Ewing Reservoir: toxic algae advisories
Ewing Reservoir, Trinity County. See all Trinity County waters.
What the state's records say
Caution advisory, last posted Nov 12, 2025. No all-clear recorded.
2 reported spots here have an advisory with no all-clear recorded.
Reporting is voluntary, so the state may not have recorded an end even if conditions changed. Check posted signs and the official map.
What this level asks: Algae that can make toxins may be present. Keep people, children and pets away from algae and scum, and do not let pets drink the water.
Before you go, check the state's official algae page and any signs posted at the water.
Dogs at Ewing Reservoir
The state has an advisory on file for Ewing Reservoir (Caution advisory), last posted Nov 12, 2025, and no all-clear recorded. Keep your dog out of the water and away from scum on the shore until the state records an end.
Reported spots
The state records each report at a spot, such as a beach or a boat ramp. Each spot's latest deciding record:
| Spot | Status |
|---|---|
| Lakewide | Caution advisory, last posted Nov 12, 2025. No all-clear recorded. |
| Spot not described | Caution advisory, last posted Jul 15, 2021. No all-clear recorded. |
Advisory history
Every advisory record the state has published for Ewing Reservoir, newest first. "None" is the state's record that no advisory was recommended on that date. "NA" records do not change a status.
| Date | Spot | State's level | Notes |
|---|---|---|---|
| Nov 12, 2025 | Lakewide | Caution | Advisory based on visual and toxins; Floating/planktonic bloom observed; Lake-wide advisory |
| Nov 3, 2025 | Lakewide | Caution | Floating/planktonic bloom observed; Lake-wide advisory; visual monitoring based advisory |
| Apr 10, 2025 | Lakewide | Caution | Floating/planktonic bloom observed; Lake-wide advisory; visual monitoring based advisory |
| Apr 7, 2025 | Lakewide | Caution | Floating/planktonic bloom observed; Lake-wide advisory; Suspected bloom, investigation ongoing; Under investigation |
| Nov 18, 2024 | Lakewide | Caution | Floating/planktonic bloom observed; Lake-wide advisory; Suspected bloom, investigation ongoing; Under investigation |
| Nov 18, 2024 | Lakewide | Caution | Floating/planktonic bloom observed; Lake-wide advisory; Suspected bloom, investigation ongoing; Under investigation |
| Nov 18, 2024 | Lakewide | Caution | Floating/planktonic bloom observed; Lake-wide advisory; Suspected bloom, investigation ongoing; Under investigation |
| Dec 29, 2023 | Lakewide | Warning | Advisory based on visual and toxins; Alert-scum observed; Under investigation |
| Dec 20, 2023 | Lakewide | Caution | Under investigation; visual monitoring based advisory |
| Dec 13, 2023 | Lakewide | Caution | Under investigation; visual monitoring based advisory |
| Jul 15, 2021 | Spot not described | Caution | Lake-wide advisory |
Source
Advisory data: California State Water Resources Control Board, Freshwater Harmful Algal Bloom Program, via data.ca.gov (public domain). Advisories are recommendations; reporting is voluntary and incomplete. The state's data. An advisory ends only when the state records a later "None" (no advisory recommended) at the same spot, or an end date. A blank end date is unknown.