Tomales Bay Watershed
Tomales Bay and its watershed are a resource-rich part of Marin County. Tomales Bay is included in the Gulf of the Faralones National Marine Sanctuary. It is also part of the Central California Coastal Biosphere Reserve and the Western Hemisphere Shorebird Reserve Network (TBWC 2003 1). In 2002, the U.S. Fish and Wildlife Service (USFWS) designated Tomales Bay as a Wetland of International Importance (TBWC 2003). The National Audubon Society has recognized the Bay as an “Important Bird Area.”
The Tomales Bay watershed has intertidal, subtidal, and benthic habitats as well as dunes, mud flats, salt marshes, and freshwater marshes (TBWC 2003). Large eelgrass beds grow in the northern half of the Bay with smaller ones lining the eastern shore. Small islands provide roosts for birds and haul out areas for marine mammals. Tomales Bay subwatersheds include Inverness, Lagunitas Creek, Walker Creek, and east shore drainages such as Millerton Gulch, Grand Canyon, and Tomasini Canyon.
The Inverness subwatershed is a collection of many small creeks draining into the west shore of Tomales Bay. These creeks include Haggerty Gulch, Fish Hatchery Creek, Redwood Creek, and First, Second, and Third Valley Creeks.
The Lagunitas Creek subwatershed is the largest drainage into Tomales Bay. Its major tributaries include San Geronimo Creek, Devils Gulch, Cheda Creek, Nicasio Creek, and Olema Creek. At the southwestern edge of the watershed, Olema Creek flows in nearly a straight line through a rift valley along the San Andreas Fault zone. The subwatershed includes the Kent, Alpine, Bon Tempe, Lagunitas, and Nicasio reservoirs. The San Geronimo Valley is the last un-dammed headwaters of Lagunitas Creek, and is considered critical Coho salmon spawning and juvenile rearing habitat. In response to concerns about the effects of further development in the watershed on Coho salmon populations, Marin County DPW has prepared a draft San Geronimo Valley Salmon Enhancement Plan.
Topography in the 76-square mile Walker Creek watershed ranges from 1,500 feet to sea level where the creek empties into Tomales Bay just south of its mouth. The northern tributaries, Keyes Creek and Chileno Creek, flow through wide valleys with gentle, grassy hills. The upper watershed is much more rugged with extensive areas of coast live oak forest. The watershed contains a 220-acre natural lake, Laguna Lake, at the top of Chileno Valley. Soulajule Reservoir, constructed in 1968 in Arroyo Sausal and enlarged in 1980, is managed by the Marin Municipal Water District (MMWD).
The small tributaries draining the east side of Tomales Bay include Millerton Gulch, Grand Canyon, Tomasini Canyon, and other unnamed tributaries. These small watersheds occur on both public and private lands.
1 Tomales Bay Watershed Stewardship Plan.
Point Reyes and the Tomales Bay area have been home to Coast Miwok Indians for at least 5,000 years. Point Reyes National Seashore has over 120 known village sites (NPS 2008 1). Coast Miwok management of the landscape through burning, weeding, pruning and harvesting most likely helped to create the coastal prairie that began luring early ranchers following the Gold Rush (NPS 2008).
Since European settlement, the watershed has been used for food production. Marin County was a primary source of beef and butter for early San Francisco—beginning in 1857, the Shafter and Howard families developed a network of dairies to supply butter and cheese to the burgeoning San Francisco population. Potatoes, barley, and other grains were also grown in the watershed. From the 1850s into the early 1870s, potatoes were loaded onto shallow barges in Keyes Creek immediately downstream of the present Highway One bridge (UCCE 1995 1). The current small size of the channel at this location, more suitable for a canoe than a barge, is evidence of a significant watershed change over the past 150 years.
Mercury was mined at three sites in the Walker Creek watershed after World War II. The largest mine, at the Gambonini Ranch near the confluence of Salmon Creek and mainstem Walker Creek, closed in 1970.
Changes to Watershed Processes
The granite-derived soils in the Inverness subwatershed are very permeable, yet highly erosive and conducive to landslides and debris flows when saturated. Roads and development in the upper watersheds have led to destabilization of the hill slopes and the formation of slumps and landslides during large rainfall events. The 1982 and 1983 storm events caused many road failures and landslides, which resulted in scour of the upper channels and deposition of large amounts of sediment in the downstream, low-gradient reaches (Andrew and Willard 1983 1). The low channel gradients and influence of tidal conditions in these areas limits the amount of sediment that can be transported out to the Bay.
Portions of Keyes Creek immediately downstream of the present Highway One bridge (UCCE 1995 2) were once navigable. The current small size of the channel at this location, more suitable for a canoe than a barge, is dramatic evidence of significant change in the Walker Creek watershed over the past 150 years. Historic sedimentation has been linked to the disturbance of the native grassland through cultivation, change in species composition as introduced annual grasses gained dominance, and concentrated livestock use (Zumwalt 1972, Prunuske Chatham, Inc., 2005).
After World War II, mercury was mined at three sites in the Walker Creek watershed. The largest mine, at the Gambonini Ranch near the confluence of Salmon Creek and mainstem Walker Creek, closed in 1970. A severe storm in January 1982 destabilized the mine site and sent massive amounts of mercury-laden sediment into Walker Creek. The federal EPA, working with the San Francisco Bay Regional Water Quality Control Board (SFBRWQCB), completed remediation of the site in 2000.
The Inverness subwatershed and surrounding habitats are one of the most biologically diverse and ecologically significant areas on the California coast. Despite scattered residential and commercial development in the subwatershed, it still supports a diverse mix of well-connected upland and aquatic habitats. It also includes portions of the Point Reyes National Seashore (PORE), Tomales Bay State Park, and Tomales Bay proper.
The upper Lagunitas Creek watershed is steep and fairly heavily forested. Parts of San Geronimo Creek, Olema Creek, and mainstem Lagunitas Creek through Samuel P. Taylor State Park have areas of dense redwood growth and cool water year-round. These reaches provide spawning and rearing habitat for salmonids. Except for a few open areas, most of Lagunitas Creek downstream of the state park is thickly forested with willows and alders. The valley opens below Tocaloma Bridge to broader, more gently sloping hills that are primarily used for livestock grazing.
The Walker Creek subwatershed is a mosaic of grassland, mostly annual but grading towards perennial near the coast, valley foothill riparian forest, coastal scrub, and oak bay woodland. A small stand of redwood trees is growing in the upper reaches of the Arroyo Sausal drainage. Laguna Lake in Chileno Valley is a shallow natural lake. Officially classified as a vernal pool, it retains water year round although it diminishes significantly in area during the summer. The lake is used extensively for migrating and breeding waterfowl. Wetlands at the mouth of Walker Creek are also important habitat for waterfowl.
Mainstem Walker Creek contains areas of thick riparian forest, some of which are contiguous to upland forest. Other areas, particularly near Chileno and Keyes Creeks, have little mature riparian forest remaining, although there are ongoing efforts to re-establish native riparian vegetation.
The eastern shore of Tomales Bay is largely grassland with isolated patches of oak-bay woodland, coastal scrub, and eucalyptus. Fresh and saltwater marshes line Tomales Bay. Scattered stands of coastal terrace prairie are found within the tributaries along the east shore.
Fish and Wildlife
Tomales Bay and its watershed support over 900 species of plants and animals, including many that are listed as threatened or endangered or are identified as species of concern by state and federal agencies. Among the special-status species found immediately in and around the Bay are saltmarsh common yellowthroat, great blue heron, great egret, California black rail, Coho salmon, chinook salmon, steelhead trout, California brown pelican, Steller sea lion, and California least tern.
Approximately 45% of all bird species in North America have been recorded in the adjacent Point Reyes peninsula, while as many as 50,000 waterbirds may depend on Tomales Bay during winter (Kelly & Tappen 1998 3). Approximately 300-600 harbor seals live in Tomales Bay. According to the USDA, Gray whales forage at the mouth of the bay and at times enter the Bay. Pacific herring runs support a small commercial fishery. Tomales Bay has the second largest mariculture industry in the state.
The Inverness subwatershed’s lower baylands are prime habitat for many species including birds, marine mammals, invertebrates, and fishes. Seals and sea lions use the shores for foraging and as haul-out sites. Huge numbers of birds, including 20,000 wintering shorebirds and up to 25,000 waterbirds, utilize the shores both year-round and during migration. There are reported occurrences of federally listed as threatened and California Species of Special Concern California red-legged frog and California Species of Special Concern northwestern pond turtle within the watershed.
In addition, the Inverness subwatershed potentially supports over 50 species of mammals (ARA 2002 4; Carmen 2002b). These include the Point Reyes jumping mouse, Point Reyes Mountain beaver, both California Species of Special Concern. Southwestern river otter burrows have been observed along Fish Hatchery Creek, also a California Species of Special Concern, along with several listed bat species (ARA 2002).
In the Lagunitas subwatershed there is still a significant population of wild Coho salmon, with some estimates ranging as high as 10% of the population for the Central California Coast Evolutionarily Significant Unit (ESU). Northern spotted owl territories identified along Lagunitas Creek. Steelhead trout, California freshwater shrimp, foothill yellow-legged frogs, and California-red legged frog have also been observed in the subwatershed.
Chinook and chum salmon were observed in Lagunitas Creek during the 2001/02 and 2002/03 winters. Pacific lampreys spawn in Lagunitas Creek. Until the early 1980s,green sturgeonused the lower reaches. Mountain lions are frequently seen in the watershed and river otters have been sighted in the mainstem of Lagunitas Creek. An osprey colony has been documented at Kent Lake since the 1960s, with approximately 25-50 occupied osprey nests observed annually since 1994; bald eagles have also been sighted in recent years (Evens 2008 5).
Walker Creek grasslands are excellent places to find raptors including Swainson’s hawks, ferruginous hawks, and golden eagles. Restored riparian corridors in Chileno Valley attract a variety of neotropical songbirds species, including warblers, vireos, flycatchers, and thrushes.
Human Habitation, Land Use, and Resource Conservation
Land Use Imperviousness
The Tomales Bay Watershed Council (TBWC) was formed in 2000 with 24 members representing residential and community groups, agricultural interests, environmental groups, maricultural interests, recreational interests, and public agencies. The Tomales Bay Watershed Stewardship Plan was completed by TBWC in 2003.
Many of the goals and tasks of the Tomales Bay Watershed Stewardship Plan have since been incorporated into an overarching document produced in 2007, the Tomales Bay Integrated Watershed Management Plan (ICWMP). The ICWMP is a coordinated effort by TBWC and four Marin County water and public utility districts (Bolinas Community Public Utility District, Inverness Public Utility District, Marin Municipal Water District, and North Marin Water District). The ICWMP aims to integrate the work of each of these agencies in order to prioritize regional projects and provide a framework for watershed planning in the region. The ICWMP was funded by a grant made available through Proposition 50, the Water Security, Clean Drinking Water, Coastal and Beach Protection Act of 2002.
In addition, a pathogen Total Maximum Daily Load (TMDL) has been established for Tomales Bay, with the primary objective of protecting water quality for recreational uses and shellfish harvesting (Regional Water Quality Control Board 2005). TMDLs for nutrients, mercury, sediment and siltation are in progress. A number of agencies and non-profits are working together to support the ranching community in meeting these new requirements. In particular, the Marin Resource Conservation District (MRCD) developed the Conserving Our Watersheds (COW) Program to assist with TMDL Implementation in Tomales Bay and Stemple Creek Watershed. Through this program, MRCD provides funding and technical support for ranchers to adopt voluntary resource conservation practices that meet the TMDL objectives.
The Inverness subwatershed is part of the West Marin Planning Area according to the 2007 Marin Countywide Plan). Desired outcomes for this Planning Area include maintaining the boundaries and character of existing villages, encouraging preservation of historic structures, keeping tourist facilities at a small scale, and avoiding large-scale development.
Over half of the Lagunitas subwatershedis in public ownership. The upper part is owned and managed by Marin Municipal Water District for water supply. Samuel P. Taylor State Park is completely within the watershed boundaries. Point Reyes National Seashore and Golden Gate National Recreation Area manage extensive holdings north and west of Samuel P. Taylor State Park and in the Olema Creek and Bear Creek subdrainages.
The Lagunitas Creek watershed holds many small rural communities —Woodacre, San Geronimo, Forest Knolls, and Lagunitas in San Geronimo Valley, as well as Nicasio, Olema, and Point Reyes Station. It has been the focus of salmonid restoration efforts for over twenty years, including the recent draft San Geronimo Valley Salmon Enhancement Plan. The National Park Service, in partnership with Audubon Canyon Ranch, has begun a program to restore more than 600 acres of wetland within the Waldo Giacomini Ranch and Olema Marsh, and to incorporate opportunities for the public to experience the restored wetlands.
Current land use in the Walker Creek subwatershed is almost exclusively agricultural, with the exception of the town of Tomales. Beef is the primary agricultural product. Few dairies are left in the watershed. One vineyard has been established in the Salmon Creek subdrainage, a small organic apple orchard has been planted in Chileno Valley, and one farm is producing organic strawberries. The Walker Creek subwatershed has been the focus of a number of studies and programs to assess and improve watershed health since the 1960s. Efforts have focused on erosion and sedimentation problems, elevated mercury levels, salmonid populations, and the impacts of water quality impairments on fisheries.
The eastern drainages of Tomales Bay are mostly on private lands agricultural and/or residential lands. Miller County Park offers boat launching facilities, and Tomales Bay State Park has facilities at Tomasini and Millerton Points and a small parcel adjacent to Cypress Grove. The California Department of Parks and Recreation operates the Marconi Conference Center. Cypress Grove is a 139-acre reserve owned and managed by the Audubon Canyon Ranch on the east shore of the Bay. PRNS owns the former site of the historic town of Hamlet.
1 Survey of Eight Streams of the Inverness Ridge, Marin County, California.
2 The Marin Coastal Watershed Enhancement Project.
3 Distribution, Abundance and Implications for Conservation of Winter Waterbirds on Tomales Bay, California.
4 Giacomini Marsh Restoration Site Special-status Animal Species: Reconnaissance and Compliance. Draft report to the National Park Service.
5 The Kent Lake Osprey Colony, 40 years of growth and stability, Mt. Tamalpais symposium presentation.