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

Blue-Green Algae

  • What are cyanobacteria and harmful algal blooms?
    • Cyanobacteria (also known as blue-green algae) and algae occur in freshwater and estuarine waterbodies. Algae and cyanobacteria have been around for billions of years and are natural components of ecosystems. They perform many roles that are vital to our aquatic communities, by being a food source and producing oxygen. However, when certain conditions are favorable for these organisms, algae and cyanobacteria can rapidly grow causing “blooms.”bluegreenalg
  • How do I know if there is a HAB in the water?
    • Sometimes the bloom is easily visible, forming a “scum” or discoloration on the water surface. Other times, it is less visible, floating beneath the surface or on the bottom of a water body (benthic). Blooms can appear green, blue, yellow, red, or brown. Cyanotoxins, produced by cyanobacteria, cannot be visually detected in water or tissues.  A Fact Sheet from the California Harmful Algal Blooms Portal is available to aid identification of algae and cyanobacteria.
  • What are the possible health concerns of HABs?
    • Cyanotoxins and algal toxins pose risks to the health and safety of people and pets, drinking water, and recreating in water bodies affected by blooms. They can also accumulate in fish and shellfish to levels posing threats to people and wildlife. Symptoms of HAB-related illness in people and animals are available from the Centers for Disease Control and Prevention (CDC), and by contacting the California Poison Control Center (1-800-222-1222).  More details about symptoms can be found here.
  • Can animals be affected?
    • Pets, especially dogs, are susceptible to HABs because they swallow more water while swimming and playing in the water. They are also less deterred by green, smelly water that may contain HABs. Animals can experience symptoms within minutes of exposure to the toxins. These symptoms include vomiting, diarrhea, weakness, difficulty breathing, and seizures. In the worst cases, animals have died. If your pet experiences these symptoms after exposure, contact your veterinarian immediately.
  • What can I do?

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.



  • I’ve heard leeches have been found in some Plumas County lakes and ponds. Should I be concerned? 
    • Leeches are native residents in our local lakes. They are a common food for fish and waterfowl, and an important part of the natural food web in our local area. 
  • Can leeches harm me or my children?
    • While certainly unpleasant, leeches in our region are not known to transmit human diseases, and are generally not a public health concern. Be careful removing leeches from skin. If their mouth-parts are left in the skin, they may cause irritation or infection. 
  • Where do leeches typically live? 
    • Leeches are typically found in shallow, protected water, among aquatic plants or under stones, logs and other debris. Shallow areas along the edge of the lakes and ponds are an idea habitat. 
  • What is the best way to avoid leeches in natural swimming areas?
    • Summertime means more leeches. Leeches prefer the shallow, protected areas of lakes. Swimming in deeper waters and in areas free of plants and debris will reduce the likelihood of a leech finding you. 
  • What should I do after removing a leech that has attached to my skin? 
    • Be sure to clean, disinfect and bandage leech bites to prevent infection as you would any other cut. A leech bite may ooze for several hours after the leech is removed. This is caused by compounds present in leech saliva that prevent blood from clotting. There may also be irritation or itching after a bite, similar to the allergic reaction some people have to mosquito bites. If the wound doesn’t heal properly, contact your healthcare provider. 
  • Can we treat for leeches in natural swimming areas? 
    • There is no practical way to control leeches in natural waters. Chemical control measures that would reduce leech populations will also harm other beneficial aquatic animals including fish. Because leeches like to conceal themselves under sticks, stones and other debris, swimming in areas free of such material is the best way to help reduce human/leech encounters.

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 riverin 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-

PG&E- Hydropower and Water Safety Tips-