Progress made in eradication of Truckee River invasive plant
November 27, 2017
Tahoe Resource Conservation District is three years into a long-term aquatic invasive species eradication project on the Truckee River — and the progress is encouraging.
TRCD is working to eliminate Eurasian watermilfoil from a 3-mile stretch of the Truckee River, starting above the Tahoe City dam and continuing down to Alpine Meadows Road.
"The results are kind of mind-blowing," said Nicole Cartwright, TRCD executive director. "We were seeing densities where there could have been 50 percent coverage with aquatic invasive plants. After one year of treatment, the following year we're coming back and there are little tiny plants scattered throughout with less than 10 percent coverage. So the treatment has been very effective, it's just slow at this point."
Treatment includes a combination of bottom barriers — which cut off oxygen and sunlight to the plants — and diver-assisted suction removal.
Cartwright said that fragments of Eurasian watermilfoil likely traveled from the south end of Lake Tahoe, where it's predominately concentrated, to the Truckee River after flooding in 2006.
"Over a 10 year period we've seen really great establishment and pretty remarkable coverage actually," said Cartwright. "The root structure in the river is very different than in the lake. Where we have removed patches of Eurasian watermilfoil, it's almost like they are creating their own microclimates."
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The usually rocky riverbed is covered in silt held in place by the root systems. Upon removal, the silt is washed away and the riverbed is restored to its original condition, which provides a habitat for native fish and mussels.
But the project could take another 10 years to complete.
"If we were able to get designated funding to get divers and hand crews out there seven days a week for three months, that would look a lot different, but we just don't have that kind of funding, so we're biting off little chunks at a time. It's a tiny window when recreation has been completed — all the river rafting has stopped or is slowing down — to when the snow flies," explained Cartwright.
"In that timeframe we're still dealing with low-water levels or high flows. It's a dynamic system and that makes planning for the project very difficult."
Current funding for the project comes from a variety of agencies, including California State Parks, Tahoe Fund, Tahoe City Rotary, Truckee River Fund and the Department of Water Resources.
Meanwhile TRCD is preparing to release preliminary results from its invasive species pilot project at the Lakeside Marina and Beach this summer. A private firm hired by TRCD made progress in eradicating Eurasian watermilfoil using targeted ultraviolet-C light administered from a boat fitted with a drop-down panel of lights. The research showed that UVC light damaged the DNA and cellular structure of the plants, causing them to die.
"We have one year of post-monitoring to do, so this next summer season we will do biological and water quality post-monitoring," said Cartwright. "The final conclusion will come out next December."