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Founded in 1947, the Pasadena Casting Club is a group of fly fishing enthusiasts dedicated to the art of angling and casting, conservation, education, catch and release philosophy, and camaraderie through Club meetings, outings and events.
HomeConservation - Water Quality Monitoring

Water Quality Monitoring - San Gabriel River and Big Tujunga Creek

Angeles National Forest

In Collaboration with Fisheries Resource Volunteer Corps

 

What we do
Monitor six sites on the San Gabriel River and two sites on Big Tujunga Creek

Physical/chemical parameters measured:

  • Temperature
  • pH
  • Dissolved oxygen
  • Turbidity
  • Electrical conductivity/total dissolved solids

Biological Indicators:

  • Benthic macroinvertebrates
  • Sampled and identified to Order or Family
  • Benthic community composition indicates water quality and suitability for trout

Data provided to Angeles National Forest for Compilation


San Gabriel River WQ Site Map
Big Tujunga WQ Site Map
Benthic Macroinvertebrates
Benthic Macroinvertebrates (BMI) are sampled with a 500 micron kik net placed in the stream. The bed upstream of the net is ditcurbed in about a 3' x 3' area by rubbing all the larger stones to dislodge organisms and then raking the bed to disturb the smaller particles. Organisms are swept into the net and counted/classified according to Order (e.g., mayflies, stoneflies, caddis flies, etc.) and sometimes to families within the orders. These classifications are tied to pollution tolerances by class developed by the EPA and used in California's Surface Water Ambient Monitoring Program (SWAMP). 
SGR WQM4
SGR WQM6
SGR WQM7
SGR WQM8
SGR WQM9
SGR WQM11
Results
Sampling is currently done quarterly at all eight sites. Results can be compared between sites or over a period of time. Sampling began in April 2025. Some example graphics of collected data are shown below. 
_EPT_EFSGRUS_20260714.png
_EPT_NFSGRUS_20260714.png
_EPT_WFSGR_20260714.png
BMIs as Indicators
One quick index that is considered indicative of high water quality and suitability for trout is a high percentage of mayflies (Ephemeroptera), stoneflies (Plecoptera), and caddis flies (Trichiptera), shortened as %EPT. 
_EPT_SGR_20260714.png
Seasonal Changes
Temperature can be a limiting factor for trout on the San Gabriel River. The chart below shows how temperature has varied over the past 15 months at the six stations (some winter data is absent due to high flows making sampling too dangerous). The dashed line indicates a threshold temperature of 20 degrees C (68 degrees F) at which trout are likely to be stressed. An August 2026 temperature snapshot showed that West Fork temperatures near the Cogswell Dam outlet were up to 12 degrees F lower than the sampling site downstream near the parking area, even in mid-morning. 
SGRTemp_042025to072026_rev.png
Volunteering - get wet
The water quality sampling is done with a relatively small crew of people. However, we can use more volunteers that are trained in the work so that we can put crews together as needed. Especially those that can identify, or are interested in learning to identify BMIs. If interested, contact Ed Wallace, e2wallace@gmail.com.