Bridgeport Reservoir: toxic algae advisories
Bridgeport Reservoir, Mono County. See all Mono County waters.
What the state's records say
Danger advisory, last posted Oct 20, 2026. No all-clear recorded.
9 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 Bridgeport Reservoir
The state has an advisory on file for Bridgeport Reservoir (Danger advisory), last posted Oct 20, 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.
Satellite estimate (not an advisory)
Week ending Oct 10, 2026: about 520,000 cells/mL of cyanobacteria near the center of Bridgeport Reservoir.
A satellite estimate from EPA CyAN for a 6.5 km² lake. It does not measure toxins and does not change the advisory status.
| Week ending | Estimate |
|---|---|
| Oct 10, 2026 | about 520,000 cells/mL |
| Oct 3, 2026 | about 520,000 cells/mL |
| Sep 26, 2026 | about 390,000 cells/mL |
| Sep 19, 2026 | about 100,000 cells/mL |
| Sep 12, 2026 | about 180,000 cells/mL |
| Sep 5, 2026 | about 1,200,000 cells/mL |
| Aug 29, 2026 | about 1,100,000 cells/mL |
| Aug 22, 2026 | about 960,000 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 |
|---|---|
| North East Corner of Dam | Caution advisory, last posted Oct 20, 2026. No all-clear recorded. |
| Old Marina Boat Ramp | Caution advisory, last posted Oct 20, 2026. No all-clear recorded. |
| RV Park | Caution advisory, last posted Oct 20, 2026. No all-clear recorded. |
| Paradise Shore RV Camp | Caution advisory, last posted Jul 11, 2024. No all-clear recorded. |
| Old Marina Ramp | The state's latest record, from Oct 19, 2022, recommends no advisory. |
| RV Park | Caution advisory, last posted Oct 19, 2022. No all-clear recorded. |
| North East Corner of Dam | Danger advisory, last posted Oct 19, 2022. No all-clear recorded. |
| Bay South of Mono Co. Boat Ramp | The state's latest record, from Jun 21, 2022, recommends no advisory. |
| Spot not described | Caution advisory, last posted Jul 1, 2021. No all-clear recorded. |
| shore zone west of marina | The state's latest record, from Jul 1, 2021, recommends no advisory. |
| boat launch northeast shore | The state's latest record, from Jul 1, 2021, recommends no advisory. |
| Bridgeport Reservoir, boat launch | Caution advisory, last posted Aug 31, 2020. No all-clear recorded. |
| Bridgeport Reservoir, near marina | Caution advisory, last posted Aug 31, 2020. No all-clear recorded. |
Advisory history
Every advisory record the state has published for Bridgeport 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 |
|---|---|---|---|
| Oct 20, 2026 | North East Corner of Dam | Caution | Advisory based on visual and toxins |
| Oct 20, 2026 | Old Marina Boat Ramp | Caution | Advisory based on visual and toxins |
| Oct 20, 2026 | Old Marina Boat Ramp | Caution | Advisory based on visual and toxins |
| Oct 20, 2026 | RV Park | Caution | Advisory based on visual and toxins |
| Sep 2, 2026 | RV Park | Visual observation | Visual monitoring only-present bloom |
| Sep 2, 2026 | Old Marina Boat Ramp | Danger | Advisory based on visual and toxins |
| Sep 2, 2026 | North East Corner of Dam | Danger | Advisory based on visual and toxins |
| Jun 24, 2026 | RV Park | None | Advisory based on visual and toxins; Floating/planktonic bloom observed |
| Jun 24, 2026 | North East Corner of Dam | Visual observation | Advisory based on visual and toxins |
| Jun 24, 2026 | Old Marina Boat Ramp | None | Advisory based on visual and toxins |
| Jun 24, 2026 | Old Marina Boat Ramp | Caution | Advisory based on visual and toxins |
| Jun 24, 2026 | North East Corner of Dam | Caution | Advisory based on visual and toxins |
| Oct 10, 2025 | North East Corner of Dam | Warning | Advisory based on visual and toxins |
| Oct 10, 2025 | RV Park | Warning | Advisory based on visual and toxins; Floating/planktonic bloom observed |
| Oct 10, 2025 | Old Marina Boat Ramp | Danger | Advisory based on visual and toxins; Floating/planktonic bloom observed |
| Oct 10, 2025 | North East Corner of Dam | Danger | Advisory based on visual and toxins |
| Aug 21, 2025 | North East Corner of Dam | Danger | Advisory based on visual and toxins |
| Aug 21, 2025 | Old Marina Boat Ramp | Danger | Advisory based on visual and toxins; Floating/planktonic bloom observed |
| Aug 21, 2025 | RV Park | Warning | Advisory based on visual and toxins; Floating/planktonic bloom observed |
| Jun 25, 2025 | RV Park | Visual observation | Advisory based on visual and toxins; Floating/planktonic bloom observed |
| Jun 25, 2025 | Old Marina Boat Ramp | Visual observation | Advisory based on visual and toxins; Floating/planktonic bloom observed |
| Jun 25, 2025 | North East Corner of Dam | Caution | Advisory based on visual and toxins |
| Oct 2, 2024 | RV Park | Danger | Advisory based on visual and toxins; Floating/planktonic bloom observed |
| Oct 2, 2024 | Old Marina Boat Ramp | Visual observation | Advisory based on visual and toxins; Floating/planktonic bloom observed |
| Oct 2, 2024 | North East Corner of Dam | Danger | Advisory based on visual and toxins |
| Oct 1, 2024 | North East Corner of Dam | Visual observation | Advisory based on visual and toxins; Updates from routine monitoring program-organization |
| Oct 1, 2024 | Old Marina Boat Ramp | Visual observation | Floating/planktonic bloom observed |
| Oct 1, 2024 | RV Park | Visual observation | Floating/planktonic bloom observed |
| Aug 27, 2024 | RV Park | Visual observation | Floating/planktonic bloom observed |
| Aug 27, 2024 | Old Marina Boat Ramp | Visual observation | Floating/planktonic bloom observed |
| Aug 27, 2024 | North East Corner of Dam | Caution | Advisory based on visual and toxins; Updates from routine monitoring program-organization |
| Jul 11, 2024 | Paradise Shore RV Camp | Caution | Suspected illness reported; Under investigation |
| Jul 3, 2024 | Paradise Shore RV Camp | Caution | Suspected illness reported; Under investigation |
| Jul 2, 2024 | Paradise Shore RV Camp | NA - refer to Report Details | Suspected illness reported; Under investigation |
| Jun 20, 2024 | RV Park | None | Advisory based on visual and toxins; Testing results below posting triggers |
| Jun 20, 2024 | Old Marina Boat Ramp | None | Testing results below posting triggers |
| Jun 20, 2024 | North East Corner of Dam | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Oct 11, 2023 | RV Park | Visual observation | Advisory based on visual and toxins; Updates from routine monitoring program-organization |
| Oct 11, 2023 | Old Marina Boat Ramp | Visual observation | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Oct 11, 2023 | North East Corner of Dam | Visual observation | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Oct 11, 2023 | North East Corner of Dam | Visual observation | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Oct 11, 2023 | Old Marina Boat Ramp | Visual observation | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Oct 11, 2023 | RV Park | Visual observation | Advisory based on visual and toxins; Updates from routine monitoring program-organization |
| Oct 11, 2023 | Old Marina Boat Ramp | Caution | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Oct 11, 2023 | North East Corner of Dam | Caution | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 24, 2023 | Old Marina Boat Ramp | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 24, 2023 | North East Corner of Dam | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 21, 2023 | RV Park | None | Advisory based on visual and toxins; Updates from routine monitoring program-organization |
| Jun 21, 2023 | RV Park | None | Advisory based on visual and toxins; Updates from routine monitoring program-organization |
| Jun 21, 2023 | Old Marina Boat Ramp | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 21, 2023 | North East Corner of Dam | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Oct 19, 2022 | Old Marina Ramp | None | End date recorded: Dec 27, 2022. Testing results below posting triggers |
| Oct 19, 2022 | Old Marina Ramp | None | Testing results below posting triggers |
| Oct 19, 2022 | RV Park | Caution | Advisory based on visual and toxins |
| Oct 19, 2022 | North East Corner of Dam | Danger | Advisory based on visual and toxins; Alert-high concentration toxins |
| Aug 31, 2022 | North East Corner of Dam | Danger | Advisory based on visual and toxins; Alert-high concentration toxins |
| Aug 31, 2022 | RV Park | Caution | Advisory based on visual and toxins |
| Jun 21, 2022 | North East Corner of Dam | None | Testing results below posting triggers |
| Jun 21, 2022 | Old Marina Ramp | None | Testing results below posting triggers |
| Jun 21, 2022 | Bay South of Mono Co. Boat Ramp | None | Testing results below posting triggers |
| Jun 21, 2022 | RV Park | None | Testing results below posting triggers |
| Jun 3, 2022 | North East Corner of Dam | None | Testing results below posting triggers |
| Jun 3, 2022 | Old Marina Ramp | None | Testing results below posting triggers |
| Jun 3, 2022 | Bay South of Mono Co. Boat Ramp | None | Testing results below posting triggers |
| Jun 3, 2022 | RV Park | None | Testing results below posting triggers |
| Jul 1, 2021 | Spot not described | Caution | Advisory based on visual and toxins |
| Jul 1, 2021 | shore zone west of marina | None | Testing results below posting triggers |
| Jul 1, 2021 | boat launch northeast shore | None | Testing results below posting triggers |
| Aug 31, 2020 | Bridgeport Reservoir, boat launch | Caution | Advisory based on visual and toxins |
| Aug 31, 2020 | Bridgeport Reservoir, near marina | Caution | 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.