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SCDES Collects Additional Samples, Conducts Third Extensive Survey of Lake Hartwell Harmful Algal Bloom
Certain areas of Lake Hartwell lifted from Recreational Water Watch
FOR IMMEDIATE RELEASE:
June 5, 2025
COLUMBIA, S.C. — The South Carolina Department of Environmental Services (SCDES) continues to monitor the harmful algal bloom (HAB) on Lake Hartwell in order to provide the latest recommendations for protecting public health.
On June 3, SCDES’s Aquatic Science Division (ASD) teams surveyed the lake and collected new water samples from 10 different locations, as identified in the map graphic. SCDES’s Algal Bloom Monitoring M
ap has been updated with sampling locations and observations since June 2.
The bloom is still present in several areas of the lake, however, the ASD field teams noted continued improvement in many coves and nearshore areas compared to the previous survey on May 22. While the bloom appears to be lessening in certain areas, it’s advised to continue to use caution in areas where the bloom is observed.
The June 3 water samples indicate the ongoing presence of cyanobacteria (blue-green algae) capable of producing toxins. The concentration of microcystins was again detected in all 10 samples with a maximum concentration of 0.89 micrograms per liter, which is below the recreational standard of 8 micrograms per liter.
Based on the latest round of lake observations and water sampling, SCDES has updated the Recreational Watch for Lake Hartwell and removed certain areas of the lake, including:
- Tugaloo River lake arm upstream of I-85
- Seneca River lake arm upstream of West Cherry Road
- Six and Twenty lake arm upstream of Centerville Road
The Recreational Watch for Lake Hartwell remains in effect for areas downstream of these road crossings, with the following recommendations:
- avoid direct contact with lake water in areas where the HAB is observed
- keep pets and animals from swimming in or drinking from the lake in areas where the HAB is observed
Please note that the HAB may still be found in areas where the Recreational Watch has been lifted. SCDES encourages caution when recreating in coves or near the shore.
SCDES first issued a Recreational Watch for Lake Hartwell on April 30 after identifying the presence of a HAB. Cyanotoxin concentrations were low or below the analytical detection limit then, as they are in the most recent samples.
The most common symptoms associated with HABs are stomach pain, skin rash, headache, coughing and watery eyes. If a pet displays symptoms after coming into contact with a HAB, please consult with your veterinarian.
SCDES will continue to monitor the Lake Hartwell HAB and communicate with local officials, stakeholders and the public. The agency is also in regular communication with the U.S. Army Corps of Engineers.
As a reminder, HABs are a common occurrence in South Carolina lakes. They are typically observed during the warmer and drier months, and they can persist for several weeks. The blooms can look like bright green spilled paint or blue-green discoloration of the water. With cooler temperatures, heavy winds and rain, blooms may begin to break up and die off.
For more information, contact SCDES’s Bureau of Water at 803-898-8374 or by email at HAB@des.sc.gov. If calling after hours, please leave a message that can be returned. For additional information about harmful algae in South Carolina, visit the SCDES HABs webpage and Algal Bloom Monitoring Map.
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