Low-Flow Monitoring

In June 2000, Sonoma Ecology Center staff initiated a low-flow monitoring program in Sonoma Valley. The purpose of our program was to evaluate whether sufficient pool and run habitat is generally available to resident fish species and young salmonids in Sonoma Valley streams. Data were collected during the dry season, when streams are at their lowest, to understand where lower limits of flow are when streams are running minimally. Records will also provide insight to future studies on base flows and groundwater in Sonoma Valley.
 
Sonoma Ecology Center staff began the study by researching California Department of Fish and Game (CDFGCalifornia Department of Fish and Game) records to help identify prime fish nursery habitat. On the basis of the CDFGCalifornia Department of Fish and Game records, anecdotal evidence, and citizen observations, we selected low-flow monitoring locations that are not only proximal to known nursery habitat but that also have concrete abutments (such as bridge piers) where staff gauges could be installed (staff gauges are ruler-like scales that extend into the stream to measure depth of water). Ten regular monitoring locations were established throughout the watershed (see Slides 6, 7, and 8 of attached MS Powerpoint presentation, 20100211_LowFlow_HY00-02, for fish-related information on site selection). Staff gauges were installed in five of the locations (after gaining approvals of Sonoma County and local landowners), and five locations were monitored without benefit of staff gauges (no appropriate locations were available).
 
SECSonoma Ecology Center is a not-for-profit organization located in the Sonoma Valley. http://sonomaecologycenter.org staff, volunteers, and interns from Sonoma State University conducted the work using a portable flowmeter and wading rod. We followed U.S. Geological Survey Protocols to take instantaneous measurements as defined by the California State Water Resources Control Board's Clean Water Team (see Protocols, below). In summer 2000, SECSonoma Ecology Center is a not-for-profit organization located in the Sonoma Valley. http://sonomaecologycenter.org's low-flow team made a minimum of three field visits to each staff gauge location. In summer 2001, work resumed with nearly weekly visits to the ten sites. Results from summer 2000 indicate a maximum of 3 cubic feet per second (cfs) and a minimum of 0.7 cfs between June and September. (One cfs approximately equals 449 gallons per minute.) Results from summer 2001 indicate flow in April at 9.34 cfs and in mid June at 1.68 cfs. California Department of Fish and Game records historically noted Sonoma Creek at 1 to 5 cfs between May and November and recommended supplemental flows of 5 cfs for improved steelhead nursery habitat (Rockwood, 1966).

SECSonoma Ecology Center is a not-for-profit organization located in the Sonoma Valley. http://sonomaecologycenter.org continued low-flow monitoring using these methods through summer 2002. Results are summarized in Tables C-3 through C-5 of Appendix C of the Limiting Factors Analysis (attached). Locations correspond to those used to monitor other parameters, as specified at http://knowledge.sonomacreek.net/monitoring. In summer 2003, advisors for the Sonoma Creek Limiting Factors Analysis recommended a shift to Dry Reach Measurements (see http://knowledge.sonomacreek.net/montype/dry-reach-measurements).

Rockwood, Kevin, 1966. A Reconnaissance Report of Proposed Water Projects in the Sonoma Creek Drainage, Sonoma County. California Department of Fish and Game. Unpublished report from CDFGCalifornia Department of Fish and Game files [also in SECSonoma Ecology Center is a not-for-profit organization located in the Sonoma Valley. http://sonomaecologycenter.org historical archives].