Three key stream condition indicators integrated via index

The Southern California Stormwater Monitoring Coalition (SMC) and SCCWRP have developed a new assessment tool that synthesizes three key lines of evidence about the ecological health of wadeable streams to provide an easy-to-communicate, integrated assessment of overall stream condition.

The Stream Quality Index (SQI), published as an interactive web application in July and described in a SCCWRP technical report, addresses the long-standing management challenge of not having a scientifically robust method for synthesizing and interpreting biological, chemical and physical measures of stream condition.

Consequently, stream managers have traditionally interpreted results from each of evidence separately – a particular challenge when biological, chemical and/or physical lines of evidence present conflicting assessments of stream health.

The SQI provides stream managers with a systematic, scientifically rigorous approach to integrate biological, chemical and physical lines of evidence. Each stream site is assigned to one of four condition categories that can be readily communicated to managers and non-technical audiences.

The SQI already is being transitioned to use by California’s stream management community. The SMC is planning to use the SQI as its primary assessment tool for the SMC’s next synthesis report on the condition of wadeable streams in coastal Southern California.

The State Water Board’s Surface Water Ambient Monitoring Program (SWAMP), meanwhile, is planning to recalibrate the index for use at a statewide level, including for its next statewide synthesis report. Currently, the SQI is calibrated with data strictly from Southern California.

The SQI uses a stressor-response empirical model to describe the expected likelihood that chemical and physical stressors at a stream site will degrade its biological condition.

The SQI assigns assessed sites to one of four condition categories: “healthy and unstressed,” “healthy and resilient,” “impacted by unknown stress” and “impacted and stressed.”

The four categories are designed to provide stream managers with relevant, directly actionable insights. For example, a stream site that is “impacted and stressed” for insects and physical habitat might require different management actions than a site that is “impacted and stressed” for algae and water chemistry.

To improve access to the underlying data and analyses that go into SQI assessments, SCCWRP has developed an interactive web tool that maps SQI data by stream site. Users can click on a site, then look at the underlying data and analyses to draw inferences about potential causes of impacts and/or to prioritize the site for follow-up.

For more information, contact Dr. Marcus Beck