Virgin River Watershed Recreational Monitoring 2021

This webpage is updated monthly with information provided by Zion National Park (ZNP). The Utah Division of Water Quality does not routinely conduct HAB sampling within the Virgin River Watershed. If you have additional questions, please contact ZNP by calling (435) 772-3256.

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Toxins Not Detected In Latest Sample
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Sample Results Pending
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Toxic Algal Bloom Found, Toxin Results Pending, or Toxins Below Advisory Thresholds
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Toxins Above Advisory Thresholds

Report a Bloom

24-Hour DEQ Environment Incidents Line: (801) 536-4123

Call Utah Poison Control Center

Poison Control (800) 222-1222

If you believe you or your pet have been exposed to a harmful algal bloom, call (800) 222-1222.

Update November 17, 2021

Zion NP continues to monitor monthly for the presence of harmful cyanobacteria and cyanotoxins. Zion NP staff take a “multiple lines of evidence” approach when using data to issue recreational advisories. Monitoring efforts in the North Fork of the Virgin River have shown consistent non-detects for toxins. Further, no toxigenic cyanobacteria have been present in visual surveys in the North Fork of the Virgin River for two consecutive months. Therefore, Zion NP is rescinding the existing Health Watch advisory for the North Fork of the Virgin River. Please remain vigilant for cyanobacteria when recreating in the North Fork of the Virgin River and upstream connected tributaries. In North Creek, a toxin sample has recently been collected above the Danger Advisory threshold. Therefore, Zion NP is elevating the advisory on North Creek and connected upstream tributaries to a Danger Advisory where recreators should avoid all contact with the water. Permits may still be issued during a Danger Advisory. La Verkin Creek will remain a Health Watch. During a Health Watch, recreators should avoid primary contact recreation. Do not drink instream water anywhere in the park at this time. Hike in or filter water directly from a spring source.


Update September 28, 2021

The North Fork of the Virgin River and North Creek, tributaries to the Virgin River, have downgraded their advisory to a Health Watch. Toxin levels have been low to non-detect in the North Fork of the Virgin River and North Creek in August and September samples, however, the toxin-producing cyanobacteria is still present. La Verkin Creek remains at a Health Watch.

  • During a Health Watch, do not submerge your head in the water. Toxins can enter the body by swallowing water or through the nose, eyes, or open wounds.
  • Do not drink river water. Toxins cannot be filtered out by standard hiking filtration methods.
  • Dogs must be kept on a leash. If pets get into the river, remove them from the water immediately, rinse off their fur thoroughly, and monitor for symptoms of toxin poisoning. A dog can die in as little as 15 minutes from anatoxin-a poisoning.

Please toggle the buttons below for more information on the current risk of harmful algal bloom exposure in Zion National Park.


Update August 23, 2021

The Warning Advisory for the North Fork Virgin River remains in place. Toxin levels within the North Fork Virgin River are decreasing but still remain present in harmful algal bloom mats within the water.

North Creek remains in the Warning Advisory category and La Verkin creek remains at a Health Watch.

  • During a Warning Advisory and Health Watch, do not submerge your head in the water. Toxins can enter the body by swallowing water or through the nose, eyes, or open wounds.
  • Do not drink river water. Toxins cannot be filtered out by standard hiking filtration methods.
  • Dogs must be kept on a leash. If pets get into the river, remove them from the water immediately, rinse off their fur thoroughly, and monitor for symptoms of toxin poisoning. A dog can die in as little as 15 minutes from anatoxin-a poisoning.
  • Permitted waterbody activities, such as permitted canyoneering, are allowed.

Please toggle the buttons below for more information on the current risk of harmful algal bloom exposure in Zion National Park.


Update June 1, 2021

The Danger Advisory for the North Fork Virgin River has been downgraded to a Warning Advisory based on May 2021 sampling results. During a Warning Advisory, visitors are advised to avoid submerging their heads in the water.

This determination was made by Zion National Park due to the absence of anatoxin-a in samples collected in the North Fork of the Virgin River, following the Utah Harmful Algal Bloom (HAB) Recreational Advisory Guidance and the Park’s Interim HAB Advisory Decision Criteria.

North Creek remains in the Warning Advisory category and La Verkin creek remains at a Health Watch.

Please click the links below for more information on the current risk of harmful algal bloom exposure in Zion National Park.


Update March 24, 2021

The Warning Advisory for the North Fork Virgin River has been upgraded to a Danger Advisory.

Due to the high toxin concentration detected at the Temple of Sinawava site following the Utah Harmful Algal Bloom (HAB) Recreational Advisory Guidance and the Park’s Interim HAB Advisory Decision Criteria, the Zion National Park has elevated the advisory on the North Fork of the Virgin River to a “Danger” Advisory. During a Danger Advisory, visitors are advised to avoid all contact with the water until further notice.

North Creek remains in the Warning category. La Verkin Creek remains at a Health Watch.

Please toggle the buttons below for more information on the current risk of harmful algal bloom exposure in Zion National Park.

What risk does cyanobacteria found in harmful algal blooms pose to recreators in Zion National Park?

  • Cyanobacteria may produce dangerous liver and nervous system toxins; toxin concentrations can reach levels that affect the health of people, pets, and livestock.
  • Children are especially vulnerable to cyanotoxins.
  • 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.
  • Symptoms include skin rash, salivation, drowsiness, tingling, burning, numbness, pain, incoherent speech, muscle contractions or twitching, vomiting, and diarrhea.

What is the current situation?

Since July 2020, the National Park Service (NPS) in Zion National Park has been routinely collecting both cyanotoxin and toxigenic cell count densities from harmful algal blooms on a monthly basis in several water bodies inside park boundaries. During this time, NPS, the Division of Water Quality (DWQ), and the Utah Department of Health (UDOH) have developed interim data-driven decision guidance for waterbody advisories during harmful algal blooms in Zion National Park.

Following this new guidance criteria, for the month of November, although cyanotoxins were still present, concentrations were below the Danger Advisory thresholds in the North Fork Virgin River, and North Creek waterbodies and were below Warning Advisory thresholds in LaVerkin Creek.

What do lower cyanotoxin concentrations mean for recreation in Zion National Park?

With lower cyanotoxin concentrations, The North Fork Virgin River, and North Creek Danger Advisories will be downgraded to a Warning Advisory and LaVerkin Creek will be downgraded to a Health Watch.

  • During a Warning Advisory and Health Watch, do not submerge your head in the water. Toxins can enter the body by swallowing water or through the nose, eyes, or open wounds.
  • Do not drink river water. Toxins cannot be filtered out by standard hiking filtration methods.
  • Dogs must be kept on a leash. If pets get into the river, remove them from the water immediately, rinse off their fur thoroughly, and monitor for symptoms of toxin poisoning. A dog can die in as little as 15 minutes from anatoxin-a poisoning.
  • Permitted waterbody activities, such as permitted canyoneering, are allowed.

What action is taken outside of the Park?

In other areas of the North Fork of the Virgin River, outside of Zion National Park borders, the Southwest Utah Public Health Department has issued a public health warning. Signs have been posted by individual cities and towns to advise recreators of the risks associated with exposure. Residents should adhere to these guidelines:

  • Do not swim in the signed area
  • Avoid areas of algae scum
  • Do not let animals play in the river, drink from the river, or eat algal scum
  • Do not ingest the water
  • Clean fish well and discard guts

This warning does not apply to Quail Creek Reservoir, Sand Hollow Reservoir, or the Santa Clara River basin.

Is drinking water safe?

The Utah Division of Drinking Water is working with local utilities to ensure drinking water that originates from the river is free of cyanotoxins. Currently, the Washington County Water Conservancy District, Zion National Park, and the Towns of Virgin and Rockville are not using the North Fork of the Virgin River as a drinking water source. Continued daily tests of Springdale drinking water and agricultural water have not detected the presence of cyanotoxins. The Town of Springdale will continue testing drinking water to make sure the water is safe.

How does cyanobacteria affect agricultural water use?

The Utah Department of Agriculture and Food suggests that livestock producers provide a different drinking water source for livestock and restrict livestock access to the North Fork of Virgin River where possible. There is limited information on plant uptake of cyanotoxins. The main concern is protecting irrigators from these cyanotoxins. Practice good hygiene, especially those areas that come in contact with irrigation water.

How do you determine exposure risk?

The NPS, DWQ, and UDOH have worked to characterize exposure risk of benthic cyanobacteria in the Virgin River in order to better compare toxin results to the current DWQ/DOH HAB Guidance and recreational thresholds.

Benthic cyanobacteria attach themselves to the bottom of rivers and lakes and can appear as mats on rocks, submerged debris, sand, cobbles, or plants attached to the bottom of a waterbody.The water can appear clear where these mats are growing. Recreational thresholds are set at 15 μg/L (micrograms per liter) of anatoxin-a for a Warning Advisory and 90 μg/L of anatoxin-a for a Danger Advisory.

Cyanotoxin levels detected in the cyanobacterial growth and within the water column after the mats are disturbed have been much greater than the DWQ/DOH recommended danger advisory threshold for cyanotoxins dissolved in water. More specifically:

  • In the summer of 2020, very high anatoxin-a levels were found within the benthic cyanobacteria mats themselves. Toxins within the mats, in all samples, were greater than 550μg/L of anatoxin-a.
  • All water column samples taken without disturbing the cyanobacterial mats have been free of anatoxin-a.
  • In July, a sampling design called ‘integrated disturbance’ began within the park. This involves collecting water column samples after a water quality scientist walked along a benthic cyanobacteria mat, imitating typical recreation in the river. All of the integrated disturbance water column sample results came back with anatoxin-a concentrations greater than 550 μg/L.