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#SummerScienceFridays | What's In Our Watershed: Sources of Pollution

Here in the Los Angeles River Watershed, we have trails that lead to beautiful pools of water, the LA River to kayak in, lakes for fishing, and open spaces to explore. We encourage everyone to get outside and recreate, but it’s important to be aware that almost everything we do, from growing a garden to swimming in our waters, has the potential to pollute our watershed. By creating awareness, we can work together to reduce bacteria, trash, and other pollution that can be harmful to both human and aquatic life in and along the LA River.

What type of pollution occurs in our watershed?

There are two types of pollution: point source and nonpoint source pollution. Point source pollution comes from an easily identifiable source. One common point source is municipal wastewater treatment plants, where wastewater can be discharged into a waterway from a specific point. In contrast, nonpoint source pollution where pollutants come from a larger area and the source is not easily identifiable. A common example of nonpoint source pollution is urban runoff. LA is characterized as a heavily urbanized city, concrete sidewalks, traffic, and lots of people. With these city streets, brings oil from car engines, dog waste, trash, and other chemicals used from cleaners and fertilizers in our households. This stormwater runoff is then washed into storm drains, rivers, streams, where it eventually washes into the ocean. This water can contain nutrients, bacteria, and other contaminants that are harmful to both humans and organisms in and along our waterways and coasts.

What’s blooming in the water?

You may have heard that pollution releases large volumes of nutrients into the water, which is a common consequence from both point and nonpoint source pollution. You’re probably thinking, “Well, why are nutrients a bad thing? Don’t plants and animals need nutrients to grow?” Eutrophication is the process by which too many nutrients, particularly nitrogen and phosphorus, are added to bodies of water. Nitrogen and phosphorus are main ingredients in fertilizers and pesticides that we use to grow food and take care of our lawns, and they can also be found in human and pet waste. In high concentrations, these nutrients act like fertilizers in our waters, and cause excess algae to grow, also known as algal blooms. While this bloom can create something visually beautiful called bioluminescence, they can be very harmful. Eutrophication lowers oxygen levels in the water and when all the algae that amassed die and decay in the water, they consume and deplete all the oxygen. This can be detrimental for aquatic species that need oxygen to survive, like fish, crabs, oysters, and plants.

Healthy Watersheds

Pollution can also cause humans to be sick. E. coli is a type of bacteria found in the digestive systems of humans and animals. High concentrations of E. coli in the environment can be extremely dangerous to your health if consumed and indicate to us the presence of dangerous diseases like salmonella and giardia (4). Since E. coli enters the environment through fecal matter, one of the simplest ways to reduce the amount of E. coli entering our waterways is to make sure pet waste, diapers, and toilet paper are disposed of properly in an appropriate receptacle far away from water bodies. Proper disposal reduces the amount of E. coli that gets washed into the watershed when it rains. Another way to reduce E. coli is to be aware of which outdoor sites and trails have restrooms and to take proper care and precautions before visiting.

Get Involved!

You and your class can join efforts around the watershed to monitor the water quality of our waterways! Check them out!


Sources Cited

  1. 2018 State of the LA River Watershed Report, Council for Watershed Health

  2. Los Angeles River Quality webpage, LA Sanitation & Environment

  3. Los Angeles River Recreation Zone website, Mountains Recreation and Conservation Authority

  4. Health Implications of Escherichia Coli (E. Coli) In Recreational and Drinking Water, The Water Project

Remember to tag us in your photos this summer with #WatershedActive and stay connected with us!

Instagram- @watershedhealth

Facebook- @CouncilforWatershedHealth


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Many thanks to our #SummerScienceFriday partner for making this #SummerScienceFriday season possible!

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