Mantua Reservoir Recreational Monitoring

Warning Advisory

Harmful Algae Present

Do not swim icon. Boat caution icon. Fishing is ok icon, although the pictured fishhook optimistically contains no bait.
  • Do not swim or water ski
  • Avoid areas of algae when boating
  • Keep animals away
  • Do not drink the water
  • Clean fish well and discard guts
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Do not swim icon. Boat caution icon. Fishing is ok icon, although the pictured fishhook optimistically contains no bait.
Learn More About
Harmful Algal Blooms
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Icon of an ancient, prior-century phone.

Report a Bloom • (801) 536-4123

Utah Poison Control • (800) 222-1222

Updates:

September 14, 2023: Harmful algal bloom (HAB) monitoring update

BE CAREFUL: A harmful algal bloom is present at Mantua Reservoir. Algae in the water is producing dangerous toxins that can make humans and animals sick. 

Bear River Health Department has issued a WARNING ADVISORY. 

If you visit Mantua Reservoir:

August 31, 2023: Harmful algal bloom (HAB) monitoring update

BE CAREFUL: A harmful algal bloom is present at Mantua Reservoir. Algae in the water is producing dangerous toxins that can make humans and animals sick. 

Bear River Health Department has issued a WARNING ADVISORY. 

If you visit Mantua Reservoir:

August 17, 2023: Harmful algal bloom (HAB) monitoring update

BE CAREFUL: A harmful algal bloom is present at Mantua Reservoir. Algae in the water is producing dangerous toxins that can make humans and animals sick. 

Bear River Health Department has issued a WARNING ADVISORY. 

If you visit Mantua Reservoir:

August 8, 2023: Harmful algal bloom (HAB) monitoring update

BE CAREFUL: A harmful algal bloom was spotted at Mantua Reservoir Algae on 8/7 in the water and may be producing dangerous toxins that can make humans and animals sick. 

Bear River Health Department has issued a WARNING ADVISORY. 

If you visit the Mantua Reservoir:

July 13, 2023: Harmful algal bloom (HAB) monitoring update

GOOD NEWS: Samples taken the last two weeks at Mantua Reservoir have come back below Department of Health advisory thresholds. Low levels of harmful algae are still present, so know how to recognize a harmful algal bloom and avoid areas of visible algae while recreating.

July 11, 2023: Harmful algal bloom (HAB) monitoring update

BE CAREFUL: Low levels of harmful algae are still present in areas of Mantua Reservoir as of July 10th. Recreators to the reservoir should avoid contact with areas where algae is visible.

We recommend:

June 30, 2023: Harmful algal bloom (HAB) monitoring update

BE CAREFUL: Harmful algae and toxins were present in the sample collected at Mantua Reservoir on 6/26. Harmful algae may be present in some areas of the reservoir. We will continue to monitor and post updates here next week.

If you visit the reservoir, we recommend:

June 26, 2023: Harmful algal bloom (HAB) monitoring update

BE CAREFUL: Our monitoring team saw visible signs of a harmful algal bloom at Mantua Reservoir. There could be algae in the water producing dangerous toxins. We collected samples and results are pending. Check back here for updates.

In the meantime we recommend: