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Biostimulation, Cyanotoxins, and Biological Condition Provisions

The State Water Resources Control Board (State Water Board) is considering statewide water quality objectives for nutrients, other biostimulatory substances, and cyanotoxins, and a program of implementation under the Biostimulation, Cyanotoxins, and Biological Condition Provisions (Provisions). The Provisions could include statewide numeric or narrative water quality objectives and regulatory control options for point and non-point sources in California’s freshwater wadeable streams and rivers, non-wadeable streams and rivers, lakes, and reservoirs. The Provisions may also establish and implement biological condition assessment methods, scoring tools, and targets aimed at protecting the biological integrity (biointegrity) in California’s wadeable streams. The Provisions will be established as state policy for water quality control and will include a water quality control plan component.

Current Announcements

July 14, 2022 Public Workshop


June 23, 2022 – Revised Notice of Public Staff Workshop

Technical Documents & Tools

The following documents are available upon request. Please contact Jacob Iversen at


California Stream Condition Index (CSCI): The CSCI is a biological index used to score the condition of benthic macroinvertebrate communities (insects that live on stream beds) in perennial wadeable rivers and streams. The scoring process involves collecting benthic macroinvertebrate samples and entering the data into GIS and R software (commonly used software for statistical analysis). Calculations and algorithms generate a score along a spectrum of biological integrity from severely impaired conditions to pristine reference sites where there is minimal to no anthropogenic impact. For more information, visit SWAMP’s Bioassessment webpage.

  • Predictive biological indices for algae populations in diverse stream environments (Theroux et al. 2020)

Algal Stream Condition Index (ASCI): The ASCI is a biological index that works similarly to the CSCI, but is based on algal communities within the stream, rather than benthic macroinvertebrate communities.

  • Characterizing benthic macroinvertebrate and algal biological condition gradient models for California wadeable streams, USA (Paul et al. 2020)

Biological Condition Gradient (BCG): The BCG is a tool that interprets ASCI and CSCI scores and places ranges of said scores into one of six “bins” associated with a narrative description of the condition of a stream or river. The six bins and their corresponding descriptions span a gradient ranging from severely impaired to pristine conditions. Policymakers can use the narrative scores and descriptions to develop numeric or narrative water quality goals.

  • Prioritizing management goals for stream biological integrity within the developed landscape context (Beck et al. 2019)

This report addresses impacts where surface water channel modification and other factors impose constraints on in-stream conditions in developed landscapes. The report includes a statewide landscape model that estimates ranges of likely macroinvertebrate index scores typical for developed landscapes.

This report established a reference-site pool with low levels of human-associated stress and a broad coverage of environmental diversity. The reference-site pool was critical in the development of the CSCI and ASCI.

Eutrophication and Biostimulatory Conditions in Wadeable Streams

  • In progress (expected June 2022): Approach to Assessment, Prevention, and Management of Biostimulatory Impacts to California Estuaries, Enclosed Bays, and Inland Waterbodies (TR#871)

TR871 is a synthesis report of biostimulatory principles and assumptions that lead to impaired beneficial uses in all California waterbody types. The report provides generalized conceptual models of drivers of eutrophication, and ten organizing assumptions and scientific principles for policy development.  One of the assumptions and principles is that statewide indices of biological integrity (e.g., the CSCI and ASCI) can be used as assessment endpoints from which to derive ranges of biostimulatory targets.

  • In progress (expected June 2022): Scientific Bases for Assessment, Prevention, and Management of Biostimulatory Impacts in California Wadeable Streams (TR#1048)

TR1048 is a technical report that provides conceptual models of drivers of eutrophication specific to wadeable streams, a review of primary and secondary eutrophication indicators, and numeric thresholds for protecting both aquatic life and human beneficial uses.

This report describes how the bioassessment indices (CSCI and ASCI) respond to the five primary eutrophication indicators – total nitrogen, total phosphorus, percent cover, benthic chlorophyll-a, and benthic ash free dry mass.

  Link to Archived Nutrient Objective Workplans and Technical Documents

  Link to Archived Information from the Biological Integrity Plan Project

Public Meetings

Advisory Groups Information

Other Nutrient Related Efforts:

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