Harmful Algal Blooms

Harmful Algal Blooms Resource Center

Information and Resources about Harmful Algal Blooms and how they are affecting SML.

Summary of Original Swimming Advisory

On June 6th, the Virginia Department of Health (VDH) issued a Harmful Algal Bloom (HAB) Swimming Advisory for the entire Blackwater arm of Smith Mountain Lake.  VDH advises that swimming on the Blackwater arm could expose people and pets to a potentially harmful algal bloom. Swimming in this area is not recommended until further notice. 

The Virginia Department of Quality (DEQ) collected three samples of lake water on Thursday June 1st in locations of reported algal blooms. These samples were analyzed for concentration of cyanobacteria and potential toxins. VDH reports that unsafe levels of cyanobacteria, aka blue-green algae, are present in samples collected at three locations. 

The VDH reported that while very low concentrations of toxins are present in the samples collected in the Blackwater arm of SML, none of the samples contain toxin levels above regulatory threshold. This does not mean that toxin levels will necessarily remain the same and could perhaps rise.

Regardless of low levels of toxins, VDH advises that you can still experience rashes and allergic reactions to high concentrations of cyanobacteria, so the advice is still to stay out of the water in the Blackwater arm of SML.

Recreational activities such as boating, fishing, and kayaking are all safe, as long as you wash with clean water following. Dogs should be kept out of the Blackwater portion of the lake.  Swimming is fine in the rest of the lake, but keep an eye out for anything that looks like spilled paint, either light green or blue in color. 

When in Doubt, Stay Out.

UPDATE (June 13, 2023)

The Virginia Department of Environmental Quality (DEQ) advised SMLA that they were back the Blackwater arm of SML on June 13th to begin the sampling to determine when the Swimming Advisory can be lifted. VDH guidance states that two sampling events, at least 10 days apart, must show levels of cyanobacteria and toxins below advisory levels before the Swimming Advisory can be lifted.  Six locations, five in the Blackwater and one in Gills Creek will be tested for cyanobacteria levels and toxins in addition to the regularly scheduled sampling DEQ conducts monthly on the lake. A return to the initial three locations that were the basis for the Swimming Advisory may occur if resources allow, according to VDH and DEQ. Results of the June 13th sampling event should be available by the end of the week.

UPDATE (June 15, 2023)

The Smith Mountain Lake Association (SMLA) is aware of potential algae sightings in parts of the Roanoke River including Betty’s Creek, Becky’s Creek and near the SML State Park.  Residents have filed reports with the Virginia Department of Health (VDH).  SMLA is working with Ferrum College to determine whether species of potentially harmful Cyanobacteria are present in samples collected at some of the new reports.  In order to determine if these reports constitute new areas of harmful algal blooms, the Virginia Department of Environment Quality (DEQ) needs to sample and analyze for concentrations of Cyanobacteria and potential toxins. Then VDH will make a determination whether to expand the Swimming Advisory.  VDH did inform us today that they anticipated the SML State Park may deploy signs alerting the public to the presence of Cyanobacteria and that swimmers should be aware of any potential risk. This does not constitute an expansion of the Swimming Advisory.  As soon as we receive test results, we will share more details.

UPDATE (June 16, 2023)

The Smith Mountain Lake Association (SMLA) is in frequent contact with the Virginia Department of Health (VDH) and Virginia Department of Environmental Quality (DEQ).

There is no change to the Harmful Algal Bloom (HAB) Swimming Advisory for the Blackwater arm of Smith Mountain Lake (SML).  We expect results next week from VDH on the samples taken on Tuesday (June 13) by DEQ in the Blackwater arm of Smith Mountain Lake.

At this time, there is not a swimming advisory for the Roanoke River.   We expect DEQ to take samples from those areas reported yesterday by residents next Tuesday (June 20).

Please remember that lake waters are not sterile and there are many ways you continue to recreate and stay safe.  A good practice is to rinse skin exposed to lake water promptly with soap and fresh water.

UPDATE (June 21, 2023)

The HAB Swimming Advisory issued earlier this month by VDH on a portion of Smith Mountain Lake has raised questions and concerns.  Among the questions asked on social media are “what’s being done to remediate the problem, monitor the issue and prevent it from happening again”? Please read the Editorial provided by the Smith Mountain Lake Association.

UPDATE (June 22, 2023)

While SMLA waits for VDH to announce the testing results from last week (June 13), we are happy to share that SMLA has purchased a handheld device we can use to screen samples of lake water for the presence of cyanobacteria. This screening-level type of monitoring is expected to help us, and the community, understand if harmful levels of cyanobacteria (aka blue-green algae) are present.

This tool will not tell us if an area has toxin levels but it will tell us if cyanobacteria are present. We won’t be able to say what kind of cyanobacteria are there, but will know rapidly if they are there in concentrations high enough that a HAB report should be filed with VDH and DEQ.

UPDATE (June 23, 2023)

On June 22, 2023, VDH posted an updated Status Report for the Swimming Advisory on the Blackwater arm of SML. Samples taken on June 13th indicate that unsafe levels of cyanobacteria remain at some sites in the Blackwater. The toxin testing results show that toxin levels are below detection limits and have improved from the first sampling event. Effectively, although cyanobacteria remain at levels considered unsafe in portions of the Blackwater arm, none of these areas are currently toxic.

DETAILS: On June 13th DEQ staff collected water samples at nine (9) locations within the Blackwater arm of SML. Three of these samples were collected at the original sites of the bloom; Kemp Ford Road, Virginia Key and Anthony Ford Boat Ramp. The Anthony Ford Boat Ramp site has improved and now contains safe levels of cyanobacteria and no toxins. The Kemp Ford Road and Virginia Key sites still contain unsafe levels of cyanobacteria but no toxins. Of the remaining six (6) sample sites, two (2) contain unsafe levels of cyanobacteria, but no toxins. The remaining four (4) samples contained cyanobacteria at safe levels and no toxins.

The Swimming Advisory has not been lifted at this time. Even though the Anthony Ford Boat Ramp site has improved, one (1) more sampling event must occur before the advisory can be lifted in this area. The remaining sites where cyanobacteria remain at unsafe levels must be sampled two (2) more times, 10 days apart, both events showing safe levels of cyanobacteria. The VDH anticipates that they will issue a new Status Report during the week of July 10th.
DEQ is scheduled to return to SML on Monday, June 26th to test areas on the Roanoke arm which were reported on the VDH HAB report portal last week.

The SMLA has invited the officials from VDH and DEQ to participate in a public information session, here at the lake, which is tentatively scheduled for Thursday July 6th. Stay tuned for more information on time and location. Meanwhile, the VDH will be preparing an informational webinar responding to the commonly asked questions that we at SMLA are hearing from you on social media and through other communications. The tentative date for this webinar is Wednesday June 28th at 11 am. More details on how to join the webinar will be provided.

While this Swimming Advisory remains in place, this does not mean you cannot enjoy the lake. Proper precautions and following the advisory from VDH regarding swimming should be followed. Recreational activities such as boating, fishing, and kayaking are all safe, if you wash with clean water following. Dogs should be kept out of the Blackwater portion of the lake. Keep an eye out for anything that looks like spilled paint, either light green or blue in color. Do not swim in water that is scummy or smells bad.

UPDATE (July 7, 2023)

Swimming Advisory Lifted for Lower Blackwater Arm

On July 7, 2023, VDH posted an updated Status Report for the Swimming Advisory on the Blackwater arm of SML. Samples taken on June 26th on the lower Blackwater arm of SML contain safe levels of cyanobacteria and toxins. VDH has lifted the Swimming Advisory for the lower portion of the Blackwater arm to just upstream of the confluence with Gills Creek, at Channel Marker B-16.

The Swimming Advisory remains upstream of Gills Creek in the Upper Blackwater arm. DEQ is expected to sample the remaining areas upstream the week of June 10th. Recall that two (2) sampling events, 10 days apart, which show safe levels of cyanobacteria and toxins must occur before modification of the advisory for the Upper Blackwater can occur.

Details: On June 26th DEQ staff collected water samples at four (4) locations within the Blackwater arm. All four sites showed that concentrations of cyanobacteria and toxins are below the advisory levels and are considered safe. Because a prior sampling event on June 13th also showed safe levels, in the Lower Blackwater, the VDH can now modify the Swimming Advisory to only the portions of the Upper Blackwater upstream of Gills Creek, starting at Channel Marker B-16. This means that all of Gills Creek, Bull Run, Little Bull Run, the Lower Blackwater, and coves downstream of Gills Creek are no longer part of the Swimming Advisory.

DEQ staff will sample the remaining sites in the Upper Blackwater arm the week of June 10th. IF and only IF these results show safe levels of cyanobacteria and toxins, then a second sampling event, 10 days following, must also show safe levels before the Swimming Advisory can be lifted for the Upper Blackwater. During the same week of July 10th, DEQ staff also plan to revisit the Roanoke arm, for their regularly scheduled monitoring run, and if time allows, will investigate Roanoke arm citizen reports from the week preceding July 1st. The results of a single sample collected July 6th on the Roanoke arm at the location of a citizen’s report are expected early next week.

While the Swimming Advisory remains in place for the Upper Blackwater arm, this does not mean you cannot enjoy the lake. Proper precautions and following the advisory from VDH regarding swimming should be followed. Recreational activities such as boating, fishing, and kayaking are all safe, if you wash with clean water following. Dogs should be kept out of the Blackwater portion of the lake. Keep an eye out for anything that looks like spilled paint, either light green or blue in color. Do not swim in water that is scummy or smells bad.

UPDATE (July 21, 2023)

Results of all five 7/13/2023 samples had acceptable levels of cyanobacteria. One site (Blackwater River B22) had detectable levels of microcystin, but that concentration was well below the advisory threshold. At the other four sites, all toxins were below detectable levels. In order to lift advisories issued for the Blackwater River arm of Smith Mtn Lake, two consecutive samples with results at acceptable levels collected a minimum of 10 days apart, are necessary. These results are the first set of samples toward lifting the Upper Blackwater River HAB Advisory.

For the Upper Blackwater River, sites originally placed under advisory were shoreline sites. It is customary once a HAB advisory has been established, to replace shoreline sites with representative mid-channel sites. This approach is consistent with how VDH and partners have historically managed response in Lake Anna for the last several years. Lake Anna is ~13,000 acres whereas Smith Mountain Lake is ~30,000 acres in size. Taking mid-channel follow-up samples once a HAB is established in a waterbody, is a reasonable as well as practical method for determining whether or not the general public use is impacted by a HAB event. The public should continue to avoid water with surface scum (which may accumulate near shorelines) and that appears discolored, water that smells, and water that has dead or dying animals such as fish.

Here is a summary of which new channel sites are now representing prior shoreline sites (2), which sites are brand new (2), and which site was resampled (1):

  • “Blackwater River B16” is a new site and represents the river at the current most downstream extent of the advisory (Blackwater River from inundated extent to confluence with Gills Creek).
  • “Blackwater River B22” is a new site that now represents “HAB #311/312 Blackwater River @ Virginia Key Trail B21”.
  • “Blackwater River B28A” is a new site that now represents the former site “4ABWR010.55 Blackwater River at Rock Cliff Road B28”. These are both mid-channel sites. The slight change in location was an to attempt to capture the influence of Standiford Creek, where prior investigations had occurred and scums were observed.
  • “Blackwater River B37” is a brand new site which attempts to capture where prior scums were observed near this bend of the river.
  • “Blackwater River B49” is a resampled site, last sampled on 6/13/2023.

There is one update for the Roanoke River where a site was sampled on 7/6/2023 – there is no advisory on the Roanoke River. This location did not appear to have a visible bloom but a water chemistry value was slightly elevated at the time of DEQ’s site visit. This location can be viewed on the HAB Map as a green dot. Cyanobacteria were detected but were well below advisory thresholds. Toxins were all below detectable limits at this site

UPDATE (August 24, 2023)

Two consecutive samples with cyanobacteria and toxin concentrations at safe levels were collected on July 13 and August 15, allowing VDH to lift the swimming advisory on the Upper Blackwater River.
There is currently no HAB advisory on Smith Mountain Lake. Investigations by boat at five locations (green dots) on the Upper Blackwater River arm of Smith Mountain Lake collected 8/15/23 showed acceptable levels of algae. Toxins were at acceptable levels, and generally below detectable concentrations. Final lab results were received 8/24/23. Swimming, boating and other recreational activities may proceed with standard safe swimming practices throughout the lake. There is no evidence of impacts to drinking water at this time.

Timeline of SML HAB

The timeline of events updated with new information from VDH, DEQ and Ferrum.

Questions and Answers

We know you’ve got more questions. We’ve got some answers. Please read our Q & A.

Town Hall Summary

July 6th Town Hall on the Hazardous Algal Bloom (HAB) situation at Smith Mountain Lake (SML)

Virginia Department of Health

Press Release

On June 6th VDH issued a press release announcing the Swimming Advisory for the Blackwater arm of SML.

On June 7th VDH issued a press release updating the Swimming Advisory for the Blackwater arm of SML.

Swimming advisory

Based on citizen reports of suspected HABs, submitted beginning May 22nd, the DEQ collected samples from three areas in the Blackwater River on June 1st. By June 6th results of the samples indicated that concentrations of cyanobacteria in the samples exceeded the regulatory threshold and VDH implemented the Swimming Advisory for the entire Blackwater arm of SML. The very conservative coverage of such a large area was based upon the results of the sampling for the three sites but also upon a number of other citizen reports that were not sampled June 1st but appeared to be similar in nature to the three initial sampling spots. Toxin levels were reported for the three sites on June 7th and while there were low levels of toxins, none exceeded the regulatory thresholds. View the most up to date Advisory issued by VDH on August 24th.

HAB online report form

VDH requests that citizens report what appear to be conditions on the water surface that may be cyanobacteria blooms. Information required is location, name and contact information, and a photograph. Helpful information includes latitude and longitude which you can get from Google maps. Open Google maps and enter your home address (or address where reporting bloom from), and right click on the map where you see the bloom. The coordinates will pop up in a window which you can put into the report form. This helps DEQ if they need to collect a sample. Reminder, a photograph is critically important as part of your submittal.

HAB Website

The VDH maintains a website that provides significant information to citizens about HABs. 

Virginia Department of Environment Quality

Water quality monitoring stations DEQ regularly monitors. Zoom to search at Smith Mountain Lake, toggle data layers on right to select Water Quality Monitoring Layers. Select individual stations for data.

News Reports


These photos are representative of what has been observed at Smith Mountain Lake since May 22nd this year. All of these photos were taken in the Blackwater arm of the lake. The common description of a HAB is of “spilled paint” however, the light blue coloration is also typical of HABs. Notably, these conditions can change from hour to hour, and from dawn to dusk. Sometimes the surface of the water can often appear to be filmy with an almost oil-like sheen. Often when the blooms turn blue, they also have an organic odor similar to rotting grass clippings. And when the bloom seems to disappear it may still be present, suspended in the water column, as clumped colonies of cyanobacteria. These clumps can be visible as green dots.

What can Residents do to Protect the Water of SML?


Smith Mountain Lake residents are encouraged to contact their Virginia State legislators about the health of SML.  Share your thoughts, experiences and concerns.

Buffer Gardens.  

Buffer gardens are the single most effective solution for lake-front residents interested in protecting the water of Smith Mountain Lake.  Buffer landscaping consists of vegetation planted near the lakeshore to trap sediments and to filter nutrients and pollutants.  A green lawn without a buffer garden leads to a green lake.

Septic Management. 

Proper septic system maintenance and periodic septic tank pumping is critical to avoid raw sewage from seeping into the lake.  Have you had your septic system inspected recently?

Save our Streams. 

The condition of the streams that flow into Smith Mountain Lake are a leading indicator about the health of the lake.  The Smith Mountain Lake Association combines forces with two other organizations – the Virginia Save Our Streams Program and the Blue Ridge Foothills and Lakes Chapter of the Virginia Master Naturalist Program – to conduct semi-annual stream monitoring at 16 locations around the lake.

Vessel Pump Out Program.

Smith Mountain Lake is a designated no discharge zone.  It is illegal to release any wastewater into the lake. Boats docked at 19 marinas on SML are eligible for free pump out services from May 20th to September 10th.  Don’t poo in the blue.

Pet Waste.

When your dogs poop on their daily walks, we pick it up, right? Those little baggies go into the trash, when you get home. What about when you let those puppies out into the yard? Someone might pick up those fun little presents, but where do you dispose of them? Do you chuck them into the woods or put them into the trash? Believe it or not, pet waste contains nutrients such as phosphorus and nitrates which can be washed directly into the lake when it rains. Prevent nutrients from entering the lake by tossing pet waste into the trash.

Goose Control.

Did you know that one pound of goose poop contains enough phosphorus to lead to the growth of 1,200 pounds of algal bloom? It may seem impossible to keep geese off your yard, but there is one good way to do it, and that is by planting a buffer garden. Geese will not climb up riprap and come onto a lawn with a barrier of grass or other dense plantings at least 12 inches high. These plantations are a simple barrier to goose invasion as well as a good filter for nutrients coming off your lawn.

Join SMLA.

The Smith Mountain Lake Association is a nonprofit 501(c)(3) that relies on memberships and grants to fund the programs that keep Smith Mountain Lake clean and safe.  With over 11,000 individual lake front property owners and hundreds of local businesses supported by the lake area economy, SMLA could enhance, increase and expand its efforts to protect Smith Mountain Lake if it had more than its current 1,000 individual, family and business partner members.  Be a Steward of the Lake and join us!


Are you already a member?  Do you vacation at Smith Mountain Lake?  Would you like to ensure the lake is enjoyed be generations that follow.  Please donate to the Smith Mountain Lake Association.  It’s tax deductible.

More Information

Water Quality Monitoring Program.

The Smith Mountain Lake Association and Ferrum College have been monitoring the water quality of SML for over 37 years.  Each summer, Ferrum College faculty and students, along with SMLA volunteers, monitor the lake water for nutrients, bacteria, and algal blooms.  

Check out the New Ferrum College Water Quality Boat. 

Thanks to a generous grant provided by Appalachian Power and the AEP Foundation, the SML Water Monitoring Program was able to purchase a new pontoon boat.  

SMLA HAB Working Group.

A direct result of the HAB Swimming Advisory, declared by Virginia Department of Health on June 6th, the first of its kind on Smith Mountain Lake, the SMLA has become aware that there is a limited channel of communication to residents, business owners, and others. In order to improve local communication, we are going to implement a SMLA HAB Working Group, comprised of a diverse group of SML stakeholders. The initial goal of the Working Group will be to develop a community communication strategy to spread information about potential HAB situations and to bring needed updates to the community. Secondary to that first goal will be to develop a resiliency strategy which could include initiatives such as local monitoring and sampling efforts to enhance the work done by state agencies and Ferrum College.