California camping water: official advisories and what to do

Official California advisory pages

• California Harmful Algal Bloom portal (reports map) (Link checked Oct 29, 2026)
• Safe to Swim maps (California Water Boards) (Link checked Oct 29, 2026)
• Beach water quality postings and closures (data.ca.gov, downloadable data) (Link checked Oct 29, 2026)

Check the official map before swimming or collecting water. We never call a lake safe.

Campgrounds near lakes and rivers in California

• D. L. Bliss State ParkLake TahoeOfficial park pageCheck current advisories
• Emerald Bay State ParkLake TahoeOfficial park pageCheck current advisories
• Folsom Lake State Recreation AreaFolsom Lake / American RiverOfficial park pageCheck current advisories
• Clear Lake State ParkClear LakeOfficial park pageCheck current advisories
• Lake Oroville State Recreation AreaLake OrovilleOfficial park pageCheck current advisories

Links checked Oct 29, 2026.

California tips

• California posts harmful algal bloom reports on a statewide map. Check it for your lake before the trip, and again at the campground if you can.
• The state's beach postings data covers bacteria advisories and closures, mostly at coastal beaches. Updates are irregular, so read the posting date.

Water from a lake, river or stream? What to do

1. Avoid it first if you see a bloom. Green, blue-green or brown scum, “pea soup” or spilled-paint water means stay out and don't drink, cook with or filter it, and keep pets out. Minnesota Dept. of Health says backcountry treatment devices can't remove algae toxins, and that boiling won't remove them and can even raise toxin levels. Find another source.
2. Filter. If the water is cloudy, let it settle and then filter it. Filtering removes many germs but not dissolved chemicals or toxins.
3. Boil or disinfect. CDC says boiling is the best way to kill germs: a rolling boil for 1 minute, or 3 minutes above 6,500 feet. The next best option is to filter and then disinfect. Follow the product label. See also EPA's emergency disinfection steps. Boiling and disinfecting don't make water with chemicals or toxins drinkable.
4. Test when you can. A home kit or a certified lab can check things like bacteria and nitrate, which is useful for a cabin well or a spring you use often. Test strips can't detect algae toxins, so a “clean” strip result doesn't mean a bloom is harmless.

No advisory doesn't mean no bloom. Oregon's health authority warns: “A waterbody with no recreational health advisory does not mean that a bloom is not present” (OHA). Check the official map before swimming or collecting water. When in doubt, stay out. More on blooms: EPA harmful algal blooms.