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Project: Demonstration of CRAM in the San Gabriel River Watershed

Background and Objectives

Wetland management depends on a comprehensive understanding of ecosystem condition. Unfortunately most monitoring and assessment is based on a single objective (e.g., regulatory compliance) or a single indicator (e.g., benthic macroinvertebrates). To remedy this shortcoming, the USEPA has proposed a three-level framework for wetland monitoring. Level 1 evaluates extent and distribution of wetland habitat (i.e., inventory), Level 2 assesses regional condition, and Level 3 conducts detailed or site-specific evaluation. SCCWRP and partners demonstrated this integrated assessment approach in the San Gabriel River Watershed, near Los Angeles, CA. The San Gabriel River watershed was chosen as the site for a level 1-2-3 demonstration project because of the unique combination of stakeholder and agency interests in establishing a regional watershed monitoring program.

Demonstration of CRAM within the context of a level 1-2-3 assessment of the San Gabriel River watershed focused on answering three important management questions: 1) What is the extent and distribution of wetlands and riparian habitat and how has it changed over time? 2) What is the condition of wetlands and riparian habitat? and 3) What is the condition at key areas of interest for management, compliance, etc? This objectives of the monitoring framework demonstration were to:

1) Characterize the range of riverine and associated riparian wetland conditions in the San Gabriel River watershed;
2) Demonstrate the utility of CRAM for regional ambient assessment, land-use planning, and monitoring associated with regulatory programs in California, such as the Surface Water Ambient Monitoring Program (SWAMP);
3) Provide the opportunity to develop a watershed profile for the San Gabriel River watershed; and
4) Provide opportunities to link wetland condition assessment with more traditional water-quality monitoring and bioassessment indicators, in order to provide a framework for integrated watershed assessment.

Figure 1. Map of probability-based ambient survey sites (marked by red and green circles and triangles) in the San Gabriel River watershed.


This project was conducted from 2005 to 2009.


For the Level 1 assessment, wetlands and riparian habitat were mapped using the National Wetlands Inventory, augmented with hydrogeomorphic modifiers. For Level 2, ambient condition was determined via probabilistic sampling of ambient riverine and associated riparian wetland condition at 30 randomly selected sites using the California Rapid Assessment Method (CRAM), an Index of Biotic Integrity (IBI), water chemistry, and toxicity tests. For Level 3, conditions at specific project sites were evaluated via intensive sampling using the same indicators as the Level 2 assessment. Level 3 monitoring data were collected at the same 30 sites randomly selected for the ambient assessment using CRAM, as well as other targeted locations, including key confluence points and permit-mandated sites, within the watershed. Level 3 monitoring was based on the “triad” approach and included bioassessment (and its associated suite of physical habitat measurements), aquatic toxicity, and water column chemistry. This triad of data provided better insight into conditions from a variety of perspectives, as well as an opportunity to assess linkages among observed parameters and any impacts on the instream aquatic community (Figure 2).

Figure 2. Assessment of overall stream condition based on individual indicators (left) and on combinations of indicators (right).


This project provided a multimetric evaluation of wetland extent and ambient condition, while offering a context to interpret condition at project sites and to identify priority needs for future analysis. Findings of the Level 1-2-3 San Gabriel River watershed demonstration study are as follows:

• The San Gabriel River watershed has experienced a loss of 38,500 acres (15,500 ha) of wetlands, which represents approximately 86% of total historical wetland acreage (Figure 3).

• Palustrine (freshwater) wetlands were the most impacted, with the greatest losses in the tidal fringe area.
• Current lacustrine wetlands are mostly man-made, representing a shift towards type-converted wetlands.

Figure 3. Landscape profile of SGR watershed wetlands historically (A) and in present day (B), illustrating the extreme loss of wetland acreage, particularly of freshwater wetlands in the tidal fringe.

• CRAM index score was significantly correlated with the development intensity index of the surrounding landscape.

• The CRAM scores, on a scale from 27-100, ranged from 35-91. The upper watershed, which is comprised of mostly natural streams, had the highest CRAM score. The mainstem of San Gabriel River, which is mainly channelized, had the lowest CRAM scores (approximately half the mean score of the upper watershed). The lower watershed, which is comprised of a mix of semi-natural and channelized systems, had intermediate scores that were comparable to mean values for the overall watershed.

Figure 4. Cumulative distribution function of % of CRAM Assessment Areas (stream miles) as a function of CRAM score, showing the scores of key sites of interest relative to watershed ambient condition.

• In general, there was a positive correlation between CRAM and IBI scores, indicating that biotic integrity (as indicated by the benthic macroinvertebrate community) is higher at sites with more intact wetland and riparian communities.

• Results of this demonstration project along with companion projects in the Napa River (San Francisco Bay Area) and Morro Bay (central coast) watersheds will be used to produce guidance as to how to implement integrated monitoring and assessment programs in other portions of the State. This work continued in a subsequent project: Development of a Statewide Framework for Wetland and Riparian Monitoring and Assessment.


This project is being conducted in collaboration with California State University at Northridge, the San Francisco Estuary Institute, US EPA Region IX, and numerous other partner agencies and institutions.

For more information on Demonstration of CRAM in the San Gabriel River Watershed, contact Eric Stein at (714) 755-3233.
This page was last updated on: 7/2/2014