Division of Water Quality
Gunlock Reservoir Recreational Monitoring
Gunlock Reservoir is located approximately 15 miles northwest of St. George. DEQ’s recreational water quality monitoring checks for two health concerns: Harmful Algal Blooms (HABs) and Waterborne Pathogens (E. coli). Find the most recent monitoring information below.
Warning Advisory
Harmful Algae Present
- 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
Updates
August 17, 2026: Harmful algal bloom (HAB) monitoring update
BE CAREFUL: A harmful algal bloom is present at Gunlock Reservoir. Algae in the water may be producing dangerous toxins that can make humans and animals sick.
If you visit the area:
- Do not swim or water ski
- Avoid areas of algae when boating
- Clean fish well and discard skin and guts
- Keep animals away
- Don't drink the water
- Know how to recognize a harmful algal bloom
June 26, 2026: Harmful algal bloom (HAB) monitoring update
BE CAREFUL: Our monitoring team saw visible signs of a harmful algal bloom at Gunlock 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:
- Do not swim or water ski in areas of algae
- Avoid areas of algae when boating
- Clean fish well and discard skin and guts
- Keep animals away
- Don't drink the water
- Know how to recognize a harmful algal bloom
May 13, 2025: Harmful algal bloom (HAB) monitoring update
BE CAREFUL: Local officials have observed visible signs of a harmful algal bloom at Gunlock 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:
- Do not swim or water ski in areas of algae
- Avoid areas of algae when boating
- Clean fish well and discard skin and guts
- Keep animals away
- Don’t drink the water
- Know how to recognize a harmful algal bloom