Report: Invasive Plants a Concern for Reston

While the overall health of Reston's lakes are good, there is concern over invasive plant species in and around the water.

That is the finding of a report by Aquatic Environmental Consultants (AEC), which has been testing and analyzing lakes for 14 years.

Bill Kirkpatrick, president of AEC, says RA Lakes are monitored six times annually, April through September.  

"You are doing a good job with water quality," he told RA's Board of Directors at a recent meeting. "The real concern I have is the invasive plant species. They are idiot-proof - people can't kill them. Then you put them in the lake and I can't kill them. I see that as a real concern."

Among the invasive plants:

Eurasian Water Milfoil, Yellow Floating Heart (both non-native invasive plants) and Floating Leaved Pondweed at Lake Thoreau.

The Floating Leaved Pondweed is native and is typically a beneficial plant for fish habitat and waterfowl food. The Eurasian Water Milfoil is non-native plant that is of high concern.

in June. So far, the results have been positive, RA says. The herbicides used were Renovate Max G, Aquathol-K, and Clean Amine.  

RA is continuing with an algae-treatment program at Lake Anne  consisting of a series of copper sulfate (algaecide) treatments at low concentrations to control algae blooms. Copper sulfate is commonly used in drinking reservoirs to control blue green algae.  

Kirkpatrick said he suspects that some of the invasive species began in homeowners' yards and then moved into the lakes. RA Parks and Recreation Director Larry Butler said eradicating the yellow floating heart at Lake Thoreau has already gone over budget this year.

"I think someone very close to Lake Thoreau has a water garden in their yard," said Kirkpatrick. "As more species show up, you should budget more [for getting rid of] them."

Overall, Lake Thoreau has the most favorable water quality, said Kirkpatrick, followed by Lake Anne and Lake Audubon. Lake Newport, which is the “youngest” lake at around 23 years old, has shown a decrease in overall water quality and will be the subject of more thorough review of management strategies in the future, RA said.

Lakes Thoreau and Newport have seen a large growth in aquatic plants this year. Too much growth of aquatic plants can decrease aesthetic and recreational benefits, particularly boating. Some aquatic plant growth is beneficial as it provides habitat for fish and other aquatic life, and photosynthesis provides oxygen to the water column, Kirkpatrick said.

Kirkpatrick said water quality general goes down in the summer but improves with the cooling of the water in fall.

To see the complete report, click here.

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