Napa-Sonoma Marshes Wildlife Area: toxic algae advisories
Napa-Sonoma Marshes Wildlife Area, Napa County. See all Napa County waters.
What the state's records say
Danger advisory, last posted Oct 8, 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: 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 Napa-Sonoma Marshes Wildlife Area
The state has an advisory on file for Napa-Sonoma Marshes Wildlife Area (Danger advisory), last posted Oct 8, 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 |
|---|---|
| pond 8 | The state's latest record, from Jun 10, 2026, recommends no advisory. |
| Huichica (HCU) Pond 8 near entrance on Milton Rd | Danger advisory, last posted Oct 8, 2025. No all-clear recorded. |
| Huichica Creek Wildlife Area near entrance on Buchli Station Rd | Danger advisory, last posted Oct 8, 2025. No all-clear recorded. |
Advisory history
Every advisory record the state has published for Napa-Sonoma Marshes Wildlife Area, 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 |
|---|---|---|---|
| Jun 10, 2026 | pond 8 | None | Updates from routine monitoring program-organization |
| Jun 3, 2026 | pond 8 | None | Updates from routine monitoring program-organization |
| Jun 3, 2026 | pond 8 | Visual observation | Visual monitoring only-present bloom |
| Jun 3, 2026 | pond 8 | NA - refer to Report Details | Under investigation |
| Oct 8, 2025 | Huichica (HCU) Pond 8 near entrance on Milton Rd | Danger | Advisory based on visual and toxins; Advisory due to historical data. |
| Oct 8, 2025 | Huichica Creek Wildlife Area near entrance on Buchli Station Rd | Danger | Advisory based on visual and toxins; Advisory due to historical data. |
| Sep 15, 2025 | Huichica Creek Wildlife Area near entrance on Buchli Station Rd | Danger | Advisory due to historical data. |
| Sep 15, 2025 | Huichica (HCU) Pond 8 near entrance on Milton Rd | Danger | Advisory due to historical data. |
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.