Division of Water Quality
Matt Warner Reservoir Recreational Monitoring
Matt Warner Reservoir is located on Diamond Mountain, north of Vernal in Uintah County. 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 19, 2026: Harmful algal bloom (HAB) monitoring update
BE CAREFUL: A harmful algal bloom is present at Matt Warner 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