Gunlock Reservoir Algal Bloom Monitoring 2018

Report a Bloom

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

Call Utah Poison Control Center

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


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Help us track cyanobacteria blooms with your smartphone. Go to cyanos.org for more info.


Gunlock Reservoir is located 15 miles northwest of St. George. The reservoir was originally constructed for irrigation and flood control, but it is also a popular boating, water sports, and fishing destination.

Update August 14, 2018

The Division of Water Quality (DWQ) visited Gunlock Reservoir on August 8, 2019. The monitoring crew noticed a small bloom along the shore near the boat launch on the southeast end of the reservoir. The crew collected surface samples at this location. Toxin strip results were non-detect for both anatoxin-a and microcystin.