Creeks & Watersheds
Healthy Watersheds
Rushing creek
Watershed science

What is a Healthy Watershed?

A watershed is all of the land that drains to a particular stream, river, or bay. All land, from the wildest preserve to the most densely developed urban neighborhood, is part of a watershed.  When watersheds are healthy and functioning well, they provide food and fiber, clean water, and habitat for native plants and animals. Healthy watersheds work hard. They move sediment from the mountains to the beaches and bays, sorting it along the way to create diverse landscapes and habitats. They cycle nutrients and convert them into forms that living organisms can use. They purify and store water, and then meter its release into streams to reduce flooding and damaging erosion in the winter and to sustain flows and cool temperatures during the dry season. They even affect air quality by absorbing pollutants and greenhouse gases. Well-functioning watersheds are more resilient to natural and human-induced disturbances than highly-impacted watersheds.

Characteristics of a healthy watershed include:

  • Water quality is high enough to support native aquatic species. In many Marin County streams, these include steelhead trout, coho salmon, and the types of aquatic insects that provide their food.
  • The streams and their floodplains are able to accommodate flood flows without regular destructive flooding and erosion.
  • Streamflows are close to historic conditions with moderate peak flows after winter storms and stable summer baseflows. This is strongly correlated to the amount of hard, impervious surfaces such as roofs and pavements throughout the watershed, especially those that are directly connected to streams through ditches and storm drains.
  • Streams have sufficient complex habitat features including pools, gravel bars, and large pieces of wood to support fish and other aquatic wildlife even through short-term changes from drought, wildlfire, landslides, or other events that alter habitat conditions in parts of the system.
  • Native, keystone plant and animal species are able to sustain stable populations. Examples in Marin County include clapper rail, valley live oak, steelhead trout, and spotted owl.
  • The riparian corridor has a dense, healthy native plant community that regenerates naturally.
  • Upland forests and grasslands are managed to promote rain infiltration, provide diverse habitat for native wildlife, reduce soil erosion, and deliver clean water into streams.
  • Tidal areas are connected to their wetlands.

What can you do to help your watershed’s health?

  • Learn more about your watershed and its specific issues and challenges.
  • Plant native plants that fit your specific location and conditions.  When you can, plant a variety of species and types of plants from grasses for erosion control and wildflowers for bees and butterflies, to shrubs and trees for birds and healthy streams.
  • Reduce impervious surfaces and disconnect them from streams and storm drains.  Use porous alternatives such as gravel or pervious pavement for driveways and paths.  Collect roof runoff and slow its release through rain barrels, rain gardens, and bioswales. 
  • Keep water clean.  Prevent soil erosion, use non-toxic household and garden products, keep oil and animal waste out of streams and storm drains.
  • Repair erosion wherever possible with biotechnical techniques that incorporate native plants.  These methods allow for natural watershed functions to continue.
  • Protect and restore riparian areas.