Tulloch Reservoir: toxic algae advisories
Tulloch Reservoir, Calaveras County. See all Calaveras County waters.
What the state's records say
Reports on file, with no advisory level the state has classified.
That reflects what the state knew on that date. It is not a finding that the water is safe now: blooms can return within days, and many are never reported.
Before you go, check the state's official algae page and any signs posted at the water.
Dogs at Tulloch Reservoir
The state has reports on file for Tulloch Reservoir but has not classified an advisory level, so the records cannot answer this. Keep your dog out of discolored or scummy water.
Satellite estimate (not an advisory)
Week ending Feb 1, 2025: about 470,000 cells/mL of cyanobacteria near the center of Tulloch Reservoir.
A satellite estimate from EPA CyAN for a 3.8 km² lake. It does not measure toxins and does not change the advisory status.
| Week ending | Estimate |
|---|---|
| Feb 1, 2025 | about 470,000 cells/mL |
| Jan 25, 2025 | about 400,000 cells/mL |
| Jan 11, 2025 | about 210,000 cells/mL |
| Feb 15, 2020 | about 310,000 cells/mL |
This is a satellite estimate from the U.S. EPA's Cyanobacteria Assessment Network, not an advisory. It estimates how much cyanobacteria is in the water near the lake's center, not whether toxins are present: a high number does not mean toxins, and a low one does not mean there are none. It covers lakes of about 1 square kilometer and larger, so small ponds, dog parks and most rivers are not covered, and clouds can hide a lake for weeks. It never changes the advisory status above.
Satellite estimates: U.S. EPA Cyanobacteria Assessment Network (CyAN), from Copernicus Sentinel-3 data. Provisional, research-level estimates; EPA does not endorse this site. Checked Oct 22, 2026.
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 |
|---|---|
| near Sanguinetti Court | Reports on file, with no advisory level the state has classified. |
Advisory history
Every advisory record the state has published for Tulloch 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 |
|---|---|---|---|
| Jun 8, 2026 | near Sanguinetti Court | NA - refer to Report Details | No cyano bloom w/photos |
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.