This webpage is updated monthly with information provided by Zion National Park. The Utah Division of Water Quality does not routinely conduct HAB sampling within the Virgin River Watershed. If you have additional questions, please contact Zion National Park by calling (435) 772-3256.
This webpage is updated with information provided by Zion National Park.
Updates
Babylon Road Area:
Check for mats
May 14, 2026: Harmful algae mats monitoring update
Warning: Local officials have confirmed the presence of harmful algae mats at the Babylon Road area.
We recommend:
Harmful algae mats are present. Touching or eating mats can make humans sick and may be deadly for dogs.
- Do not filter drinking water here
- Do not touch or eat algae mats
- Keep dogs and young children away
- Wading, fishing and paddling are OK
Select the “Learn More” tab at the top of this page for information on how to enjoy the water safely.
Confluence Park:
Check for mats
May 13, 2026: Harmful algae mats monitoring update
Warning: Multiple lines of evidence suggest that a dog died this week after consuming algae mats at this location. Although field inspections have not occurred, Harmful algae mats are likely present. Touching or eating mats can make humans sick and may be deadly for dogs.
- Do not touch or eat any algae mats
- Keep children away from any algae mats
- Keep animals away from any algae mats
- Wading, fishing, and paddling are OK
- Know how to recognize a harmful algae mats
Since July 2020, the National Park Service (NPS) in Zion National Park has been monitoring harmful algal bloom (HAB) toxin production on a monthly basis at several water bodies inside the park.
Cyanobacteria and HABs in the Virgin River are different from what is commonly seen in Utah’s lakes and reservoirs. This cyanobacteria grows in mats on the bottom of the riverbed, often attached to rocks or plants. It may be brown, black, tan, or green and comes in a variety of textures.
How can I stay safe while recreating in Zion National Park?
Why are habs in zion national park dangerous?
Cyanobacteria living in the Virgin River (including “The Narrows” and other locations in Zion Canyon) may produce dangerous toxins. These toxins target the liver and nervous system and are dangerous for people and animals.
Toxins can be absorbed through eyes, nose, or mouth by swimming in contaminated water – very small or even invisible pieces of the cyanobacterial growth may contain enough toxin to cause harm.
What are the symptoms of HAB exposure?
Symptoms of toxin exposure include:
If you think you have been exposed, immediately contact the Utah Poison Control Center at (800) 222-1222.
How does Zion National Park determine exposure risk?
The NPS, DWQ, and Utah Department of Health and Human Services have worked to characterize exposure risk from HABs in the Virgin River in order to better compare toxin results to the current DWQ/DHHS HAB Guidance and Recreational Thresholds.
Zion National Park staff rely on three lines of evidence for issuing recreational advisories:
- The presence or absence of known toxin-producing cyanobacteria species.
- The presence or absence of toxins in the water body using SPATT bags.
- ‘Benthic disturbance sampling’ – a process where a water quality scientist walks along a cyanobacterial mat (imitating recreation) and then measures the concentration of toxins produced.