Town data Environment

Harmful algal bloom reports, Butte County

55 algal-bloom reports in Butte County since 2016. 12 reported in 2026.

Every freshwater harmful-algal-bloom report the State Water Boards have logged in Butte County, with the advisory level (caution, warning or danger) recommended for people and pets.

Up to dateUpdated (3 h ago)Refreshed daily (the state republishes daily)Source

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55algal-bloom reports in Butte County since 2016
12reported in 2026
Lake Orovillemost often reported (23 reports)
2026-10-14latest report: Big Chico Creek

The records

ObservedWater bodyLocationAdvisoryTypeCase
Oct 14, 2026Big Chico Creek~1.1km below Ponderosa Way (509BCMCPD)None—Open
Oct 14, 2026Big Chico Creek Forest Ranch(509BCCFRx)None—Open
Sep 9, 2026Lake Orovillemiddle fork upstream of Bean CreekNone—Ongoing
Sep 8, 2026Feather RiverWest Branch at West Branch Campground (518WBF511)None—Open
Sep 5, 2026Lake OrovilleLoafer Creek Campground — Site 65 (coordinates : 39.6152051,-121.4810537) near boat dock and waterfallNA - refer to Report Details—Open
Jun 4, 2026Butte Creek~1.5mi above Willow Cr. (521BTC303)None—Open
Jun 3, 2026Fish Creek above West Branch Fish Creek (518FSH490)None—Open
Apr 28, 2026North Table Mountain Ecological ReserveNTMER 4.5Algal mat alert sign—Open
Apr 6, 2026North Table Mountain Ecological ReserveNTMER1Algal mat alert sign—Open
Apr 6, 2026North Table Mountain Ecological ReserveNTMER6Algal mat general awareness sign—Open
Apr 6, 2026North Table Mountain Ecological ReserveNTMER5Algal mat general awareness sign—Open
Apr 6, 2026North Table Mountain Ecological ReserveNTMER3Algal mat general awareness sign—Open
Oct 28, 2025Horseshoe LakeChico Rod and Gun ClubCaution—Open
Aug 29, 2025Lake OrovilleNorth ForkCaution—Open
Aug 28, 2025Private PondPrivate Farm Pond near Lone Tree RdNone—Closed
Jul 8, 2025North Table Mountain Ecological ReserveNTMER7Algal mat general awareness sign—Open
Jul 8, 2025North Table Mountain Ecological ReserveNTMER9Algal mat general awareness sign—Open
Jul 8, 2025North Table Mountain Ecological ReserveNTMER8Algal mat general awareness sign—Open
Jun 30, 2025Lake OrovilleFeathers falls /middle forkNone—Open
May 20, 2025North Table Mountain Ecological ReserveNTMER2Algal mat general awareness sign—Open
May 20, 2025North Table Mountain Ecological ReserveNTMER4Algal mat general awareness sign—Open
Jul 13, 2024Lake OrovilleLoafer Creek Recreation AreaNone—Open
Jul 7, 2024Big Chico Creek5 mile parkCaution—Open
May 22, 2023Lake OrovilleLoafer Creek Swim BeachNoneLakeOngoing
Apr 26, 2023Phantom Falls creekPhantom Falls in North Table Mountain Ecological Reserve, Gold RunAlgal mat alert sign—Open
Aug 16, 2022Lake OrovilleSouth forkNone—Ongoing
May 24, 2022Thermalito Forebayswim beachNone—Ongoing
May 24, 2022Thermalito Afterbayswim beachNone—Ongoing
Apr 26, 2022Lake Orovillenear damNoneLakeOngoing
Jun 16, 2021Butte Creek~1.5mi above Willow Cr.NoneWadeable streamClosed
May 29, 2021Thermalito forebayin OrovilleNA - refer to Report Details—Closed
May 25, 2021Dry Creekat ParadiseNoneWadeable streamClosed
May 24, 2021Concow Creekabove Camelot Ln.NoneWadeable streamClosed
May 11, 2021Clear Creekat ParadiseNoneWadeable streamClosed
May 4, 2021Thermalito AfterbaySwim BeachNone—Closed
May 4, 2021Lake Orovillenear damNoneReservoirClosed
May 4, 2021Thermalito ForebaySwim BeachNone—Closed
Jul 29, 2020Lake OrovilleLake Oroville, West BranchNoneReservoirClosed
Jun 29, 2020Lake OrovilleLake Oroville, North ForkNoneReservoirClosed
May 11, 2020Thermalito AfterbayThermalito Afterbay Swim BeachNone—Closed
May 11, 2020Thermalito ForebayThermalito Forebay Swim BeachNone—Closed
May 11, 2020Lake OrovilleLake Oroville, near damNoneReservoirClosed
Sep 13, 2019Lake OrovilleLake OrovilleNoneReservoirClosed
Jun 24, 2019Lake OrovilleLake Oroville North ForkNoneReservoirClosed
Jun 15, 2019Horseshoe LakePier near Chico Community ParkNoneReservoirClosed
Jun 12, 2019Lake OrovilleLake Oroville Middle ForkNoneReservoirClosed
May 29, 2019Lake OrovilleLake Oroville Loafer Creek Swim BeachNoneReservoirClosed
May 29, 2019Lake OrovilleLake Oroville Thermalito Afterbay Swim BeachNoneReservoirClosed
May 29, 2019Lake OrovilleLake Oroville Thermalito Forebay Swim BeachNoneReservoirClosed
May 22, 2019Lake OrovilleLake Oroville near damNoneReservoirClosed
Jul 6, 2018Lake OrovilleLake Oroville - South ForkNoneReservoirClosed
Jun 19, 2018Lake OrovilleLake Oroville - Middle ForkNoneReservoirClosed
Jun 3, 2018Lake OrovilleNorth Fork of Lake OrovilleNoneReservoirClosed
Jul 26, 2016Lake OrovilleLake OrovilleNoneReservoirClosed
Apr 24, 2016California Park LakeUpper California Park LakeDangerReservoirClosed

A report is a sighting or sample, not proof the water is still unsafe. Check the state's map for the current advisory before swimming or letting dogs in.