The non-native quagga and zebra mussels are wreaking havoc on reservoirs in California, Arizona, and Nevada, clogging infrastructure and substantially increasing maintenance costs.
Larvae can survive in water on boats that then infect other lakes. Annual tests show McPhee is so far negative for the mussels.
But in 2013, despite substantial prevention efforts, adult quagga mussels showed up in Lake Powell. Local water officials fear McPhee could be next because of its proximity.
Compounding the problem is Monday's announcement that the regional office of the U.S. Forest Service suddenly cut its budget for boat inspections at McPhee from $40,000 to zero for 2015. Colorado Parks and Wildlife will still contribute its $40,000 for 2015 inspections, but they are facing an operating budget that is half the usual $80,000.
"It's a real bombshell to learn this, and we are still figuring out what to do," said Ken Curtis, an engineer with the Dolores Water Conservancy District, which manages McPhee Reservoir.
From May through October, the Colorado Parks and Wildlife inspects trailered boats at the McPhee and House Creek ramps for standing water and decontaminates them before launching.
The intent is to inspect every boat to ward off contamination as long as possible. But gaps in inspection coverage make that a challenge.
Boat launches after hours rely on the honor system and public knowledge of the importance of cleaning, draining, and drying boat engines and compartments before launching and on return.
"It's a very real threat because the mussels clog pipes and valves," said Matt Thorpe, a CPW wildlife biologist. "It creates an economic disaster."
Lake Mead has spent millions of dollars retrofitting intake systems to flush out the tenacious mussel, which attaches itself in thick layers to metal and concrete substrates.
A less robust boat inspection is going in the wrong direction, officials say. If contaminated, McPhee would face higher maintenance costs to regularly remove adult mussels from canals, gates, pipes and valves.
Potentially affected water systems include Cortez and Dove Creek municipal systems, the Dove Creek canal complex, and the Towaoc Highline canal, which feeds Ute Mountain Ute farm and ranch operation. Water trucks that pull water from canals and lakes can inadvertently spread the larvae.
Studies on ways to safely kill the mussels are ongoing, including deploying a specific bacteria. So far, no solution has been found.
The filter-feeding mussels also threaten native and sport fisheries because they consume phytoplankton relied on by younger fish.
"McPhee is considered suitable habitat for these mussels," said Jim White, a CPW aquatic biologist. "It ranks at the top in the state for risk of contamination due to its proximity to infected waters."
Officials are scrambling for solutions. The budget cuts could lead to locked gates at the two boat ramps when inspection stations are closed due to shorter hours.
"Our boaters go to Powell, and most people are aware of the importance of draining, cleaning and drying their boats. We may be doing more controls at the lake," Curtis said.
According to Elizabeth Brown, CPW invasive species coordinator, the only reservoir in Colorado that is positive for quagga mussel larvae is Pueblo Reservoir.
Quagga larva was detected in Blue Mesa Reservoir, near Gunnison, but in 2014 it was declared free of the species after having no detections for five years.
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