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Project: Developing a Technical Foundation for Freshwater Biological Objectives

Background and Objectives

California’s streams are regulated through a variety of programs across multiple State and Federal agencies. A common element of every program is the need for assessment endpoints that can be used to gauge success or compliance. Direct measures of biological condition are increasingly preferred as assessment endpoints because they are more closely linked to the beneficial uses or functions that are the focus of protection and management. In contrast, chemistry- or toxicity-based assessment endpoints require inferences about their relationship with the ecological integrity of natural systems. Biological indicators have the added advantage of integrating condition over space and time, thus providing a more comprehensive assessment than other traditional indicators alone.

The goal of this project is to provide technical support for the State Water Resources Control Board’s (SWRCB’s) development of biologically-based thresholds, or bio-objectives, in freshwater systems. Research on biological objectives will help to ensure that the SWRCB’s upcoming policy has a firm scientific foundation. The SWRCB's bio-objectives policy will likely be used for regulatory application (e.g., NPDES permits, 303(d) listing, and remediation efforts).


This is project was initiated in 2010 with anticipated completion in 2015.


The technical aspects of this project will require several tasks:

• Quantifying reference (natural) conditions;
• Creating maps of current stream and wetland resources;
• Defining a stressor-response model to identify biological expectations for the mapped resources, which will likely require the creation, refinement, and/or calibration of different assessment tools (e.g., index of biotic integrity or IBI);
• Generating a waterbody classification scheme, where the stressor-response model (and potential thresholds for expected biological condition) is extrapolated to streams across the state;
• Conducting pilot stressor identification studies that evaluate use of available technical tools for determining specific causes of impairment when bio-objectives are not met.

Example of a conceptual stressor-response model relating a stressor (development intensity in the watershed) to the response (in-stream biological conditions) among different stream reaches

The initial part of this project will focus on California’s perennial wadeable streams and two associated biological indicators: benthic macroinvertebrates and riverine/riparian wetland rapid assessments. These two indicators have been prioritized since data for benthic invertebrates and riparian condition (using the California Rapid Assessment Method or CRAM) currently exists for much of the state. Ultimately, the project seeks to develop an approach for integrating multiple biological indicators like benthic algae and physical habitat assessment.


This study is being conducted in collaboration with the California Department of Fish and Game, US Geological Survey, Southern California Stormwater Monitoring Coalition, State Water Resources Control Board, and California Coastal Commission.

For more information on Developing a Technical Foundation for Freshwater Biological Objectives, contact Ken Schiff at (714) 755-3202 or Eric Stein at (714) 755-3233.
This page was last updated on: 6/30/2014