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​Harmful Algal Blooms

Algae occur naturally in all waterbodies and are a vital part of the ecosystem. When favorable conditions occur in a water body (e.g. excess nutrients, sunny conditions, warm temperatures and/or low-flow), many algae species may grow excessively, producing a nuisance bloom. A harmful algal bloom, or HAB, occurs when toxin-producing cyanobacteria, also known as blue-green algae, grow excessively in a body of water. These bacteria can produce toxins which may affect the liver, nervous system and/or skin in animals or humans. Not all cyanobacteria produce toxins and some produce toxins only under certain conditions.

HABs can have a variety of different colors and looks. HABs may appear bright green, blue-green, brown, red and/or white in color. Some HABs may look like spilled paint, pea soup, parallel streaks and/or green dots or globs in the water. They often have a grainy, sawdust-like appearance upon closer inspection.

Brown algal bloomBlue green algal bloomGreen algal bloom

Report a Bloom:

If you suspect that you have seen a HAB, please report the bloom to the Division of Water by calling 502-564-3410 or emailing Report A Bloom​. After hours and on weekends, you may contact the 24-hour hotline at 502-564-2380 or 1-800-928-2380. Blooms can also be reported using the bloomWatch app.​

For information about bloomWatch or to download the app, please follow the links below.


To get started using bloomWatch please view the Quick Start Guide.

Recommended Precautions:

The following guidelines are recommended to avoid exposure to HABs:
  • Individuals should avoid direct contact with affected water that has unusual color or where blue-green algae have been identified, including swimming, wading, paddling, diving, and water skiing.
  • People who are prone to respiratory allergies or asthma should avoid areas with HABs. Children may be particularly sensitive.
  • If you come into contact with water containing blue-green algae, wash off with clean, fresh water. In some cases, skin irritation will appear after prolonged exposure. If symptoms persist, consult your local health care provider.
  • Fish fillets (not organs) may be consumed after the fillets have been rinsed in clean, non-lake water.
  • Prevent pets and livestock from coming into contact with water where HABs are apparent.

If you are concerned that you have symptoms that are a result of exposure to HABs please see your doctor and call your local health department.

Additional Information:

HABs can develop over a short period of time. Visitors are still advised to be aware of the potential for a harmful algal bloom and follow the recommended precautions.

To read more about HABs, click on the links below:

​To see current advisories, please access the Division of Water Harmful Algal Bloom (HAB) Viewer 

(Note:  this viewer will only work when using one of these web browsers: Google Chrome, Firefox or Safari.) Public lakes or rivers identified with a HAB advisory remain open to the public.