Tuolumne River: toxic algae advisories
Tuolumne River, Tuolumne County. See all Tuolumne County waters.
What the state's records say
Caution advisory, last posted Aug 21, 2026. No all-clear recorded.
4 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 Tuolumne River
The state has an advisory on file for Tuolumne River (Caution advisory), last posted Aug 21, 2026, 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 |
|---|---|
| NF ~0.6mi below Basin Cr. (536TMR003) | Algal mat alert sign, last posted Aug 21, 2026. No all-clear recorded. |
| Highway 120 Bridge | Algal mat alert sign, last posted Nov 4, 2022. No all-clear recorded. |
| Pate valley | Algal mat alert sign, last posted Nov 4, 2022. No all-clear recorded. |
| (Middle Fk) 108 | Caution advisory, last posted Oct 7, 2021. No all-clear recorded. |
| Tuolumne River | The state's latest record, from Feb 21, 2019, recommends no advisory. |
Advisory history
Every advisory record the state has published for Tuolumne River, 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 |
|---|---|---|---|
| Aug 21, 2026 | NF ~0.6mi below Basin Cr. (536TMR003) | Algal mat alert sign | Alert-high concentration toxins |
| Aug 21, 2026 | NF ~0.6mi below Basin Cr. (536TMR003) | Algal mat alert sign | Alert-high concentration toxins |
| Nov 4, 2022 | Highway 120 Bridge | Algal mat alert sign | Bottom/benthic bloom observed |
| Nov 4, 2022 | Pate valley | Algal mat alert sign | Bottom/benthic bloom observed |
| Sep 27, 2022 | Pate valley | Algal mat alert sign | Bottom/benthic bloom observed |
| Oct 7, 2021 | (Middle Fk) 108 | Caution | Advisory based on visual and toxins |
| Feb 21, 2019 | Tuolumne River | None |
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.