Napa River Focus
A Friends of the Napa River Newsletter
Volume 8 - No. 2 - April 2001
Page 2 of 4, April 2001,
C. Dewberry & C. Malan
The Scientific Mind: Dr. Charley Dewberry
Intense: Jim Hench & Dave Garden
Sponsor: Peter Mennen
Stunning Results in the River:
Benthic Macroinvertebrate Project -
(by Charley Dewberry)
Thursday, March 29, 2001:
Friends of Napa River (FONR) have just completed their first year of study to devise a long-term monitoring program for the Napa River basin and the results have been very interesting. The macroinvertebrate (aquatic insects found in streams in substrate, on/under rocks, wood and leaf litter) diversity is very high, much higher than the diversity found throughout much of the Pacific Northwest. A number of rare and possibly new species have been found. Also, the range of species found at a site varied from 34 to over 90 species. This large range of species combined with other measures of the aquatic communities suggests that the monitoring program should be very robust and that it will work well to track the long-term trends in health of the Napa River watershed and also determine the effects of specific land use activities on the aquatic systems. Benthic macro invertebrates (insects found under the surface of water in streams) are very sensitive to water pollution.
In December 1998, the Institute of Fisheries Resources (1998) finished a study of the Napa River basin. One of their conclusions was that information about benthic invertebrates within the Napa River basin was non-existent. This was surprising. The use of benthic invertebrates for determining the health and integrity of aquatic systems is well accepted. For example, the Environmental Protection Agency (EPA) recognizes benthic invertebrate monitoring as a means of establishing the biological integrity of aquatic systems under the Clean Water Act (EPA 1997). In California, the California Stream Bioassessment Procedure (CSBP) is a regional adaptation of the national EPA Rapid Bioassessment Protocols. The method is a sensitive, cost-effective means of determining a stream's biological and physical integrity.
In 1999, FONR obtained a grant from the Mennen Environmental Foundation to establish a long-term biological monitoring program for the Napa River. They established a working relationship with the Napa County Resource Conservation District (RCD), organized a Scientific Oversight Panel (SOP) and hired Charley Dewberry, Ph.D., of Ecotrust, Portland Oregon, to provide technical assistance. FONR identified three objectives for the Napa River benthic invertebrate study:
To establish a benthic invertebrate monitoring program for assessing the biological/ecological condition and trends within the Napa River basin. This program is specifically aimed at tracking water quality for supporting native fish populations.
Establish a benthic invertebrate program to help identify causal relationships between land use decisions and the response of the benthic invertebrate communities in the streams.
To develop and disseminate materials for educational use within Napa County.
In the fall of 1999, samples were collected from 6 sites within the Napa watershed. In the spring of 2000, 33 samples were collected from a range of conditions throughout the watershed. All the sampling was done by two teams under the direct supervision of team leaders who were experienced in collecting these samples. The Napa RCD assisted the sampling by assigning a fish biologist and then helping under the direction of Dr. Charley Dewberry to collect approximately half of the samples. The samples were sent to a professional laboratory for identification.
The laboratory completing the identification and analysis reported that the "invertebrate richness that we encountered in many of your streams was astounding". The samples from the Napa River were also significantly different from those of the adjacent Russian River. The invertebrate richness of the Napa watershed exceeds that of the Russian River watershed. This means that the regional protocols are not applicable for the Napa watershed.
As a result, we have begun to devise the unique metrics and multimetric bioassessment index for the Napa watershed. The following metrics were included in the provisional Napa River benthic invertebrate assessment: Total taxa, EPT taxa, and Tolerance (these three are the same metrics as used in the Russian River index but the ranges of abundance are different for scoring), number of long-lived taxa, and the % composition of Plecoptera. These five metrics together provided a good provisional multimetric ioassessment index. With the addition of several years of collection, the Napa watershed multimetric bioassessment index should be very robust and provide an excellent monitoring program to track the health of the Napa River watershed and to determine the effect of specific land use activities on the aquatic systems.