Stay away! Water samples collected at several sites indicate harmful bacteria not safe for swimmers.

A health advisory has been issued for Lake Anna due to several positive tests for harmful algae bloom (HAB). The state recommends avoiding these areas until the algae concentrations have returned to an acceptable level.

How does harmful algae bloom occur?

Algae is a microorganism that occurs naturally in saltwater and freshwater environments around the world. In its normal state, it doesn’t pose a threat to people or animals. It’s actually quite helpful, as it provides food, nutrients, and protection to marine plants and animals. The problem happens when the growth gets out of control, causing a “bloom.” This happens in warm, still water with lots of nutrients like nitrogen, phosphorous, and iron. In saltwater conditions, this is known as the red “tide” that occurs along the Gulf Coast of Florida.

What risks are associated with HAB?

The harmful algae, called cyanobacteria, can cause skin rash and gastrointestinal conditions such as nausea, vomiting, diarrhea, and upset stomach in people and pets. It can also kill fish and plants in the water.

Here are the Lake Anna areas under advisory for harmful algae bloom:

Pamunkey Branch

  • Upper – from the upper waters of the Pamunkey arm and downstream to the confluence of Terry’s Run
  • Terry’s Run – from the upper waters downstream to the confluence with Pamunkey Creek
  • Middle – from the confluence with Pamunkey Creek to Route 612 (Stubbs Bridge)

North Anna Branch

  • Upper – From the upper waters of the North Anna arm downstream to the Route 522 bridge

Water samples collected at these sites indicate harmful bacteria that exceeds safe swimming guidelines. All types of watersports and activities—including fishing, swimming, kayaking, stand-up paddleboarding, and skiing—that could involve ingesting water are not recommended. Advisory signs will be posted along the lakefront. Routine monitoring and sample collecting are being done in the Route 208 area.

Lake Anna algae

Lake Anna's harmful algae bloom in 2018, courtesy of WTOP

How to avoid HAB

  • Avoid foamy, scummy, and discolored water that is green or bluish-green (they’re more likely to contain toxins).
  • Don’t allow pets or children to drink from lakes and other bodies of water.
  • If you do come into contact with water, rinse off with fresh water as soon as possible (including pets).
  • If anybody (including pets) experiences symptoms, seek medical attention.
  • Contact the Virginia Harmful Algal Bloom Hotline at 1-888-238-6154 if you have experienced health-related effects.
  • Visit to learn more.

The Virginia Harmful Algal Bloom Task Force, which includes the Virginia Department of Health, the Virginia Department of Environmental Quality, and the Old Dominion Phytoplankton lab, will continue to monitor the water quality and safety at Lake Anna. Once there are two consecutive test results with acceptable levels, the advisory will be lifted.

Lake Anna is the third largest lake completely within Virginia (Kerr Lake is the largest, but it shares space with North Carolina). Located in Louisa, Spotsylvania, and Orange counties, the man-made lake is a popular destination for local residents and visitors from D.C. and surrounding areas. At this time, though, it’s best to avoid any area of the lake where the water is green or an advisory sign is posted.

Do you have a favorite area of Lake Anna? Where’s your favorite place to go boating if you can’t get to Lake Anna? Let us know in the comments.