San Gabriel River Regional Monitoring Program

Multiple Lines of Evidence Approach (MLOE)

Monitoring stream condition was based on a Multiple Lines of Evidence (MLOE) approach, in which bioassessment (and its associated suite of physical habitat measurements), aquatic toxicity, and aquatic chemistry data provide a variety of metrics on ecological conditions at a site. Measuring multiple indicators of stream condition provides an opportunity to assess whether there are apparent linkages between observed levels of chemicals of concern, toxicity, and/or changes to physical habitat, with impacts on the in-stream biological community.

Complete lists of the chemical, toxicological and biological community parameters and their data quality objectives can be found in the program Quality Assurance Project Plan (QAPP) (SGRRMP, 2019).

The SGRRMP has collected and assessed aquatic chemistry, toxicity, bioassessment, and physical habitat data from over 100 randomly selected stream sites throughout the San Gabriel River watershed from 2008 to present. These sites were randomly selected so that we could make statistically valid inferences about the ambient condition of streams in the watershed. The SGRRMP Stakeholder Group incorporated this random sampling design so that it complements, coordinates, and is integrated within existing larger-scale monitoring efforts that address similar questions and concerns at the regional, state, and national levels. These include the Stormwater Monitoring Coalition's (SMC) Southern California Regional Monitoring Program, the State of California's Perennial Stream Assessment Program (PSA), and the US Environmental Protection Agency's (USEPA) Western Environmental Monitoring and Assessment Program.

Bioassessment samples for the SGRRMP are collected during dry weather (April through September) when the biological communities are well established. As a result, these samples do not represent the wet weather conditions of the streams. These programs use a Multiple Lines of Evidence (MLOE) approach, combining biological assessments with chemical, toxicological and physical habitat measurements at a site. Biological assessments use resident aquatic biota as direct indicators of the biological integrity of a waterbody and serve as the key indicator of the condition of streams in the watershed. Each of the other lines of evidence provide information about what the key stressors to the biological condition might be.

On the map to the left you can view each of these lines of evidence for the watershed as a whole and for each sub-region. For more detailed information regarding each line of evidence, use the links below.

Click on  the topics below to see how stream conditions change in each of the three major parts of the watershed based on the following parameters:
  1. Biotic Condition (CSCI)
  2. Physical Habitat Condition (CRAM)
  3. Water Quality (dissolved metals and nutrients)
  4. Aquatic Toxicity