Middle River: toxic algae advisories
Middle River, San Joaquin County. See all San Joaquin County waters.
What the state's records say
Caution advisory, last posted Jul 24, 2026. No all-clear recorded.
3 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 Middle River
The state has an advisory on file for Middle River (Caution advisory), last posted Jul 24, 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 |
|---|---|
| Middle River at Tracy (MRX) | Visual observation, last posted Jul 24, 2026. No all-clear recorded. |
| Middle River at Undine (MRU) | The state's latest record, from Jul 24, 2026, recommends no advisory. |
| Middle River at Howard Rd (MHO) | The state's latest record, from Jul 24, 2026, recommends no advisory. |
| near Mildred Island (HLT) | Visual observation, last posted Oct 26, 2023. No all-clear recorded. |
| near Mildred Island (HLT) | The state's latest record, from Dec 30, 2022, recommends no advisory. |
| at Tracy (MRX) | The state's latest record, from Dec 8, 2022, recommends no advisory. |
| at Undine (MRU) | The state's latest record, from Dec 8, 2022, recommends no advisory. |
| at Howard Road (MHO) | The state's latest record, from Dec 8, 2022, recommends no advisory. |
| South of Kaketan Island | The state's latest record, from Sep 1, 2022, recommends no advisory. |
| near Mildred Island | The state's latest record, from Nov 10, 2021, recommends no advisory. |
| at Mildred Island | Caution advisory, last posted Jul 20, 2021. No all-clear recorded. |
| Middle River near Holt, Turner cut near Holt | Reports on file, with no advisory level the state has classified. |
| Middle River near upstream of West Undine Road | The state's latest record, from Dec 4, 2018, recommends no advisory. |
| Middle River at Victoria Canal Confluence near Union Point | The state's latest record, from Dec 4, 2018, recommends no advisory. |
| Middle River downstream of S Tracy Boulevard | The state's latest record, from Dec 4, 2018, recommends no advisory. |
Advisory history
Every advisory record the state has published for Middle 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 |
|---|---|---|---|
| Jul 24, 2026 | Middle River at Tracy (MRX) | Visual observation | Updates from routine monitoring program-organization; Visual monitoring only-present bloom |
| Jul 24, 2026 | Middle River at Undine (MRU) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jul 24, 2026 | Middle River at Howard Rd (MHO) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jul 8, 2026 | Middle River at Tracy (MRX) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jul 8, 2026 | Middle River at Undine (MRU) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jul 8, 2026 | Middle River at Howard Rd (MHO) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| May 27, 2026 | Middle River at Tracy (MRX) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| May 27, 2026 | Middle River at Undine (MRU) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| May 27, 2026 | Middle River at Howard Rd (MHO) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Apr 29, 2026 | Middle River at Tracy (MRX) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Apr 29, 2026 | Middle River at Undine (MRU) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Apr 29, 2026 | Middle River at Howard Rd (MHO) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Feb 6, 2026 | Middle River at Tracy (MRX) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Feb 6, 2026 | Middle River at Undine (MRU) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Feb 6, 2026 | Middle River at Howard Rd (MHO) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Feb 6, 2026 | Middle River at Tracy (MRX) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Feb 6, 2026 | Middle River at Undine (MRU) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Feb 6, 2026 | Middle River at Howard Rd (MHO) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Sep 24, 2025 | Middle River at Tracy (MRX) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Sep 24, 2025 | Middle River at Undine (MRU) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Sep 24, 2025 | Middle River at Howard Rd (MHO) | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 18, 2025 | Middle River at Tracy (MRX) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Aug 18, 2025 | Middle River at Undine (MRU) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Aug 18, 2025 | Middle River at Howard Rd (MHO) | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 30, 2025 | Middle River at Undine (MRU) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jul 30, 2025 | Middle River at Tracy (MRX) | Visual observation | Updates from routine monitoring program-organization; Visual monitoring only-present bloom |
| Jul 30, 2025 | Middle River at Howard Rd (MHO) | Visual observation | Updates from routine monitoring program-organization; Visual monitoring only-present bloom |
| Jul 30, 2025 | Middle River at Howard Rd (MHO) | Visual observation | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jun 23, 2025 | Middle River at Tracy (MRX) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jun 23, 2025 | Middle River at Undine (MRU) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jun 23, 2025 | Middle River at Howard Rd (MHO) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jun 12, 2025 | Middle River at Tracy (MRX) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jun 12, 2025 | Middle River at Undine (MRU) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jun 12, 2025 | Middle River at Howard Rd (MHO) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jun 3, 2025 | Middle River at Tracy (MRX) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jun 3, 2025 | Middle River at Undine (MRU) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jun 3, 2025 | Middle River at Howard Rd (MHO) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Mar 25, 2025 | Middle River at Tracy (MRX) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Mar 25, 2025 | Middle River at Undine (MRU) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Mar 25, 2025 | Middle River at Howard Rd (MHO) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Feb 26, 2025 | Middle River at Tracy (MRX) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Feb 26, 2025 | Middle River at Undine (MRU) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Feb 26, 2025 | Middle River at Howard Rd (MHO) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Feb 19, 2025 | Middle River at Tracy (MRX) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Feb 19, 2025 | Middle River at Undine (MRU) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Feb 19, 2025 | Middle River at Howard Rd (MHO) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Dec 17, 2024 | Middle River at Tracy (MRX) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Dec 17, 2024 | Middle River at Undine (MRU) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Dec 17, 2024 | Middle River at Howard Rd (MHO) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Nov 13, 2024 | Middle River at Tracy (MRX) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Nov 13, 2024 | Middle River at Undine (MRU) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Nov 13, 2024 | Middle River at Howard Rd (MHO) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Oct 11, 2024 | Middle River at Tracy (MRX) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Oct 11, 2024 | Middle River at Undine (MRU) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Oct 11, 2024 | Middle River at Howard Rd (MHO) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Aug 27, 2024 | Middle River at Tracy (MRX) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Aug 27, 2024 | Middle River at Howard Rd (MHO) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Aug 27, 2024 | Middle River at Undine (MRU) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Aug 27, 2024 | Middle River at Howard Rd (MHO) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Aug 8, 2024 | Middle River at Tracy (MRX) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Aug 8, 2024 | Middle River at Undine (MRU) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Aug 8, 2024 | Middle River at Howard Rd (MHO) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| May 3, 2024 | Middle River at Tracy (MRX) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| May 3, 2024 | Middle River at Undine (MRU) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| May 3, 2024 | Middle River at Howard Rd (MHO) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Mar 22, 2024 | Middle River at Tracy (MRX) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Mar 22, 2024 | Middle River at Undine (MRU) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Mar 22, 2024 | Middle River at Howard Rd (MHO) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Feb 27, 2024 | Middle River at Tracy (MRX) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Feb 27, 2024 | Middle River at Undine (MRU) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Feb 27, 2024 | Middle River at Howard Rd (MHO) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jan 25, 2024 | Middle River at Tracy (MRX) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jan 25, 2024 | Middle River at Undine (MRU) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jan 25, 2024 | Middle River at Howard Rd (MHO) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Dec 21, 2023 | Middle River at Tracy (MRX) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Dec 21, 2023 | Middle River at Undine (MRU) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Dec 21, 2023 | Middle River at Howard Rd (MHO) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Dec 1, 2023 | Middle River at Tracy (MRX) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Dec 1, 2023 | Middle River at Undine (MRU) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Dec 1, 2023 | Middle River at Howard Rd (MHO) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Oct 26, 2023 | near Mildred Island (HLT) | Visual observation | Updates from routine monitoring program-organization; Visual monitoring only-present bloom |
| Sep 27, 2023 | Middle River at Undine (MRU) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Sep 27, 2023 | Middle River at Tracy (MRX) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Sep 27, 2023 | Middle River at Howard Rd (MHO) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Sep 13, 2023 | near Mildred Island (HLT) | Visual observation | Updates from routine monitoring program-organization; Visual monitoring only-present bloom |
| Aug 22, 2023 | Middle River at Tracy (MRX) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Aug 22, 2023 | Middle River at Undine (MRU) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Aug 22, 2023 | Middle River at Howard Rd (MHO) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Aug 1, 2023 | near Mildred Island (HLT) | Visual observation | Updates from routine monitoring program-organization; Visual monitoring only-present bloom |
| Jul 28, 2023 | Middle River at Tracy (MRX) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jul 28, 2023 | Middle River at Undine (MRU) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jul 28, 2023 | Middle River at Howard Rd (MHO) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jun 20, 2023 | Middle River at Tracy (MRX) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jun 20, 2023 | Middle River at Undine (MRU) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jun 20, 2023 | Middle River at Howard Rd (MHO) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jun 9, 2023 | near Mildred Island (HLT) | None | Updates from routine monitoring program-organization; visual monitoring based advisory; Visual monitoring only-absent bloom |
| May 26, 2023 | Middle River at Howard Rd (MHO) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| May 26, 2023 | Middle River at Undine (MRU) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| May 26, 2023 | Middle River at Undine (MRU) | Visual observation | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| May 26, 2023 | Middle River at Howard Rd (MHO) | Visual observation | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| May 26, 2023 | Middle River at Howard Rd (MHO) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| May 26, 2023 | Middle River at Undine (MRU) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| May 26, 2023 | Middle River at Tracy (MRX) | NA - refer to Report Details | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| May 26, 2023 | Middle River at Tracy (MRX) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| May 26, 2023 | Middle River at Undine (MRU) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| May 26, 2023 | Middle River at Howard Rd (MHO) | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| May 26, 2023 | Middle River at Howard Rd (MHO) | None | Updates from routine monitoring program-organization; visual monitoring based advisory |
| May 26, 2023 | Middle River at Tracy (MRX) | None | Updates from routine monitoring program-organization; visual monitoring based advisory |
| May 26, 2023 | Middle River at Undine (MRU) | None | Updates from routine monitoring program-organization; visual monitoring based advisory |
| Apr 20, 2023 | near Mildred Island (HLT) | None | Updates from routine monitoring program-organization; visual monitoring based advisory |
| Apr 11, 2023 | Middle River at Tracy (MRX) | None | Updates from routine monitoring program-organization; visual monitoring based advisory |
| Apr 11, 2023 | Middle River at Undine (MRU) | None | Updates from routine monitoring program-organization; visual monitoring based advisory |
| Apr 11, 2023 | Middle River at Howard Rd (MHO) | None | Updates from routine monitoring program-organization; visual monitoring based advisory |
| Mar 20, 2023 | Middle River at Tracy (MRX) | None | Updates from routine monitoring program-organization; visual monitoring based advisory |
| Mar 20, 2023 | Middle River at Undine (MRU) | None | Updates from routine monitoring program-organization; visual monitoring based advisory |
| Mar 20, 2023 | Middle River at Howard Rd (MHO) | None | Updates from routine monitoring program-organization; visual monitoring based advisory |
| Mar 2, 2023 | near Mildred Island (HLT) | None | Updates from routine monitoring program-organization; visual monitoring based advisory |
| Jan 31, 2023 | near Mildred Island (HLT) | None | Updates from routine monitoring program-organization; visual monitoring based advisory |
| Jan 18, 2023 | Middle River at Tracy (MRX) | None | Updates from routine monitoring program-organization |
| Jan 18, 2023 | Middle River at Undine (MRU) | None | Updates from routine monitoring program-organization |
| Jan 18, 2023 | Middle River at Howard Rd (MHO) | None | Updates from routine monitoring program-organization |
| Jan 1, 2023 | near Mildred Island (HLT) | None | Updates from routine monitoring program-organization |
| Dec 30, 2022 | near Mildred Island (HLT) | None | Updates from routine monitoring program-organization |
| Dec 8, 2022 | at Tracy (MRX) | None | End date recorded: Oct 25, 2022. Updates from routine monitoring program-organization; visual monitoring based advisory |
| Dec 8, 2022 | at Undine (MRU) | None | End date recorded: Oct 25, 2022. Updates from routine monitoring program-organization; visual monitoring based advisory |
| Dec 8, 2022 | at Howard Road (MHO) | None | End date recorded: Oct 25, 2022. Updates from routine monitoring program-organization; visual monitoring based advisory |
| Nov 16, 2022 | at Tracy (MRX) | None | End date recorded: Oct 25, 2022. Updates from routine monitoring program-organization; visual monitoring based advisory |
| Nov 16, 2022 | at Undine (MRU) | None | End date recorded: Oct 25, 2022. Updates from routine monitoring program-organization; visual monitoring based advisory |
| Nov 16, 2022 | at Howard Road (MHO) | None | End date recorded: Oct 25, 2022. Updates from routine monitoring program-organization; visual monitoring based advisory |
| Oct 25, 2022 | at Tracy (MRX) | None | End date recorded: Oct 25, 2022. Floating/planktonic bloom observed; Updates from routine monitoring program-organization; visual monitoring based advisory |
| Oct 25, 2022 | at Undine (MRU) | None | End date recorded: Oct 25, 2022. Updates from routine monitoring program-organization; visual monitoring based advisory |
| Oct 25, 2022 | at Howard Road (MHO) | None | End date recorded: Oct 25, 2022. Updates from routine monitoring program-organization; visual monitoring based advisory |
| Oct 21, 2022 | near Mildred Island (HLT) | Caution | Updates from routine monitoring program-organization |
| Sep 19, 2022 | near Mildred Island (HLT) | Caution | Updates from routine monitoring program-organization |
| Sep 15, 2022 | at Tracy (MRX) | Caution | Floating/planktonic bloom observed; Updates from routine monitoring program-organization; visual monitoring based advisory |
| Sep 15, 2022 | at Undine (MRU) | Caution | Floating/planktonic bloom observed; Updates from routine monitoring program-organization; visual monitoring based advisory |
| Sep 15, 2022 | at Howard Road (MHO) | Caution | Floating/planktonic bloom observed; Updates from routine monitoring program-organization; visual monitoring based advisory |
| Sep 1, 2022 | South of Kaketan Island | None | |
| Aug 18, 2022 | at Tracy (MRX) | Caution | Floating/planktonic bloom observed; Updates from routine monitoring program-organization; visual monitoring based advisory |
| Aug 18, 2022 | at Undine (MRU) | None | Floating/planktonic bloom observed; Updates from routine monitoring program-organization; visual monitoring based advisory |
| Aug 18, 2022 | at Howard Road (MHO) | Caution | Floating/planktonic bloom observed; Updates from routine monitoring program-organization; visual monitoring based advisory |
| Aug 1, 2022 | at Tracy (MRX) | Caution | Updates from routine monitoring program-organization |
| Aug 1, 2022 | at Undine (MRU) | None | Updates from routine monitoring program-organization |
| Aug 1, 2022 | at Howard Road (MHO) | Caution | Updates from routine monitoring program-organization |
| Jul 20, 2022 | at Tracy (MRX) | None | Updates from routine monitoring program-organization |
| Jul 20, 2022 | at Undine (MRU) | None | Updates from routine monitoring program-organization |
| Jul 20, 2022 | at Howard Road (MHO) | None | Updates from routine monitoring program-organization |
| Jun 23, 2022 | at Tracy (MRX) | Caution | Updates from routine monitoring program-organization |
| Jun 23, 2022 | at Undine (MRU) | Caution | Updates from routine monitoring program-organization |
| Jun 23, 2022 | at Howard Road (MHO) | Caution | Updates from routine monitoring program-organization |
| Jun 21, 2022 | at Undine (MRU) | Caution | Updates from routine monitoring program-organization |
| Jun 21, 2022 | at Tracy (MRX) | Caution | Updates from routine monitoring program-organization |
| Jun 21, 2022 | at Howard Road (MHO) | Caution | Updates from routine monitoring program-organization |
| Jun 16, 2022 | near Mildred Island (HLT) | Caution | Updates from routine monitoring program-organization |
| Jun 16, 2022 | near Mildred Island (HLT) | Caution | Updates from routine monitoring program-organization |
| May 25, 2022 | at Howard Road (MHO) | None | Updates from routine monitoring program-organization |
| May 25, 2022 | at Undine (MRU) | None | Updates from routine monitoring program-organization |
| May 25, 2022 | at Tracy (MRX) | None | Updates from routine monitoring program-organization |
| May 18, 2022 | near Mildred Island (HLT) | None | Updates from routine monitoring program-organization |
| May 4, 2022 | near Mildred Island (HLT) | None | Updates from routine monitoring program-organization |
| Apr 19, 2022 | at Howard Road (MHO) | None | Updates from routine monitoring program-organization |
| Apr 19, 2022 | at Undine (MRU) | None | Updates from routine monitoring program-organization |
| Apr 19, 2022 | at Tracy (MRX) | None | Updates from routine monitoring program-organization |
| Apr 19, 2022 | near Mildred Island (HLT) | None | Updates from routine monitoring program-organization |
| Mar 30, 2022 | at Undine (MRU) | None | Updates from routine monitoring program-organization |
| Mar 30, 2022 | at Tracy (MRX) | None | Updates from routine monitoring program-organization |
| Mar 30, 2022 | at Howard Road (MHO) | None | Updates from routine monitoring program-organization |
| Mar 4, 2022 | near Mildred Island (HLT) | None | Updates from routine monitoring program-organization |
| Nov 10, 2021 | near Mildred Island | None | Testing results below posting triggers |
| Jul 20, 2021 | at Mildred Island | Caution | visual monitoring based advisory |
| Dec 4, 2018 | Middle River near Holt, Turner cut near Holt | NA - refer to Report Details | |
| Dec 4, 2018 | Middle River near upstream of West Undine Road | None | |
| Dec 4, 2018 | Middle River at Victoria Canal Confluence near Union Point | None | |
| Dec 4, 2018 | Middle River downstream of S Tracy Boulevard | 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.