Synthesis Report: Integrating probability and targeted survey designs in regional stream condition assessments with examples from southern coastal California

California State Water Resources Control Board (SWRCB) | June 30th, 2010

Ambient water quality monitoring programs have traditionally relied on the use of targeted monitoring designs (in which sampling locations are assigned non-randomly) to a

Ambient water quality monitoring programs have traditionally relied on the use of targeted monitoring designs (in which sampling locations are assigned non-randomly) to assess the condition of aquatic resources. As probability-based surveys (in which site locations are assigned randomly) have become more widely adopted, there has been a growing desire to combine data from targeted sites with data from probability sites when making overall assessments of resource condition. We evaluated the potential for combining datasets and present an approach to combining data from the two types of surveys. We compiled biological, chemical and habitat data from 63 probability sites and 133 targeted monitoring sites in southern coastal California and compared the distribution of analyte values collected under the two designs. This analysis clearly demonstrates that both targeted and probabilistic sampling designs are necessary for effective non-point source water quality monitoring programs. Probability designs are the only survey type capable of giving an objective overview of the range of conditions present in the resource of interest. By contrast, targeted designs often are needed to fill in critical data gaps and answer site-specific questions. We conclude that the most effective way to ‘integrate’ probability and targeted surveys is to use probability surveys to produce an unbiased regional framework for interpreting targeted results and to supplement this framework as needed with sites targeted to fill data gaps.

Tahoe: State of the Lake Report 2025

University of California, Davis (UC Davis) | July 18th, 2025

UC Davis has conducted research at Lake Tahoe since 1950, and scientists from UC Davis Tahoe Environmental Research Center have been monitoring conditions at the lake con

UC Davis has conducted research at Lake Tahoe since 1950, and scientists from UC Davis Tahoe Environmental Research Center have been monitoring conditions at the lake continuously since 1968. This has created a unique document of change for one of the world’s most iconic and vulnerable lakes.

Technical Approach to Develop Nutrient Numeric Endpoints for California

California State Water Resources Control Board (SWRCB) | July 31st, 2006

This report provides an approach for the development of nutrient (nitrogen and phosphorus) numeric endpoints for use in the water quality programs of the California’s S

This report provides an approach for the development of nutrient (nitrogen and phosphorus) numeric endpoints for use in the water quality programs of the California’s State Water Resources Control Board (State Water Board) and Regional Water Quality Control Boards (Regional Water Boards). The approach provides a methodology to support several water quality program components including: setting numeric limits for National Pollutant Discharge Elimination System (NPDES) permits; development of Total Maximum Daily Load (TMDL) nutrient numeric endpoints; and for those Regional Water Boards that choose to, the development of numeric nutrient criteria. Guidance for this technical report comes from participants at workshop (Nutrient Numeric Endpoints Training Workshop held on May 18 & 19 2005 in Sacramento, CA) that is a part of a longer running process that has been sponsored by EPA Region IX and the State Water Board.   The workshop summary (Summary of May 18-19, 2005 Nutrient Workshop) of this workshop can be downloaded from the project website: http://rd.tetratech.com/epa/. The CA Nutrient Numeric Endpoints process includes a Regional Technical Advisory Group (RTAG); and a collaborative forum of Regional Water Boards, Tribes, and other state and federal agencies in the State Regional Technical Advisory Group (STRTAG). The result of the RTAG / STRTAG process is an approach that has achieved a high level of consensus among participants. The purpose of this document is to describe the approach that has been reviewed and approved by the STRTAG. The intention of the proposed approach is to select nutrient response indicators that can be used to evaluate risk of use impairment, rather than using pre-defined nutrient limits that may or may not result in eutrophication for a particular water body. The report provides a description of the proposed approach that includes innovative elements such as: A water body classification framework that uses three Beneficial Use risk classification categories; Risk-based secondary indicators that are more closely linked to Beneficial Use condition than water column nutrient concentrations; and Modeling tools that provide the necessary linkage analysis between secondary indicators and water column nutrient concentrations. The modeling tools also account for site-specific cofactors such as flow, light availability, and others. This report provides the starting point for a process that will lead to refinements in the classification framework, secondary indicators, and linkage analysis modeling tools through the development of site-specific endpoints. The report has been reviewed by workshop participants; other State, Federal, and Tribal staff; and the Technical Evaluation Committee identified in Appendix 1. This report includes changes made in response to comments received. As an adaptive management process technical updates will be made and new dated editions of this document will be made available. A potential outcome of this process is the adoption of the framework and endpoints by various Regional Water Quality Control Boards for use as nutrient numeric criteria.

Technical Report for the Interagency Ecological Program (IEP) Pelagic Organism Decline (POD) Workgroup: Assessment of Aquatic Herbicide Use in the Delta

San Francisco Estuary Institute (SFEI) | May 15th, 2006

Since 2001, the California Department of Boating and Waterways (DBW) has conducted an extensive water quality monitoring program in conjunction with its aquatic herbicide

Since 2001, the California Department of Boating and Waterways (DBW) has conducted an extensive water quality monitoring program in conjunction with its aquatic herbicide applications. In this report, the risk quotient calculation method utilized by the Aquatic Pesticide Monitoring Program (a USEPA Tier 1 risk assessment) was used to determine if there are patterns of Level of Concern exceedances that indicate the possibility of adverse impacts on the Delta aquatic ecosystem due to DBW aquatic herbicide applications. Level of Concern exceedances are indicative only of the need for further investigation of an application scenario and do not, in and of themselves, indicate adverse impacts. This type of risk analysis cannot quantify the potential additive or synergistic effects of all pelagic organism stressors (one of which would be aquatic herbicides) within the Delta. This risk assessment indicates that, with the exception of diquat dibromide applications, DBW herbicide applications are unlikely to have the potential to cause Delta ecosystem water quality impacts. While there were a number of Level of Concern exceedances for diquat, DBW and all regulatory agencies involved were aware of this potential prior to application. NOAA Fisheries requested that, when possible, diquat used adjacent to salmon migratory routes should be reduced or avoided when that species is likely to be present. USFWS determined that diquat impact to aquatic invertebrates is minimal, temporary, and not likely to jeopardize Delta smelt but has required avoidance in areas where and when the smelt are known to be present. For 2006, NOAA has allowed DBW to treat sites in April and May with fluridone, which has allowed the use of diquat to be discontinued.

Temporal concentrations of Quaternary ammonium compounds in wastewater treatment effluents during the COVID-19 pandemic, 2020–2021

Elsevier | November 19th, 2024

The California Stream Condition Index

California State Water Resources Control Board (SWRCB) | December 1st, 2015

The California Stream Conditon Index (CSCI) is a biological scoring tool that helps aquatc resource managers translate complex data about benthic macroinver

The California Stream Conditon Index (CSCI) is a biological scoring tool that helps aquatc resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score indicates whether, and to what degree, the ecology of a stream is altered from a healthy state. Direct measures of ecosystem health like the CSCI are preferable to those based on chemical or physical measurements for many management questons. Living organisms integrate the efects of multple stressors, such as sedimentaton, nutrient enrichment and riparian disturbance, over both space and tme.

The California Stream Condition Index (CSCI): A New Statewide Biological Scoring Tool for Assessing the Health of Freshwater Streams

California State Water Resources Control Board (SWRCB) | September 1st, 2015

California’s dramatic environmental diversity supports a broad array of natural stream types throughout the state. Bioassessment of freshwater stream and rivers is esp

California’s dramatic environmental diversity supports a broad array of natural stream types throughout the state. Bioassessment of freshwater stream and rivers is especially challenging in such a region because the reference condition, or the benchmark of biological condition expected when human disturbance in the environment is absent or minimal, varies greatly among natural stream types. Previous indices used by monitoring programs were developed on a regional basis to help partition the state’s environmental diversity, but statewide assessments were confounded by different criteria used in different regions. The CSCI, which translates complex data about individual benthic macroinvertebrates (BMIs) found living in a stream into an overall measure of stream health, was developed specifically to address some of the shortcomings of earlier indices. First, the CSCI was developed with a much larger, more representative data set that makes it applicable statewide and that covers the broad range of environmental variability among natural stream types. Second, the CSCI sets biological benchmarks for a site based on its site-specific environmental setting. Finally, the CSC combines two separate types of indices, each of which provides unique information about the biological condition of a stream: a multi-metric index (MMI) that measures ecological structure and function, and an observed-to-expected (O/E) index that measures taxonomic completeness. Together they provide multiple lines of evidence about the condition of a stream, providing greater confidence in results than a single index.

The California Stream Condition Index (CSCI): A New Statewide Biological Scoring Tool for Assessing the Health of Freshwater Streams

California State Water Resources Control Board (SWRCB) | October 19th, 2015

California’s dramatic environmental diversity supports a broad array of natural stream types throughout the state. Bioassessment of freshwater stream and rivers is espe

California’s dramatic environmental diversity supports a broad array of natural stream types throughout the state. Bioassessment of freshwater stream and rivers is especially challenging in such a region because the reference condition, or the benchmark of biological condition expected when human disturbance in the environment is absent or minimal, varies greatly among natural stream types. Previous indices used by monitoring programs were developed on a regional basis to help partition the state’s environmental diversity, but statewide assessments were confounded by different criteria used in different regions. The CSCI, which translates complex data about individual benthic macroinvertebrates (BMIs) found living in a stream into an overall measure of stream health, was developed specifically to address some of the shortcomings of earlier indices. First, the CSCI was developed with a much larger, more representative data set that makes it applicable statewide and that covers the broad range of environmental variability among natural stream types. Second, the CSCI sets biological benchmarks for a site based on its site-specific environmental setting. Finally, the CSCI combines two separate types of indices, each of which provides unique information about the biological condition of a stream: a multi-metric index (MMI) that measures ecological structure and function, and an observed-to-expected (O/E) index that measures taxonomic completeness.  Together they provide multiple lines of evidence about the condition of a stream, providing greater confidence in results than a single index.

The Development of Nutrient Criteria for Ecoregions within: California, Arizona, and Nevada

U.S. Environmental Protection Agency (EPA) | January 1st, 2002

Development of regional nutrient criteria is one component of a larger strategy to address water quality problems associated with nutrient over-enrichment and cul

Development of regional nutrient criteria is one component of a larger strategy to address water quality problems associated with nutrient over-enrichment and culturally-induced accelerated rates of eutrophication of waterbodies in the U.S. The U.S. Environmental Protection Agency (EPA) and Department of Agriculture have several active program initiatives to address the nutrient overenrichment problem. These programs address point and nonpoint sources of pollution, evaluate public health impacts from animal feeding operations, conduct research and monitoring to provide data and assessment techniques to better characterize the problem, and have offer nutrient management policies to provide practical support to agricultural operations to reduce the export of nutrients from their lands. The purpose of the regional nutrient criteria development process is to provide numeric targets for the various nutrient management programs that are regionally appropriate by reflecting geographic variations of waterbody response to nutrients. The current nutrient criteria development process for California and EPA Region IX (California, Nevada, Arizona, and Hawaii) started with the publication of the National Strategy for the Development of Regional Nutrient Criteria (EPA 1998) in June 1998.

The effects of kaolin clay on the amphipod Eohaustorius estuarius: Part Two

San Francisco Estuary Institute (SFEI) | April 3rd, 2017

A number of lines-of-evidence suggest that the amphipod Eohaustorius estuarius has variable tolerance to clay in sediments. In Phase 1 of the current RMP special study, l

A number of lines-of-evidence suggest that the amphipod Eohaustorius estuarius has variable tolerance to clay in sediments. In Phase 1 of the current RMP special study, laboratory dose-response experiments were conducted in 2014 with kaolin clay to evaluate whether clay effects varied with amphipod size. The results indicated that smaller amphipods were more tolerant of clay than larger individuals. Average survival was 81%, 79%, and 65% for small, medium and large amphipods, respectively, in concentrations > 50% clay. As part of Phase 2 confirmation studies conducted in 2015-2016, the original kaolin dose-response experiments were repeated. Results of this experiment showed that average amphipod survival was 88%, 63%, and 41% for small, medium and large amphipods, respectively, in concentrations > 50% clay. Standard 96-hour reference toxicant tests with cadmium chloride (CdCl2) were conducted to determine whether there were size-specific differences in response to this metal reference toxicant. The CdCl2 median lethal concentrations (LC50s) for small, medium and large amphipods were 6.78, 5.13, and 4.63 mg/L, respectively. Responses of all three size classes to cadmium were within historic confidence intervals for this reference metal, and were not significantly different from one another based on overlapping confidence intervals. Additional experiments with high clay reference site sediments from San Francisco Bay were conducted to confirm the size related response with field sediments. The results confirm that use of smaller amphipods in routine monitoring of high clay sediments will reduce the influence of this factor on test results.