Lagoon Monitoring

Daily and Weekly monitoring of the San Gregorio lagoon began in October 2010 as part of our grant from the Environmental Protection Agency.  Monitors are noting both the condition of the sandbar (open, closed, about to breach etc.) as well as water quality parameters at three locations in the lagoon.

In a natural, healthy state, the lagoon is an important interface between the ocean and the fresh waters of the San Gregorio creek. Fresh and salt water mingle in different ways throughout the season, allowing species like Coho, Steelhead and Tidewater Goby to prepare for their hopefully successful spawning.

When the lagoon is artificially breached, whether on purpose or by accident, an entire season of spawning can be comprised in just a few minutes.  The public can be a great help in preventing artificial breaching by being aware of the dire consequences to the fish and wildlife of unnatural opening of the sandbar.

We were fortunate to have many interested parties watching the lagoon as it swelled to incredible proportions, and were then present with a camera when the breach occurred. Within approximately 1/2 hour, the lagoon went from bay size to gentle meandering stream.

Our monitors check water quality at both half a meter from the surface, and half a meter from the bottom at three sites in the lagoon.  They also note the level at which the water column changes from fresh to salt water (stratification layer). Using a kayak, a handheld YSI meter, a camera and a data sheet, these monitors spend several hours a week collecting data in the lagoon.  This will continue throughout the year, at which point our project partners will compile and analyze the data. We will continue to share data throughout the year with our technical advisors and members of the public through our Watershed Working Group.

Please contact SGERC with any questions about our lagoon project. (650) 726-2499 or

Oct. 2010 Lagoon breach photos courtesy David & Sandra Zink