of water daily. 

“Which may not sound like a lot,” Walters said, “but when you're talking about millions and millions and millions of mussels, then they are filtering millions and millions of liters of water per day and removing the basis of the aquatic food web.” 

The removal of plankton can cause a chain reaction, not only leaving little food for native species but also allowing sunlight to penetrate deeper in clearer water, which raises the temperature and forces native fish deeper. 

In addition to their ecological impact, zebra and quagga mussels have characteristics that make them particularly threatening to water infrastructure. For starters, Walters said, they’re extremely prolific reproducers. A single female mussel can produce up to a million eggs annually. 

“If even one became established in one of our lakes or reservoirs, then, at a million per year per mussel, that population would have the potential to expand extremely quickly,” Walters said. 

The mussels also have thread-like appendages that form chemical bonds to rocks and other surfaces, making them difficult to remove. 

While invasive mussels could clog the dam’s infrastructure at Ruedi, April Long, director of the Ruedi Water and Power Authority, said they could also hurt recreation at the reservoir. “They could affect every little aspect of why we love the reservoir, why we use it.”
Credit Christin Kay

A Growing Threat

So far, just one reservoir in Colorado — Standley Lake in Westminster — has limited boating access because the threat of invasive mussels is too great to infrastructure. Long said closing Ruedi to boaters hasn’t been discussed at this point. 

“But,” she said, “I can imagine that that could be part of the picture if we were trying to protect those resources.”

Long and Walters said if boaters are responsible and comply with inspections, the dangers posed by zebra and quagga mussels are manageable. And over the past few years, they said boaters have become better educated and more cooperative with investigators at Ruedi. 

However, Long said that more resources could be needed for the ANS program in coming years to avoid long waits for boaters.

“I think,” she said, “that we have to grow as the threat grows.” 

This story was produced by Aspen Journalism - a local, nonprofit, and investigative news organization collaborating with Aspen Public Radio on coverage of environmental issues.