Freshwater Recreation

Safe Practices for Swimming at Rivers, Lakes, and Streams


It is important to know that our rivers, lakes and streams are an open resource for the public, animals and wildlife. These water sources are considered non-potable (not safe to drink) because of their inherent risk contamination from potentially harmful organisms such as Blue-Green algae and E. coli (a bacteria in the waste of animals/birds/humans).  Under the right conditions, these organisms or the toxins they produce can make people and animals sick if ingested or absorbed through open cuts or wounds. 

It is recommended that everyone visiting rivers, lakes or streams practice these general safe and healthy habits for swimming:
  • Avoid areas that have algae or discolored water
  • Individuals who are immunocompromised should avoid contact with the water
  • Wash hands and shower after swimming or playing in the water
  • Do not drink or cook with the water
  • Do not swim if you are sick or have open cuts or wounds
  • Do not enter the water for several days after a significant rainstorm
  • Do not swim near any pipes that are draining water into the area

Swimmer's Itch:

Swimmer’s itch is a skin irritation you can get from wading, swimming, or floating in water that contains small parasites called blood flukes.  These parasites infest various birds and small animals and may be present the water. Symptoms of swimmer’s itch include an itching or stinging sensation during first contact with the skin that may last for about an hour. A skin eruption similar to an insect bite with a reddish rash may also appear. In sensitive people, intense itching and small blisters may appear. Symptoms usually lessen after a week. If you get symptoms of swimmer’s itch, over-the-counter treatments may provide relief from itching. Call your doctor if symptoms persist

 To Avoid Swimmer’s Itch:

  1. Do not swim in areas with large numbers of ducks or geese, since they carry the swimmer’s itch parasite.
  2. Swim in deep, open areas, as swimmer’s itch is more likely to occur in shallow, still waters with weeds and snails. Young children sitting along the shoreline are especially at risk.
  3. Swim for short periods of time (i.e. less than ten minutes), and rub the skin with a rough towel after getting out of the water to remove parasites before they can enter the skin.

Dams, Reservoirs, and Other Waterways 

Many Northern California waterways are part of a vast hydropower system, with dams located upstream and downstream of the most popular recreational areas. During certain times of the year, sudden changes can occur in water levels and river flows. Heavy rains, melting snow or electric generator use can change a waterway from a slow stream to a raging river in minutes. PG&E offers the following tips to protect yourself and your family in these areas:

  • Always be alert and aware of your surroundings. Dams hidden from view can still affect the water in unexpected ways.
  • Look for water level changes, including those affected by rain and melting snow.
  • Be aware of your location when powerhouses are nearby or across a stream.
  • Remember that some roads and trails might not be accessible after a water release. The extra water can flood these areas temporarily.
  • Learn the meanings of powerhouse warning signs, strobe lights and sirens. Move to a safe area when warned.

Additional water safety tips can be found here.

Additional Resources:

State of California- Blue Green Algae and Harmful Algal Blooms Monitoring Program- https://mywaterquality.ca.gov/habs/index.html

State of California- Report Harmful Algal Blooms here: https://mywaterquality.ca.gov/habs/index.html

Leeches- Leech Question and Answers Sheet (PDF)