Adopt Our Watershed

Adopt Our Watershed is a simple way for YOU to help us keep our finger on the pulse of this watershed to assess its health.  This program facilitates the participation of individuals, groups, and agencies for the important mission of providing comprehensive, year-round water quality information to resource managers and to the public.

This program helps fund the continuation of the Tomales Bay Watershed Water Quality Monitoring Program which provides long-term water quality trends for sites in tributary creeks flowing through the watershed lands and in Tomales Bay. Since 2007, the Tomales Bay Watershed Council Foundation (TBWCF) has been monitoring the water quality at eleven tributary sites and four bay sites on a year-round basis (weekly wet-season and twice-monthly dry season samples). These efforts will continue, with your support. Please consider the importance of healthy waters for Tomales Bay and all of us that enjoy and depend upon this incredible resource.

The Water Quality Problem

Tomales Bay, and its major tributaries of Lagunitas and Walker Creeks are listed by the U.S. Environmental Protection Agency as impaired for pathogens, nutrients and sediment. These impairments have a significant impact on the health of the watershed, the sensitive species it supports, on public health and on the regulations facing our watershed communities. The TBWCF is the only organization monitoring the long-term trends of these water quality impairments on a comprehensive, year-round basis. The data that we have collected is used by our partners to focus resource management efforts.

The Adopt Our Watershed Program enables those concerned about the health of the waters of the Tomales Bay watershed to directly adopt a sub-watershed by sponsoring continued sampling on a year-

by-year basis. Sponsorship levels provide funding for a year of monthly sampling of each site for all impairment measurements.

Once all sites are covered for a year of monthly samples, additional sponsorships will allow for increased sampling frequency, which is important for assessing the true quality of our waters under a range of conditions.

Seasons, and especially rainfall, have a direct effect on water quality in our watershed, with storms bringing peak levels of pollutants through the system. As a result, the frequency of monitoring and our ability to collect from year to year as weather varies is imperative to our long-term understanding of trends in the Tomales Bay watershed. Our monitoring since 2007 has included weekly sampling during the wet season, and twice-monthly during the dry season.


Your sponsorship of a site enables once-monthly water quality sampleing at that site or one year for measurements of all water quality impairments. The existing program includes the analysis of pathogens (Total and Fecal Coliform Bacteria); nutrients (Nitrate, Total Kjeldahl Nitrogen – including organic nitrogen and ammonia); and sediment (turbidity), as well as field measurements of discharge rate, water temperature, salinity, dissolved oxygen and pH.

Sponsorship Levels

Watershed Sponsor: $2,000

Directly support 100% of the annual cost of sampling once per month at one of our fifteen sub-watershed monitoring sites.

For the partial sponsorship levels below, we will match your support with others for the same subwatershed to fully support a year’s monitoring.

Watershed Steward: $1,000

Watershed Supporter: $500

Watershed Team Sponsor: Any amount you choose, targeted to the subwatershed of your choice. Sponsor a single sample for $167. Or, gather 12 friends to sponsor a site for a year.

Donations to the TBWCF can be made electronically (through by clicking Donate Now at the top of the page, or mail a check directly to our mailing address at the bottom of the page (note which subwatershed on the memo line), or call and email us to discuss where to help.

Your support, at any level, will help us achieve complete sponsorship of this program.

Donations to TBWCF (a 501(c)3 non-profit organization) are tax-deductible.

See a description of our sites and sub-watersheds below

Monitored Sub-Watersheds

Below is a list of our water quality sites in the Tomales Bay watershed. Each site represents the water quality of a particular piece (a sub-watershed) of the larger system. Each site/subwatershed is unique in its size, its land-use, its residents and its influences.

Coastal Watersheds

First-Valley Creek

An important coastal tributary meeting the bay just north of the Inverness store, this perennial watershed receives water from fog-drip and the valleys of the Inverness Ridge, and provides drinking water for local residents.

Watershed Area: 0.79 square miles

Major Land-Uses: residential, IPUD water supply, open space

Stream type & Important Tributaries: Perennial stream

White Gulch

Flowing through “windy gap” at Pierce Point and into a picturesque cove, this intermittent stream is a west-shore reference tributary watershed with minimal human influence.

Watershed Area: 0.26 square miles

Major Land-Uses: Nat’l. Park lands, Tule Elk Preserve, hiking and horse-back riding

Stream type & Important Tributaries: Intermittent stream

Millerton Gulch

Meeting the Bay just south of Millerton Point, this intermittent stream represents small east-shore tributary watersheds with characteristic influences.

Watershed Area: 3.8 square miles

Major Land-Uses: Ranching

Stream type & Important Tributaries: Intermittent stream

East-Shoe Reference Tributary

Meeting the Bay just south of the Marconi conference center, this watershed represents small east-shore perennial watersheds with minimal human influences.

Watershed Area: 0.44 square miles

Major Land-Uses: Minimal human influence

Stream type & Important Tributaries: Perennial stream, spring-fed

Lagunitas Creek Watershed

San Geronimo Creek

At the downstream end of the San Geronimo Valley, this site represents the watershed of an important head water spawning ground of Coho and Steelhead.

Watershed Area: 9.44 square miles

Major Land-Uses: residential, open space

Stream type & Important Tributaries: Perennial stream

Mid-Lagunitas Creek

On Lagunitas Creek in Samuel P. Taylor State Park, this site represents the mid-watershed, below Kent Lake and the other drinking water reservoirs.

Watershed Area: 43 square miles

Major Land-Uses: residential, MMWD water supply, State Park, open space

Stream type / Important Tributaries: Perennial stream / Lagunitas Creek headwaters, San Geronimo Creek, Devil’s Gulch

Lower Lagunitas Creek

On Lagunitas Creek just south of Point Reyes Station, this site represents nearly all of the water from the upstream watershed, except Olema Creek, before it flows through the wetland, and into the Bay.

Watershed Area: 92.9 square miles

Major Land-Uses: ranching, residential, open space, state and federal park lands

Stream type / Important Tributaries: Perennial stream / Upper and Mid Lagunitas Creeks, Nicasio Creek, Olema Creek, Bear Valley Creek, Tomasini Creek

Olema Creek

A major tributary to Lagunitas Creek, this watershed represents the water flowing through the Olema Valley in an important Coho stream.

Watershed Area: 14.69 square miles

Major Land-Uses: ranching, federal park lands, open space

Stream type / Important Tributaries: Perennial stream / John West Fork, Quarry Gulch, Davis Boucher Creek, Randall Gulch

Tomales Bay Sites

Wetland-Bay Interface

Situated just north of the old north levee, downstream of the Giacomini wetland restoration, this site is where Lagunitas Creek meets Tomales Bay. This is our innermost Bay sampling site (see below for description of the others)

Inner Bay Site

Situated near Millerton Point, this site is heavily influenced by Lagunitas Creek, the inner coastal tributaries, and the long residence time of water in the inner part of Tomales Bay.

Mid-Bay Site

Situated in the middle of the length of Tomales Bay, this site represents the water of the Bay under the influence of both Walker and Lagunitas Creeks and the tidal exchange of the Bay itself.

Outer Bay Site

Situated near the mouth of Walker Creek, at an oyster farm lease, this site is heavily influenced by the quality of upstream runoff from Walker Creek, and the tides at the mouth of the Bay.

Walker Creek Watershed

Walker Creek Upstream

On the mainstem at Walker Creek Ranch, this site represents the upper portion of the Walker Creek watershed.

Watershed Area: 40.22 square miles

Major Land-Uses: ranching, open space

Stream type / Important Tributaries: Perennial stream – Arroyo Sausal, Salmon Creek

Walker Creek Downstream

At the highway 1 bridge over Walker Creek just south of Tomales, this site represents the mixing point of fresh water from Walker Creek and Bay waters.

Watershed Area: 70 square miles

Major Land-Uses: ranching, residential, open space

Stream type / Important Tributaries: Perennial stream / Upper Walker Creek, Chileno Creek

Keys Creek

Meeting Walker Creek just south of the Highway 1 bridge, this intermittent creek receives water flowing through the town of Tomales and from the valley along the Tomales-Petaluma Road.

Watershed Area: 4.7 square miles

Major Land-Uses: ranching, residential

Stream type / Important Tributaries: Intermittent stream