Water Quality Monitoring
The SPAWNERS Water Quality team meets monthly at the El Sobrante Library. We take a sample of creek water from the Appian bridge, and test it for factors that affect aquatic life. We also test the water at the mouth of the creek, and monitor native oyster populations in a project sponsored by Save the Bay. Visit www.savesfbay.org for more information about oysters and how they relate to water quality. We have been compiling water quality data for two years now, which provides a good baseline for assessing the overall health of the creek.

Water Quality Parameters tested:

Dissolved Oxygen (DO)

  • Oxygen levels greatly influence the species of fish and other aquatic organisms that can live in the creek.
  • DO drops as the water temperature increases.
  • DO sources: water turbulence, photosynthesis by green plants.
  • DO sinks: decay of organic matter (excess debris such as yard clippings, animal waste)

Water Temperature

  • Temperature affects:
    • reproduction and migration of aquatic organisms
    • metabolic rate
    • sensitivity to stress
  • Human factors influencing water temperature:
    • Removal of riparian vegetation
    • Soil erosion – suspended particles absorb heat
    • Alterations to stream morphology (shape of the channel) and flow

pH: Acidic or Basic?

  • As pH decreases, water becomes more acidic. As pH increases, water becomes more basic.
  • Most organisms thrive in a narrow range of pH, 6.5 – 8.5 (pH 7.0 is neutral, neither acidic or basic).
  • Chemical discharges to the creek can alter pH.

Turbidity: Suspended particles in the water

  • Storm water run off can increase turbidity by washing in topsoil and sediment.
  • High sediment can clog the gills of fish.
  • Settlement of sediment can foul gravel beds and smother fish egg and benthic (bottom-dwelling) insects.

Conductivity/Salinity

  • Conductivity is the ability of the water to conduct and electrical current.
  • Salinity is the amount of salts in the water.
  • Dissolved ions increase salinity as well as conductivity.
  • High conductivity can indicate a sewage leak.


How healthy is San Pablo Creek?

  • Overall health is adequate for fish species such as sticklebacks and California roach, which are relatively tolerant of high water temperatures.
  • Dissolved oxygen and temperature in the summer are near the limits of tolerance for salmonids (salmon and trout).
  • Most of the water quality factors are similar to other urban creeks, but the turbidity is higher, indicating a problem with erosion.
  • A survey in 1999 found four species of fish in the creek, Sacramento Sucker, California roach, Three-spine Stickleback, and Steelhead Trout.
Volunteers testing San Pablo Creek's water quality.