Calder Reservoir is located on Diamond Mountain, north of Vernal in Uintah County. DEQ’s recreational water quality monitoring checks for Harmful Algal Blooms (HABs). Find the most recent Newton Reservoir monitoring information below.
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Updates:
December 1, 2025: Recreational water quality monitoring update
Recreational water quality monitoring has ended for the season. Monitoring will resume in June or July 2026. Harmful algal blooms can occur year-round, so know what to look for and always check before recreating.
October 10, 2025: Harmful algal bloom (HAB) monitoring update
BE CAREFUL: A harmful algal bloom is present at Calder Reservoir. Algae in the water may be producing dangerous toxins that can make humans and animals sick.
TriCounty Health Department has issued a WARNING ADVISORY.
If you visit Calder Reservoir:
- Do not swim or water ski
- Avoid areas of algae when boating
- Clean fish well and discard guts
- Keep animals away
- Don’t drink the water
- Know how to recognize a harmful algal bloom
July 23, 2025: Harmful algal bloom (HAB) monitoring update
BE CAREFUL: A harmful algal bloom is present at Calder Reservoir. Algae in the water may be producing dangerous toxins that can make humans and animals sick.
TriCounty Health Department has issued a WARNING ADVISORY.
If you visit Calder Reservoir:
- Do not swim or water ski
- Avoid areas of algae when boating
- Clean fish well and discard guts
- Keep animals away
- Don’t drink the water
- Know how to recognize a harmful algal bloom