Navarro River: toxic algae advisories
Navarro River, Mendocino County. See all Mendocino County waters.
What the state's records say
Danger advisory, last posted Aug 27, 2026. No all-clear recorded.
6 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: Toxins may be at levels that can seriously harm people and animals. Stay out of the water and keep children and pets away from the water and the shore.
Before you go, check the state's official algae page and any signs posted at the water.
Dogs at Navarro River
The state has an advisory on file for Navarro River (Danger advisory), last posted Aug 27, 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 |
|---|---|
| Hendy Woods State Park | Algal mat alert sign, last posted Aug 27, 2026. No all-clear recorded. |
| Bridge by Hendy Woods | Algal mat alert sign, last posted Jul 27, 2026. No all-clear recorded. |
| Philo California | The state's latest record, from Nov 26, 2024, recommends no advisory. |
| Hendy Woods | Algal mat general awareness sign, last posted Dec 13, 2023. No all-clear recorded. |
| below Highway-1 Bridge | Algal mat general awareness sign, last posted Jul 14, 2021. No all-clear recorded. |
| Navarro River | Algal mat general awareness sign, last posted Jul 14, 2021. No all-clear recorded. |
| at Greenwood Road | The state's latest record, from Jul 8, 2021, recommends no advisory. |
| Navarro River lagoon | Danger advisory, last posted Sep 24, 2020. No all-clear recorded. |
Advisory history
Every advisory record the state has published for Navarro 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 27, 2026 | Hendy Woods State Park | Algal mat alert sign | Alert-detached mats observed; Bottom/benthic bloom observed |
| Aug 13, 2026 | Hendy Woods State Park | Algal mat alert sign | Alert-detached mats observed; Bottom/benthic bloom observed |
| Jul 30, 2026 | Hendy Woods State Park | Algal mat alert sign | Alert-detached mats observed; Bottom/benthic bloom observed |
| Jul 27, 2026 | Bridge by Hendy Woods | Algal mat alert sign | Bottom/benthic bloom observed; Suspected illness reported; Under investigation; Visual monitoring only-present bloom |
| Jul 16, 2026 | Hendy Woods State Park | Algal mat alert sign | Alert-detached mats observed; Bottom/benthic bloom observed |
| Jul 16, 2026 | Hendy Woods State Park | Algal mat alert sign | Alert-detached mats observed; Bottom/benthic bloom observed |
| Jul 16, 2026 | Hendy Woods State Park | Algal mat alert sign | Alert-detached mats observed; Bottom/benthic bloom observed |
| Aug 25, 2025 | Hendy Woods State Park | Algal mat alert sign | Advisory based on visual and toxins; Alert-detached mats observed; Bottom/benthic bloom observed |
| Aug 13, 2025 | Hendy Woods State Park | Algal mat alert sign | Alert-detached mats observed; Bottom/benthic bloom observed; Visual monitoring only-present bloom |
| Aug 13, 2025 | Hendy Woods State Park | Algal mat alert sign | Alert-detached mats observed; Bottom/benthic bloom observed; Visual monitoring only-present bloom |
| Aug 13, 2025 | Hendy Woods State Park | Algal mat alert sign | Alert-detached mats observed; Bottom/benthic bloom observed; Visual monitoring only-present bloom |
| Nov 26, 2024 | Philo California | None | De-posting advisory. |
| Aug 22, 2024 | Philo California | Algal mat alert sign | Advisory based on visual and toxins; Bottom/benthic bloom observed |
| Aug 20, 2024 | Philo California | Algal mat general awareness sign | Testing results below posting triggers |
| Dec 13, 2023 | Hendy Woods | Algal mat general awareness sign | No cyano bloom w/photos; Visual monitoring only-absent bloom |
| Sep 8, 2023 | Hendy Woods | Algal mat alert sign | Alert-detached mats observed; Bottom/benthic bloom observed; visual monitoring based advisory |
| Aug 14, 2023 | Hendy Woods | Algal mat alert sign | Alert-detached mats observed; Bottom/benthic bloom observed; visual monitoring based advisory |
| Jul 14, 2021 | below Highway-1 Bridge | Algal mat general awareness sign | |
| Jul 14, 2021 | Navarro River | Algal mat general awareness sign | |
| Jul 8, 2021 | at Greenwood Road | None | Testing results below posting triggers |
| Sep 24, 2020 | Navarro River lagoon | Danger | Advisory based on visual and toxins |
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.