Scientists working to control invasive weeds along the Truckee River | SierraSun.com

Scientists working to control invasive weeds along the Truckee River

Josh Staab
jstaab@sierrasun.com

TRUCKEE, Calif. — It's still not entirely clear how it got there in the first place, but area scientists and residents have just about had it with the ever-increasing spread of an invasive plant that's taken root along the Truckee River.

Eurasian watermilfoil, a plant native to areas of Europe, Asia and North Africa, has had widespread impact in North America since reports of its negative impact started becoming prominent in the early 1940s.

Here at Tahoe-Truckee, however, it wasn't until the 1980s that scientists started actively identifying the noxious weed for control and eradication.

Dan Shaw, an environmental scientist with California State Parks, first became entangled with watermilfoil when he began work on eliminating about six acres of it from Lake Tahoe's Emerald Bay.

Control strategies used there included laying down bottom barriers, like large pieces of plastic sheeting, to kill the plants by eliminating light.

That effort began in 2010 and lasted until the latter part of 2014, when he and crews felt the area was thoroughly purged of the persistent weed. He and others still go back periodically to eliminate new growth as it sprouts.

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ONTO THE TRUCKEE RIVER

Working with the Tahoe Resource Conservation District, Shaw hopes his work in Emerald Bay will lend itself to efforts along the Truckee River's shores.

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READ MORE: Scientists, locals partner to combat Lake Tahoe's invasive species.

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According to TRCD, the plant likely entered the river following the overflow of the Lake Tahoe Dam in Tahoe City in 1997 and has been more prolific the last five to seven years.

Unlike most lakes, the river's running waters add challenges to the control process, Shaw said, even during the current drought period when its levels are so low.

However, it's the water's low level TRCD crews believe will offer new opportunities to perform control measures, said Kim Boyd, district manager at TRCD.

"With the drought conditions, many people have asked how the lack of water at the dam and down the Truckee River will impact efforts to remove invasive plants," Boyd said. "With the low waters, this creates a unique opportunity to use bottom barriers which provides a cost-effective technique for plant removal."

During an Aug. 24 check, U.S. Geologic Survey officials gauged Truckee River's flow at about 1.3 cubic feet per second. Historically, the river has run as high as 2,360 cubic feet per second.

Like efforts made to eradicate the milfoil from Emerald Bay, Mollie Hurt, TRCD director of programs, is hoping to use similar large plastic panels to act as sun shades, depriving the sun-thirsty weed of one of its primary energy sources.

While the Truckee River is known for periods of fluctuating water level, its low levels made it a convenient time for crews to test fixing the panels to some of the river's more affected areas, Hurt said.

"We fielded a lot of questions because it looks very unusual," Hurt said.

ADAPTING TO DRIER CONDITIONS

The process involves taking the large plastic sheets, placing them over the affected areas, and anchoring them in place.

In a river environment, that process becomes slightly more problematic, Hurt said, so crews opted to use the river's own rock features to affix the sheets.

In October, when the sheets are removed, the team will assess progress and make decisions based on the river's water level and the status of the milfoil.

Hurt said it's still somewhat unknown how fluctuating water levels impact the milfoil's growth, or the barriers ability to stat intact.

"The success of the method is going to depend on how well (the barriers) work in certain water conditions," Hurt said. "When you have a water year when flows are higher, I'm not sure if barriers would be the best to use, because high water might make it hard for the barriers to say in place."

Shaw points out before the completion of the Tahoe City dam in 1913, the Truckee River had large portions go dry toward the end of the summer season.

"This means the native plants and animals were probably well adapted to drier conditions," Shaw said. "Milfoil doesn't react the same way as those plants."

Shaw noted the area rife for infestation extends from the dam down river as far as the River Ranch in Alpine Meadows, and possibly beyond, which is why addressing the problem upstream and working down is a good strategy.

'IMPORTANT TO OwUR COMMUNITY'

One thing Shaw and Hurt agree on is the project will require a periodic return to the affected areas regardless of the success of this current attempt.

TRCD anticipates the need to continue efforts for several years along the river, as the population is denser in some locations versus others.

With some of the densest areas of growth near some of the river's more popular destinations, Hurt said efforts to control the growth will get higher priority based on visitor frequency level, but ecological impact will not be ignored.

"Prioritization is based on ecological impacts," Hurt said. "There is some sensitivity to the prioritization list; it shows generally the areas of greatest need."

The Community Foundation of Western Nevada/Truckee River Fund, the California Department of Parks and Recreation, the Tahoe Fund and the Rotary Club of Tahoe City have provided funding for the project.

"The Truckee River is important to our community as well as our visitors," said Patti Boxeth, board member of the Rotary Club of Tahoe City, heading up community service initiatives. "We just can't ignore taking advantage of something so big."

While Boxleth felt a monetary contribution was necessary, she noted how important it is as a community member to provide the service as well.

"We give money, but we also like to do hands-on projects," she said. "We want to participate in the process, and if we have to get our boots on, we will do that."

More online

Visit http://www.tahoercd.org for information on the Tahoe Resource Conservation District and about aquatic invasive species.

Visit invasivespeciesinfo.gov/aquatics/watermilfoil.shtml to read more about Eurasian watermilfoil.