Measures of the Health of Rivers and Streams - Hydro-Environmental Analysis: Freshwater Environments - page 204

TABLE 7.4
IBI Metrics for the Russian River, California

Score

Biological Metric 5 3 1 How to Use the Russian River Index of Biological Integrity

Taxa richness >35 35-26 <26 Obtain a sample of benthic macroinvertebrates following the state

standard procedures in California Stream Bioassessment
Procedure. Protocol Brief for Biological and Physical/Habitat.
Assessment in Wadeable Streams by CA Department of Fish and
Game dated 2003. There must be at least three replicate samples
collected at each monitoring location. The samples should be
processed by a professional bioassessment laboratory using the
Level 3 Taxonomic Effort. Determine the mean values for the six
listed biological metrics, compare them to the values in the
columns, and add the scores listed in the column headings. The
total score will be between a low of 6 and a high of 130.
Determine the biotic condition of the monitoring location from
the following categories:
Excellent

% Dominant taxa <15 15-39 >39

EPT taxa >18 18-12 <12

Modiied EPT Index >53 53-17 <17

Shannon diversity >2.9 2.9-2.3 <2.3

Tolerance value <3.1 3.1-4.6 >4.6

Good Fair Poor

30-24 23-18 17-12 11-6

Source: Harrington, J. and Born, M, Measuring the Health of California Streams and Rivers: A Methods Manual for Water
Resource Professionals, Citizen Monitors, and Natural Resources Students , Sustainable Land Stewardship
International Institute, Sacramento, CA, 1999 .

Under Step 1, data were collected from over 450 stream locations. In Step 2, a series of 10 pre-
liminary classes was developed based on the variability of the physical and chemical parameters
among potential least and most disturbed sites. Five site classes or bioregions were established.
The spatial distribution of the biological metric values was calculated in Step 4. The ability of the
metrics to discriminate was statistically evaluated in Step 6 through a comparison of the least and
most disturbed sites, and the best performing metrics within each site classes were standardized and
incorporated into the inal indices (Step 7), resulting in ive indices (one for each bioregion), each
with six or seven metrics, as shown in Table 7.5.
Index scores were established and then used to determine whether a site was biologically
impaired. Using the established metrics, if the site was identiied as being impaired, then additional
monitoring was implemented to determine the cause of the impairment, and to develop strategies,
such as TMDLs, to remove the impairment. A stressor identiication process was established to
identify the cases of impairment.
The IBI processes have been adapted by a wide variety of agencies to aid in determining whether
aquatic systems are biologically impaired. As of 2002 (USEPA 2002), the majority of states in the
United States either have or are developing multimetric biological indices (Figure 7.9).

7.8.3 I ndex of b IoLoGIcaL c ondItIon
The biological condition could be considered the primary indicator of the ecological quality, where
stressors indicating that quality include the physical habitat, water chemistry, land use, etc. The IBI
approach described earlier is often used as an indicator of the biological condition.
A biological condition approach was used in the National Wadeable Streams Assessment (WSA).
The WSA, as part of an assessment of the quality of the nation's waters, was designed to provide a
consistent and statistically valid assessment of wadeable streams (USEPA 2006). The assessment, a
collaborative effort with other private, state, and federal organizations, was designed to address the
following questions (USEPA 2006):