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Swimming advisories extended for Lake Anna due to algae bloom

The North Anna and Upper Pamunkey Branches, including Terry’s Run, of Lake Anna in Orange, Louisa and Spotsylvania counties are continuing to experience a harmful algae bloom (HAB). The public is advised to avoid contact with the lake in this area until algae concentrations return to acceptable levels.

The sections of the lake currently under advisory:

Pamunkey Branch (Rt. 719 and Terry’s Run sites added, advisory extended)

  • From the upper inundated waters of the Pamunkey arm of the lake downstream to the 612 Bridge. (Does Include Terry’s Run).

North Anna Branch (Lower North Anna site added, advisory extended)

  • From the upper inundated waters of the North Anna arm of the lake downstream to above the confluence with Pamunkey Branch above Goodwins Point. Does not include “the Splits.”

The samples collected downstream at the confluence of the two branches, at the Lake Anna State Park beach, and at the 208 bridge indicated cyanobacteria densities were at acceptable levels and do not necessitate a swimming advisory. Cyanotoxins were detected at each of these sites, but were at safe swimming levels.

Some harmful algae, called cyanobacteria, can cause skin rash and gastrointestinal illnesses, such as upset stomach, nausea, vomiting and diarrhea. The area to avoid can be seen on an interactive map at A status report containing the updated advisory areas may be viewed at “Lake Anna Status Report (8.12.21).”

To prevent illness, people should:

  • Avoid contact with any area of the lake where water is green or an advisory sign is posted,


  • Not allow children or pets to drink from natural bodies of water.
  • Keep children and pets out of the areas experiencing a harmful algae bloom and quickly wash them off with plenty of fresh, clean water after coming into contact with algae scum or bloom water.
  • Seek medical/veterinarian care if you or your animals experience symptoms after swimming in or near an algal bloom.
  • Properly clean fish by removing skin and discarding all internal organs, and cooking fish to the proper temperature to ensure fish fillets are safe to eat.
  • Contact the Virginia Harmful Algal Bloom Hotline at 1-888-238-6154 if you suspect you experienced health-related effects following exposure to a bloom.
  • Visit to learn more about harmful algae blooms or to report an algae bloom or fish kill.

Samples results provided August 11 from collections on August 5 indicated that at seven locations in the North Anna and Pamunkey Branches, swimming advisories are necessary due to unsafe levels of potential toxin producing cyanobacteria. People and pets are advised to avoid swimming, windsurfing and stand-up-paddle-boarding, as well as other activities that pose a risk of ingesting water. Follow-up monitoring above Route. 208 on the lake is planned (weather permitting) for the second week of September.

Algae blooms can occur when warm water and nutrients combine to make conditions favorable for algae growth. Most algae species are harmless, however, some species may produce irritating compounds or toxins. Avoid discolored water or scums that are green or bluish-green because they are more likely to contain toxins.

The Virginia Department of Health (VDH) and the Virginia Harmful Algal Bloom Task Force, which includes the VDH, the Virginia Department of Environmental Quality, and the Old Dominion University Phytoplankton Laboratory, will continue to monitor water quality in the lake. In general, advisories will be lifted following two consecutive test results with acceptable levels for algal cell counts and/or toxin concentration. An advisory may be lifted or maintained at the discretion of the health department. For example, after one test an advisory may be lifted if results are within safe levels for swimming if other information indicates exposure or human health risk is low.

The Harmful Algal Bloom map is updated to reflect the HAB advisory status of Lake Anna and most recent sample results can be found here “Algal Bloom Surveillance Map.” For more information visit

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