Calleguas Creek Watershed Monitoring Project Update                                                                Updated April 2008

The volunteer-based water quality monitoring program was launched in January 2006.  Each month, project staff and volunteers collect samples at eight sites on Calleguas Creek and its tributaries - Revolon Slough, Conejo Creek, and Arroyo Simi.  With the exception of one site (which was dry for most of the year), all are tested for in-stream parameters including dissolved oxygen, pH, conductivity, and turbidity, and samples were taken for bacteria and nutrient analysis.  Additional samples have been collected for more in-depth analysis of metals and pesticides as well.  A bio-assessment has been completed by a hired expert.

It takes many years of data collection to see long-term trends in water quality.  However, while we cannot yet determine long-term trends, we can begin to make general observations about water quality at particular sites, and compare water quality between sites.

In general, the results for the in-stream parameters mentioned above are within normal ranges.  The one exception is at the lowermost site on Revolon Slough (RS1) where conductivity is often quite high.  This may be due to salt water influence, or it may be a sign of some sort of contamination.  Further testing will help us learn more.

Bacteria levels vary from site to site, but several stand out as having unhealthy levels of certain types of bacteria.  RS1 (Revolon Slough at Pacific Coast Highway ) and CJ3 (Conejo Creek at the library park) show consistently high levels of all three types of indicator bacteria (Total Coliform, E. Coli, and Enterococcus).  This likely indicates some sort of contamination by human fecal matter and other sources.  Other sites show more mixed results: for example, AS1 (Arroyo Simi at Madera Road ) shows high levels of Total Coliform and E. Coli, but low levels of Enterococcus.  This means it is less likely that the contamination is coming from human fecal matter, but may be coming from animals or other natural sources.

Nutrients have been analyzed by the University of California at Santa Barbara’s Long Term Ecological Research Program laboratory. Preliminary analysis shows that this watershed suffers from particularly high nutrient levels, especially in the lower reaches of the watershed where land use is primarily agricultural.  Nitrate levels are well above public health limits on the lower reaches of Calleguas Creek and Revolon Slough, often reaching 2-3 times the public health limit.  Phosphate and ammonium levels are also unusually high throughout much of the watershed.  Our program advisor from UCSB stated, “You are dealing with water which has some serious nutrient problems.”

We are still in the process of analyzing our metals, pesticides, and bio-assessment data.  At this time, Wishtoyo Foundation / Ventura Coastkeeper is seeking funding to continue this important watershed monitoring program.