Grand Valley water managers plan to eradicate invasive species

Grand Valley water managers have a plan to nip a potential zebra mussel infestation in the bud: An irrigation district began treating its water this fall.

Authorities hope to get federal funding to treat the water that irrigators and water utilities take from the Colorado River with liquid ionic copper, which kills zebra mussels. Mesa County plans to apply for the money through the U.S. Bureau of Reclamation's Bucket 2 Environmental Drought Mitigation program.

Microscopic zebra mussel larvae, also called veligers, were found this summer in the Government Highline Canal, a critical part of the irrigation infrastructure for the Grand Valley's agricultural producers. If this invasive aquatic species becomes established, it could have devastating consequences for farms, vineyards, orchards and Colorado's famous Palisade peaches. Native to Eastern Europe, the rapidly reproducing mussels can clog water infrastructure and are incredibly difficult to eradicate once established.

“Our concern is for our smaller partners,” said Tina Bergonzini, general manager of the Grand Valley Water Users Association. “Many of our commercial peach growers and wineries use micro-drip irrigation. It would cost absolutely nothing to shut down those systems completely, and that would be catastrophic. … Depending on the extent of the infestation, it could completely cripple agriculture from Palisade to Mack.”

Mesa County plans to apply for over $4 million in grants on behalf of irrigation districts and water utilities. This will come from the remaining $450 million in Inflation Reduction Act funding for projects in the upper Colorado River basin (Colorado, New Mexico, Utah and Wyoming). The so-called “B2E” grant is for projects that provide environmental benefits or ecosystem restoration and must be awarded to public entities or tribes. Several irrigation districts and inland water utilities would participate in the copper treatments: GVWUA, Grand Valley Irrigation Company, Orchard Mesa Irrigation District, Palisade Irrigation District, Mesa County Irrigation District and Clifton Water.

“Mesa County recognizes the serious threat posed by the recent discovery of zebra mussels in the Colorado River and Government Highline Canal,” Mesa County Commissioner Bobbie Daniel said in a written statement. “We understand the urgency of the zebra mussel situation, and that is why Mesa County is leading the charge in applying for federal funding to combat this problem.”

The Palisade Irrigation District is not waiting for federal funds. It plans to begin copper-treating the eight-mile-long Price Ditch and its numerous tributaries this fall, which irrigate about 5,000 acres of orchards, vineyards, alfalfa, corn fields and lawns. The PID gets its water from the Government Highline Canal.

PID Superintendent Dan Crabtree became aware of the problems with quagga mussels, a species related to zebra mussels that causes similar problems, during his annual trips to Lake Powell. He knew the mussels could one day become a problem in the Upper Basin.

“It just seemed inevitable that we were going to get them here somehow,” Crabtree said. “The Palisade Irrigation District actually set up a line item in our budget about four years ago for this very thing, so we set some money aside. In my opinion, our system is very vulnerable to mussels because we're all pipes.”

Crabtree said PID plans to begin copper treatment in October, which will cost the district about $60,000.

Water utilities in the lower Colorado River (Arizona, California and Nevada), including the Central Arizona Project, have used copper to kill invasive mussels that threaten infrastructure. Experts say the treatment does not harm fish or crops.

“We're taking advantage of the fact that zebra mussels are very, very sensitive to copper, even at low parts per million,” said David Hammond, senior scientist at Earth Science Labs, which makes the liquid ionic copper under the brand name EarthTec QZ. “I certainly understand that people are cautious about pesticides and want to make sure they've been tested and are being used wisely, and I share that view. This is very safe for people and food.”

GVWUA flew Hammond from California to look at the infrastructure and advise them on how to develop an action plan.

“It looked alarmingly fragile,” he said. “Almost everywhere you looked there seemed to be areas of concern.”

Focus on prevention

In August, Colorado Parks and Wildlife staff provided an update on zebra mussels at a meeting of the state legislature's Water Resources and Agriculture Review Committee. Robert Walters, manager of CPW's Invasive Species Program, told lawmakers that non-native mussels are the most costly invasive species in the United States and are the highest priority for the state's invasive species program.

“Once they're established, eradication is almost impossible,” Walters said. “We're really, really focused on prevention. It's really, really difficult to remove them, so we want to do everything we can to keep them out in the first place.”

Walters says there are three characteristics that make zebra mussels extremely harmful: They reproduce prolifically, with a single female capable of giving birth to a million young a year; they attach themselves to hard surfaces with a thread called byssus that acts like an anchor, making them difficult to remove; and they can each filter up to a litre of water a day, removing the plankton and nutrients that form the basis of the food web, which could lead to the collapse of fish stocks.

Mussels have been discovered in several Colorado lakes since 2008, but adult mussels were not found until 2022 in Highline Lake at the northwest end of the Grand Valley. Highline Lake was treated with liquid ionic copper in March 2023.

In July, the mussels were found during testing at two other locations in the Colorado River: the Blue Heron boat ramp in Grand Junction and the Beavertail Mountain Tunnel exit, just upstream from the Cameo diversion in DeBeque Canyon. Where the mussels came from is still unclear, but authorities suspect it could be a small lake or pond upstream.

“Our focus now is really on surveillance,” Walters said. “We really, really want to know where these are coming from and how far this population extends.”

In addition to continually collecting water samples, CPW staff are doing everything they can to educate the public about the severity of the problem and what people can do to prevent the spread to other bodies of water, such as cleaning and drying their gear. Walters said officials have contacted 164 outfitters who use that stretch of river and spoken to more than 3,000 people who recreationally use the river. CPW and its partners also have 77 boat inspection sites across the state and conduct more than 500,000 watercraft inspections annually, Walters said.

So far this year, 35 boats carrying mussels have been intercepted at the Loma port of entry. The decontamination process involves spraying the boat with 60-degree water for 10 seconds, which kills the mussels. They are then removed from the boat using a high-pressure cleaner.

Applications for the federal B2E grant must be submitted by Oct. 14. Even if Grand Valley water users are approved for the money, they probably won't get it for about a year, Bergonzini said. That means they'll have to be extra vigilant about the mussels during another irrigation season.

“We're also trying to make sure we keep testing our channels to see if we can find anything else,” she said. “It's like a really frustrating game of hide and seek. You don't want positive results, but then when you don't get positive results, it's so frustrating because you're like, 'Where are you?'”

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