TVA, Community and Mother Nature Help Remove Aquatic Invasive Weeds

Fine filament, green fingers waving below the water – they belong to aquatic plants growing in rivers and lakes.

Native plants offer food and habitat for fish. But some species – including invasive hybrid "Rockstar" eelgrass, Eurasian milfoil and hydrilla – have become a nuisance on Tennessee Valley Authority reservoirs.

TVA and multiple partners fight these weeds by treating thousands of acres with EPA-approved herbicide.

They remove literal tons of them through the warm growing season.

And come winter, they let them freeze.

The combined efforts of TVA’s crews, community organizations and homeowners are paying off.

“The approximate total eelgrass debris removed was 120,000 cubic yards in 2023, 90,000 in 2024 and 70,000 in 2025,” TVA aquatic plant management program manager Stephen Turner said.

Eelgrass decline attributed to herbicide treatment and harvesting efforts by TVA's River Management team, Mother Nature and partnerships with government officials and stakeholder groups in Jackson and Marshall counties.

Stormy Weather

That huge decline is thanks to partnerships, which also include TVA’s River Management team and Mother Nature.

Each fall, TVA draws down reservoir levels to leave weeds high and dry.

“Freezing weather and seasonal drawdown help with all of the plants,” Turner said. “(The drawdown) dries them out and the winter weather freezes them.”

The water in plant cells expands as it freezes, bursting the cell walls. After a thaw, brown, dead plants remain.

In winter, when herbicide treatment is ineffective, arctic blasts and ice and snowstorms help kill swaths of lake weeds.

The benefits stretch into the next season, leading to downward trends, especially in eelgrass.

Where It All Began

TVA has helped manage shoreline weeds since the 1960s.

More recently, new challenging plants emerged.

First spotted around 2014, eelgrass mats grew to a peak on Guntersville and Wheeler reservoirs by 2023.

Eelgrass spreads in two ways: by stretching out new shoots, as strawberry plants do, and by sprouting from tiny fragments that break off when waves or boats chop up adult plants.

While TVA treats shoreline eelgrass with targeted herbicide at public use and access areas, community partners and property owners treat city and county shorelines and private docks.

TVA has worked with Mississippi State University since 2024 to study the best herbicide for the hybrid invasive eelgrass species. In 2026, they’ll begin experimental field testing.

Herbicide doesn’t work for the deep-water floating weed mats, though.

There, TVA scoops tangly plants with 10 huge harvesters, cutting boat lanes to allow for recreation, navigation and clear water flowing downstream to power plants.

As eelgrass declines, property owners and boaters may spot two other unwanted lake weeds: Eurasian milfoil and hydrilla.

Originally introduced from aquariums, pond plants and hitchhikers on boats, these weeds grow happily in TVA’s reservoirs because the climate is similar to their home range in Europe and Asia.

And all three lack any native predators to nibble their leaves and keep them in check.

Future Management

The goal isn’t complete removal of all aquatic plants.

“It’s a balanced management,” Lyn Williams, TVA fisheries and aquatic monitoring manager, said.

Native plant species are best because fish, snails, insects, ducks and other animals eat them.

Moving forward to reach balance means continued partnerships between TVA, local governments and stakeholder groups to:

• Let invasive plants dry out and freeze on drawn-down reservoir shores in winter.
• Treat weeds with EPA-approved herbicide in the growing season when plants can uptake chemicals.
• Survey, harvest and track trends over time.

An Alabama Removal Law starting in 2026 asks for homeowners’ continued help, too. Anyone removing aquatic weeds must deposit them above the high-water line, rather than flinging the plants back into the water or on others’ property.

So far, incredible success means clearer water for all who live near, play on or use the reservoir’s waters.

“It’s about balancing access and use of the reservoirs,” Turner said.