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Learn About Local Creeks

What is a watershed?

A watershed is the land area that water flows across or through on its way to a single body of water.  Typically, watershed boundaries are formed by hillsides or mountains.  The valleys between these boundaries collect precipitation and groundwater in their streams, lakes or wetlands.  The definition of a watershed is very flexible and therefore the size of a watershed can be flexible.  We tend to refer to watersheds a being nested within one another.  For instance, the Eden Canyon Watershed is part of the San Lorenzo Creek Watershed, which is part of the San Francisco Bay Watershed. 

Looking at the world this way can be a bit daunting at first when you start to realize how connected everyone is to everything else.  Our daily activities like driving to work, washing our cars, gardening, etc. influence our health, the health of our local creek, the health of our watershed and the health of the San Francisco Bay.  All downstream areas are affected by upstream actions and everyone lives downstream of someone else.  By helping to keep our watershed resources healthy, we are helping not only ourselves, but everyone else in the Bay Area. 

Check out maps for several East Bay watersheds at .

Is My Local Creek Healthy?

How can you tell if your creek is healthy without reading a lengthy report or doing extensive water chemistry testing?  There are some basic signs to look for that will tell you whether your creek is doing all right or not. 

Healthy creeks have:

  • Cool Water.  This helps reduce toxic levels of nitrates and is critical for aquatic life. 
  • Clean, clear water.  Low turbidity (less sediment or a low level of cloudiness) means higher oxygen concentrations for aquatic plants and animals.
  • A variety of pools and riffles.  Varying flow conditions add oxygen to the water and provide important habitat nooks for fish and insects. 
  • A rocky creek bed.  Cobble and gravel reduce erosion of the creek bed and provide spawning grounds for fish. 
  • Thriving native fish, amphibian and aquatic insect populations. 
  • Stable, sloping banks with abundant and diverse native vegetation.  Roots from overhanging vegetation help control erosion and provide habitat.
  • Woody debris along creek banks.  Natural debris from vegetation supports the aquatic food chain and provides habitat for fish and invertebrates. 

Unhealthy creeks have:

  • A creek bed filled with fine sediment (such as silt and sand).  Fine sediments bury aquatic insects and fish eggs, fill in pool habitat and create turbidity (cloudiness in the water)
  • Warm water or water stagnant with algae.  Algae thrive in warmer temperatures and deprive aquatic life of sunlight and oxygen.
  • Cloudy water.  High turbidity can be from algae, sediment, animal waste, chemicals or sewage.  Even yard waste (such as leaves and lawn clippings) will contribute to cloudiness and use up oxygen as it decomposes.
  • A lack or absence of fish and aquatic organisms.
  • Steep eroding banks with little or no vegetation.  With no plants to soak up runoff water and no roots to help stabilize soil, banks can erode excessively. 
  • Little or no shade from overhanging vegetation.
  • A riparian corridor with many non-native species.  Non-native species such as eucalyptus trees, periwinkle and arundo, can have a negative impact on water quality, out-compete natives and contribute to soil erosion. 
  • Yard waste, trash, tires, metal concrete rubble, or other dumped debris in the creek channel.  This debris is not only ugly to look at; it contaminates the water, reduces channel capacity and can attract pests.
  • Creek banks lined with concrete retaining walls or concrete rubble.

What can healthy creeks do for us?

Health creeks have healthy riparian corridors.  A riparian corridor is the vegetated area adjacent to and including the creek.  Healthy riparian corridors benefit plants, animals, and humans by providing:

  • Water quality protection.  Riparian vegetation prevents the sediments and nutrients in surface runoff from entering creeks.  Roots and surface litter can serve as an effective filter to protect water quality by removing much of the nitrogen and other potential pollutants dissolved in surface and ground water before it reaches the creek.  Roots can also help prevent soil erosion by holding sediment in place.
  • Flood control.  Riparian corridors and floodplains act as a sponge by absorbing floodwaters.  The water is then slowly released over a period of time, keeping creeks flowing into the late summer months.  Trees and shrubs help reduce the loss of land into creeks during flooding.
  • Water temperature.  Trees and shrubs also provide a canopy, which shades the water.  Lower water temperatures are necessary for a diversity of aquatic life.
  • A home for wildlife.  Riparian corridors are among the most productive wildlife habitats, providing dense vegetation and a high diversity of plant species.  Fish, insects, water fowl and terrestrial species rely on the food and shelter found here.
  • Natural beauty.  The abundant vegetation and wildlife in health creek habitats provide exceptional opportunities to enjoy natural beauty through recreation. 
  • Many other benefits.  Creeks are a cornerstone of California’s natural heritage.  Their healthy, functioning riparian areas provide natural beauty and enhance property values.  The economic value of these benefits is not always recognized and appreciated.  Healthy streams and riparian areas are naturally resilient, which allow recovery from natural disturbances such as flooding or drought.  A degraded creek and riparian system are unable to recover as quickly, if at all, from natural or human-caused disturbances.