The land area draining into Tomales Bay is nearly 20 times the
size of the Bay itself: the watershed area is 219 square miles.
The bay, sitting atop the San Andreas Fault, is 12 miles long and only
about 1-mile wide. Creeks flow into Tomales Bay from Mount Tamalpais
and Bolinas Ridge to the south, Inverness Ridge to the west,
and Walker Creek watershed to the east.
Eleven
villages lie within these natural boundaries. An estimated 11,000
people live here and 2.5 million people visit annually. Human
populations have been increasing. Our activities affect the Bay
and its watershed. Public
lands within the watershed include all of Tomales Bay State Park,
Samuel P. Taylor State Park and Inverness Public Utility District
and parts of Point Reyes National Seashore, Golden Gate National
Recreation Area and Marin Municipal Water District.
The Tomales Bay waters are part of the Gulf of the Farallones National Marine Sanctuary. Eighty percent of the watershed is used for agriculture, primarily for grazing dairy and beef cattle.
The watershed supplies water, provides recreational opportunities, and supports dairy and beef ranching, farming, agriculture, commercial fishing, and mariculture.
Tomales Bay watershed is home to rich wildlife communities, including nearly 470 species of birds. Coho salmon, steelhead trout, and red-legged frogs are important examples of threatened and endangered species that rely on habitats here.
Of the wild coho salmon remaining along the central California coast from Humboldt to Santa Cruz Counties, nearly 20 percent of the population spawns in Lagunitas and Olema Creek watersheds.
In 1992, the Regional Water Quality Control Board expanded the list of sources of "water quality impairment" for Tomales Bay to include nutrients (from manure, septic systems, etc.), pathogens, metals (mercury), and sedimentation.
Local action in response to these problems has generated statewide interest. In 2001, Tomales Bay was selected by the State Resources Agency as a pilot watershed management model for California, and in 2006, the Council received a planning grant from the State Water Resources Control Board as part of Proposition 50, the "Water Security, Clean Drinking Water, Coastal and Beach Protection Act of 2002."
With the funding, we have begun implementing our Water Quality Monitoring Plan, an effort that currently includes sampling water at three local swimming areas – Ink Wells, Samuel P. Taylor and Green Bridge. We also plan to begin source area monitoring in Third Valley Creek watershed and at Chicken Ranch Beach, both in Inverness, to gather data on "nonpoint sources" of pollution from septic systems and other human-related activities.
To read more, download the Tomales Bay Water Quality Monitoring Plan.
