Contra Loma Reservoir: toxic algae advisories
Contra Loma Reservoir, Contra Costa County. See all Contra Costa County waters.
What the state's records say
Caution advisory, last posted Dec 8, 2022. 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: 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 Contra Loma Reservoir
The state has an advisory on file for Contra Loma Reservoir (Caution advisory), last posted Dec 8, 2022, 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 |
|---|---|
| Contra Loma Reservoir, at Regional Park | The state's latest record, from Sep 25, 2026, recommends no advisory. |
| at Regional Park | Caution advisory, last posted Dec 8, 2022. No all-clear recorded. |
| at Regional Park | Caution advisory, last posted Apr 15, 2022. No all-clear recorded. |
| at Regional Park | The state's latest record, from Jul 16, 2021, recommends no advisory. |
| Contra Loma Reservoir, at Regional Park | The state's latest record, from Jul 10, 2021, recommends no advisory. |
Advisory history
Every advisory record the state has published for Contra Loma 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 |
|---|---|---|---|
| Sep 25, 2026 | Contra Loma Reservoir, at Regional Park | None | Updates from routine monitoring program-organization |
| Sep 18, 2026 | Contra Loma Reservoir, at Regional Park | None | Updates from routine monitoring program-organization |
| Sep 3, 2026 | Contra Loma Reservoir, at Regional Park | None | Updates from routine monitoring program-organization |
| Aug 31, 2026 | Contra Loma Reservoir, at Regional Park | None | Updates from routine monitoring program-organization |
| Aug 14, 2026 | Contra Loma Reservoir, at Regional Park | None | Updates from routine monitoring program-organization |
| Jul 31, 2026 | Contra Loma Reservoir, at Regional Park | None | Updates from routine monitoring program-organization |
| Jul 3, 2026 | Contra Loma Reservoir, at Regional Park | None | Updates from routine monitoring program-organization |
| Jun 19, 2026 | Contra Loma Reservoir, at Regional Park | None | Updates from routine monitoring program-organization |
| May 26, 2026 | Contra Loma Reservoir, at Regional Park | None | Updates from routine monitoring program-organization |
| May 8, 2026 | Contra Loma Reservoir, at Regional Park | None | Lake-wide advisory; Updates from routine monitoring program-organization |
| May 1, 2026 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Apr 24, 2026 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Apr 13, 2026 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Mar 20, 2026 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jan 21, 2026 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Dec 5, 2025 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Nov 6, 2025 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Oct 10, 2025 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Oct 10, 2025 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Oct 6, 2025 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Sep 11, 2025 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Sep 5, 2025 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Aug 28, 2025 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Aug 22, 2025 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Aug 18, 2025 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Aug 7, 2025 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jul 31, 2025 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jul 24, 2025 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jul 11, 2025 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jun 26, 2025 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jun 20, 2025 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jun 6, 2025 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| May 23, 2025 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| May 23, 2025 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| May 9, 2025 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Apr 18, 2025 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Apr 11, 2025 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Apr 4, 2025 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Mar 21, 2025 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Mar 21, 2025 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Mar 14, 2025 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Mar 14, 2025 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Mar 7, 2025 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Feb 27, 2025 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Feb 21, 2025 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Feb 6, 2025 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jan 31, 2025 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jan 24, 2025 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jan 17, 2025 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jan 13, 2025 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jan 2, 2025 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Dec 20, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Dec 5, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Dec 5, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Dec 2, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Oct 31, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Oct 25, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Oct 17, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Oct 11, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Oct 4, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Sep 27, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Sep 27, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Sep 20, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Sep 13, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Aug 23, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Aug 15, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Aug 1, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jul 22, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jun 21, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jun 14, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jun 7, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| May 24, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Advisory based on visual and toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| May 10, 2024 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| May 3, 2024 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Apr 26, 2024 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Apr 19, 2024 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Apr 12, 2024 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Mar 29, 2024 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Mar 21, 2024 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Mar 15, 2024 | Contra Loma Reservoir, at Regional Park | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Feb 29, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Feb 19, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Lake-wide advisory; Updates from routine monitoring program-organization |
| Feb 9, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Advisory based on visual and toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Feb 2, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Advisory based on visual and toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Jan 19, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Advisory based on visual and toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Jan 12, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Advisory based on visual and toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Jan 5, 2024 | Contra Loma Reservoir, at Regional Park | Danger | Advisory based on visual and toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Dec 22, 2023 | Contra Loma Reservoir, at Regional Park | Danger | Advisory based on visual and toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Dec 1, 2023 | Contra Loma Reservoir, at Regional Park | Danger | Advisory based on visual and toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Nov 20, 2023 | Contra Loma Reservoir, at Regional Park | Danger | Advisory based on visual and toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Oct 19, 2023 | Contra Loma Reservoir, at Regional Park | Danger | Advisory based on visual and toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Oct 5, 2023 | Contra Loma Reservoir, at Regional Park | Danger | Advisory based on visual and toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Sep 22, 2023 | Contra Loma Reservoir, at Regional Park | Danger | Advisory based on visual and toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Aug 25, 2023 | Contra Loma Reservoir, at Regional Park | Danger | Advisory based on visual and toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Aug 10, 2023 | Contra Loma Reservoir, at Regional Park | Danger | Advisory based on visual and toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Aug 7, 2023 | Contra Loma Reservoir, at Regional Park | Danger | Advisory based on visual and toxins; Updates from routine monitoring program-organization |
| Jul 28, 2023 | Contra Loma Reservoir, at Regional Park | Caution | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 19, 2023 | Contra Loma Reservoir, at Regional Park | Caution | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 6, 2023 | Contra Loma Reservoir, at Regional Park | Visual observation | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 28, 2023 | Contra Loma Reservoir, at Regional Park | Visual observation | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 2, 2023 | Contra Loma Reservoir, at Regional Park | Visual observation | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 2, 2023 | Contra Loma Reservoir, at Regional Park | Caution | Updates from routine monitoring program-organization |
| May 28, 2023 | Contra Loma Reservoir, at Regional Park | None | Updates from routine monitoring program-organization |
| Apr 28, 2023 | Contra Loma Reservoir, at Regional Park | None | Updates from routine monitoring program-organization |
| Apr 18, 2023 | Contra Loma Reservoir, at Regional Park | None | Updates from routine monitoring program-organization |
| Apr 5, 2023 | Contra Loma Reservoir, at Regional Park | None | Updates from routine monitoring program-organization |
| Mar 29, 2023 | Contra Loma Reservoir, at Regional Park | None | Updates from routine monitoring program-organization |
| Mar 8, 2023 | Contra Loma Reservoir, at Regional Park | None | Updates from routine monitoring program-organization |
| Feb 14, 2023 | Contra Loma Reservoir, at Regional Park | None | Updates from routine monitoring program-organization |
| Feb 3, 2023 | Contra Loma Reservoir, at Regional Park | Caution | Updates from routine monitoring program-organization |
| Jan 27, 2023 | Contra Loma Reservoir, at Regional Park | Caution | Updates from routine monitoring program-organization |
| Dec 8, 2022 | at Regional Park | Caution | Floating/planktonic bloom observed |
| Dec 2, 2022 | at Regional Park | Caution | Floating/planktonic bloom observed |
| Nov 28, 2022 | at Regional Park | Caution | Floating/planktonic bloom observed |
| Nov 18, 2022 | at Regional Park | Caution | Floating/planktonic bloom observed |
| Nov 14, 2022 | at Regional Park | Caution | Floating/planktonic bloom observed |
| Nov 10, 2022 | at Regional Park | Caution | Floating/planktonic bloom observed |
| Nov 4, 2022 | at Regional Park | Caution | Floating/planktonic bloom observed |
| Oct 27, 2022 | at Regional Park | Caution | Floating/planktonic bloom observed |
| Oct 27, 2022 | at Regional Park | Caution | Floating/planktonic bloom observed |
| Oct 19, 2022 | at Regional Park | Caution | Floating/planktonic bloom observed |
| Oct 17, 2022 | at Regional Park | Caution | Floating/planktonic bloom observed |
| Oct 7, 2022 | at Regional Park | Danger | Advisory based on visual and toxins; Floating/planktonic bloom observed; Updates from routine monitoring program-organization |
| Sep 30, 2022 | at Regional Park | Danger | Advisory based on visual and toxins; Floating/planktonic bloom observed; Updates from routine monitoring program-organization |
| Sep 26, 2022 | at Regional Park | Danger | Advisory based on visual and toxins; Floating/planktonic bloom observed; Updates from routine monitoring program-organization |
| Sep 16, 2022 | at Regional Park | Caution | Advisory based on visual and toxins; Floating/planktonic bloom observed; Updates from routine monitoring program-organization |
| Sep 8, 2022 | at Regional Park | Caution | Advisory based on visual and toxins; Floating/planktonic bloom observed; Updates from routine monitoring program-organization |
| Sep 1, 2022 | at Regional Park | Caution | Advisory based on visual and toxins; Floating/planktonic bloom observed; Updates from routine monitoring program-organization |
| Aug 26, 2022 | at Regional Park | Caution | Advisory based on visual and toxins; Floating/planktonic bloom observed; Updates from routine monitoring program-organization |
| Aug 19, 2022 | at Regional Park | Caution | Advisory based on visual and toxins; Floating/planktonic bloom observed; Updates from routine monitoring program-organization |
| Aug 10, 2022 | at Regional Park | Caution | Advisory based on visual and toxins; Floating/planktonic bloom observed |
| Aug 10, 2022 | at Regional Park | Caution | Advisory based on visual and toxins |
| Aug 5, 2022 | at Regional Park | Caution | Advisory based on visual and toxins |
| Aug 2, 2022 | at Regional Park | Caution | Advisory based on visual and toxins |
| Jul 22, 2022 | at Regional Park | Caution | Advisory based on visual and toxins |
| Jul 15, 2022 | at Regional Park | Caution | Advisory based on visual and toxins |
| Jul 14, 2022 | at Regional Park | Caution | Advisory based on visual and toxins |
| Jul 1, 2022 | at Regional Park | None | Advisory based on visual and toxins |
| Jun 27, 2022 | at Regional Park | Caution | Advisory based on visual and toxins |
| Jun 17, 2022 | at Regional Park | Caution | Advisory based on visual and toxins |
| Jun 10, 2022 | at Regional Park | Caution | Advisory based on visual and toxins |
| May 27, 2022 | at Regional Park | Caution | Advisory based on visual and toxins |
| May 19, 2022 | at Regional Park | Caution | Advisory based on visual and toxins |
| May 12, 2022 | at Regional Park | Caution | Advisory based on visual and toxins |
| May 6, 2022 | at Regional Park | Caution | Advisory based on visual and toxins |
| Apr 15, 2022 | at Regional Park | Caution | Advisory based on visual and toxins |
| Jul 16, 2021 | at Regional Park | None | Testing results below posting triggers |
| Jul 10, 2021 | Contra Loma Reservoir, at Regional Park | 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.