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The 660-square-mile Alameda Creek Watershed is the largest watershed in the Bay Area, draining roughly the southern two-thirds of the East Bay. It extends as far south as Mount Hamilton, north to Mount Diablo, east to the Altamont Hills in Livermore, and west to San Francisco Bay. There are two major tributaries to Alameda Creek, with many smaller feeder creeks: Arroyo de la Laguna in the north and the south fork of Alameda Creek. The watershed is crossed by two major water delivery systems for the Bay Area, the Hetch Hetchy Aqueduct and the State Water Project, and includes three man-made reservoirs: Lake Del Valle, San Antonio Reservoir and Calaveras Reservoir. Flows in the upper reaches of the Alameda Creek watershed are controlled by water releases from Calaveras Reservoir, which is managed by the San Francisco Public Utilities Commission (SFPUC). Calaveras Reservoir captures natural runoff and stores imported water from the Hetch Hetchy reservoir. The local runoff in the Upper Alameda Creek Watershed is managed by Zone 7 Water Agency, while supplies for public and wildlife use come from the State Water Project. The Alameda Creek Watershed can be broken into two sections, lower and upper. The information in this watershed page focuses on the 435 square mile southern section of the Upper Alameda Creek Watershed. Much of this southern section is grazed by cattle and consists of protected public land or rural privatelands, and drains areas of Pleasanton, Livermore and Sunol. It contains the two highest peaks in the Diablo Range, Mount Hamilton at 4,230 ft. and Mount Isabel at 4,230 ft., and large open-space/wilderness areas with the 28-mile Ohlone Wilderness Trail terminating in Del Valle Regional Park. The following subwatersheds are included in this southern section of the Upper Alameda Creek Watershed:
- Arroyo Hondo
- Upper Alameda Creek
- San Antonio Creek
- Arroyo Del Valle
- Arroyo Mocho
For information on the Lower Alameda Creek Watershed, return to the Explore Watersheds homepage and download the Watershed Map of Western Alameda County, or visit the Lower Alameda Creek Watershed information page. For information on the northern section of the Upper Alameda Creek Watershed, click here.
Downloads: Overview map (PDF)
The southern section of the Upper Alameda Creek Watershed is the most rural area within the vast Alameda Creek Watershed. Characterized by broad expanses of protected space, urban development is almost entirely contained within the northern tips of the Arroyo del Valle and Arroyo Mocho subwatersheds. Creeks in this portion of the watershed flow through tens of thousands of acres of protected, undeveloped land owned and managed by public agencies such as East Bay Regional Park District and San Francisco Public Utilities Commission. They begin as small tributaries in the undeveloped hills and mountains of the Diablo Range, combining and growing in size as they enter lower elevations, eventually all merging with Alameda Creek in the Sunol Valley.
Despite the expanses of undeveloped land and free-flowing streams, the southern section of the Upper Alameda Creek Watershed has been significantly altered by human activities. As creeks flow down from the Diablo Range, most of them will eventually flow into one of three man-made reservoirs: Calaveras Reservoir, San Antonio Reservoir and Del Valle Reservoir (aka “Lake Del Valle”). These reservoirs and their associated dams are used to store water and release water to downstream areas via creeks and channels. These releases recharge groundwater stores and provide water for use in the Livermore Valley. In addition to the larger dams, smaller dams, such as the Alameda Creek Diversion Dam, have been constructed throughout the watershed to feed the large reservoirs.
Flora and Fauna
Extensive stretches of open space in the southern section of the Upper Alameda Creek Watershed support large numbers of native plants, animals and insects. In addition to vegetation communities common throughout Alameda County – grasslands, sage / scrublands, oak woodlands, and riparian forests – this portion of the watershed also supports uncommon vegetation communities, which contain a variety of special-status plants found only in the Bay Area. Big scale balsam root can be found on serpentine bunchgrass grasslands, while Hospital canyon larkspur and Mt. Hamilton thistle occur in certain freshwater seeps. The Sunol Regional Wilderness is renown for its spring wildflowers, which are celebrated every year at the Spring Wildflower Festival.
This area is home to animals not common throughout the rest of Alameda County as well. A heard of Tule elk utilize the expanses of open space in and around the Ohlone Regional Wilderness, and bald eagles have been reported nesting and hunting around Lake Del Valle, Calaveras Reservoir, and in the Sunol Regional Wilderness. Multiple special-status reptile and amphibian species, including the California tiger-salamander, California yellow– and red-legged frogs, California horned lizard and Alameda whipsnake, may be found in this section of the watershed as well. More common wildlife, such as mountain lions, bobcats, deer, gray fox, and a variety of ducks and songbirds also make their homes here.
The southern section of the upper Alameda Creek watershed once hosted runs of steelhead trout and Coho salmon, although these species can no longer access these creek reaches due to downstream barriers. Numerous non-migratory native fish, however, are still present, including the western brook lamprey, Sacramento pikeminnow and rainbow trout. Non-native species also inhabit the creeks and reservoirs of this portion of the watershed, including large- and small-mouth bass, striped bass, bullfrogs, and catfish. Many of these non-native species can be caught in Lake Del Valle.
Geology and Hydrology
The Diablo Range dominates the topography, creating large variations in elevation from just under 400 feet in valleys and lowlands to over 3,000 ft in the mountainous regions. Some peaks in this portion of the watershed, such as Mt. Hamilton, extend above 4,000 ft and are among the tallest in the Bay Area. This rugged and varying topography was largely created by the Calaveras fault, which runs from Danville to the area south of the Calaveras Reservoir. Many of these steep slopes are comprised of soil types that are prone to erosion, which can lead to increased runoff and sediment within streams in large storm events. (Learn more about the different soil types found in the watershed here.)
Hydrology in the southern section of the Upper Alameda Creek Watershed has been significantly impacted by humans. Calaveras, Turner (San Antonio Reservoir’s dam) and Del Valle dams have created the three largest bodies of water in the entirety of the Alameda Creek Watershed. Natural and seasonal variations in stream flow – common to watersheds throughout the Bay Area – are amplified by the use of waterways in this area to move water from these storage facilities to areas downstream. These releases can create exceptionally high flows during times of the year when, historically, many creeks would have very low flows or when flows would have fully retreated below ground. Despite alterations to flows in its tributaries, Alameda Creek supports sustained flows year-round and provides significant groundwater inflow along its banks.
The largest issue in this portion of the watershed is the historical damming of creeks to create large reservoirs. The reservoirs in the southern section of the Upper Alameda Creek Watershed act as huge sediment traps that prevent coarse sediment from flowing downstream as it would naturally. Coarse sediment is not only an important habitat feature for many native fish, it also helps to prevent things like channel incision and bank erosion. Channel incision and bank erosion can contribute to unnaturally high banks along creeks, cutting the creek off from its historic floodplain. The movement of water from the storage reservoirs to downstream areas also creates unnatural variations in stream flow. In some areas, work is already underway to resolve or improve these issues. Read more about these important Restoration efforts on our page.
Dams in the lower portion of the watershed create barriers for fish migration to the southern section of the Upper Alameda Creek Watershed. This portion of the watershed is not currently accessible to steelhead and other anadromous species, although this species was historically present and have been observed downstream from barriers. The dams of both the San Antonio and Calaveras Reservoirs, along with the Alameda Creek Diversion Dam, have further fragmented fish habitat in this area. There are a number of active restoration projects in the lower watershed, which you can read about here.
The following information pertains to the northern section of the Upper Alameda Creek Watershed, which includes the following subwatersheds: Arroyo de La Laguna; Alamo Canal; Arroyo Mocho Canal; Arroyo Las Positas; and Chain of Lakes. To download a printable PDF map, click on the subwatershed name.
Arroyo Hondo is a 99-square-mile subwatershed of the Alameda Creek Watershed that begins in the rugged mountains of the Diablo Range near Mount Hamilton, and flows north into Calaveras Reservoir. Most of the vast, undeveloped land in this subwatershed is managed by The San Francisco Public Utilities Commission (SFPUC) and cattle ranchers. Mount Hamilton, 4,265 ft., is the highest point in the watershed. Lick Observatory is an astronomical observatory located at the summit of Mount Hamilton. Arroyo Hondo is a northwestward-flowing creek in Santa Clara County that begins at the confluence of Smith and Isabel Creeks and flows to Calaveras Reservoir. Arroyo Hondo meets Calaveras Creek in Calaveras Reservoir, and is a main tributary to Alameda Creek. The dam at Calaveras Reservoir is being replaced by the SFPUC, and is one of the only dams built in California in the last 30 years. The dam project includes some steelhead restoration measures, including a fish ladder in the Alameda Creek Diversion. An Assessment of Fish Upstream Migration at Natural Barriers in the Upper Alameda Creek Subwatershed was conducted by the SFPUC to evaluate stream features that are potential barriers to adult steelhead immigration. The assessment provides useful information to steelhead restoration efforts and the feasibility of creating steelhead passage at Calaveras Dam and Alameda Creek Diversion Dam. The following creeks are found in this subwatershed: Arroyo Hondo, Calaveras Creek, Isabel Creek, Long Branch, Hog Slough, Smith Creek, and Sulphur Creek.
Upper Alameda Creek is a 74-square-mile subwatershed of the Alameda Creek Watershed, and extends from Sunol south, to just northeast of Mount Hamilton. Alameda Creek in its entirety is a large, 45-mile long creek, which starts in the rugged hills of the Diablo Range and flows northwest through broad Sunol Valley, then turns west to run through steep Niles Canyon. “Upper” Alameda Creek becomes “Lower” Alameda Creek about midway through the canyon. Efforts are underway to aid steelhead migration into upper Alameda Creek above Little Yosemite and the Alameda Diversion Dam, eight miles below the headwaters of Alameda Creek. Most of the protected, undeveloped land in the Upper Alameda Creek subwatershed is public land managed by the SFPUC and the East Bay Regional Park District, or owned by ranchers. There is very little development or access other than the Sunol Regional Wilderness, where the headwaters of Upper Alameda Creek can be explored. Many miles of trails lead from this point, some following shady creek banks and others climbing grassy ridges to high peaks. The following creeks are found in this subwatershed: Alameda Creek east of Stonybrook Creek, Stonybrook Creek, Sheridan Creek, Pirate Creek, Welch Creek, Leyden Creek, Indian Joe Creek, Whitlock Creek, and Valpe Creek.
San Antonio is a 40-square-mile subwatershed of the Alameda Creek Watershed located in Unicorporated Alameda County, and is very sparsely populated with most of the land being managed for grazing and watershed protection. Several creeks drain this watershed, all flowing north into San Antonio Reservoir. The Reservoir is fed primarily by Indian Creek and San Antonio Creek, and is part of the City of San Fransisco’s water supply system. It can be filled with Hetch Hetchy aqueduct in addition to the natural creek flow. Indian Creek drains the south side of Wauhab Ridge in the Ohlone Regional Wilderness and flows west to drain the north side of Valpe Ridge. Turning northwest, it then drains the east side of Apperson Ridge and flows to San Anonio Reservoir. San Antonio Creek drains Rowell Ridge in the Ohlone Regional Wilderness and flows northwest where it is joined by La Costa Creek before flowing to the east side of San Antonio Reservoir. La Costa Creek drains the north side of Wauhab Ridge in the Ohlone Regional Wilderness then flows northwest to meet San Antonio Creek. Water released from the dam flows northwest into Alameda Creek. The following creeks are found in this subwatershed: San Antonio Creek, Apperson Creek, La Costa Creek, Indian Creek, and the San Antonio Reservoir.
Arroyo Del Valle is a 168-square-mile subwatershed of the Alameda Creek Watershed. Arroyo del Valle begins in the rugged mountains of the Diablo Range and flows northwest toward Livermore Valley. Before reaching the valley, it is impounded to create Lake Del Valle. Lake Del Valle is a reservoir owned by the California Department of Water Resources and is part of the State Water Project, which provides the majority of Zone 7 Water Agency’s water supply. Lake Del Valle also collects and stores local runoff for Zone 7 and the Alameda County Water District. Zone 7 manages the Arroyo Del Valle subwatershed, and has purchased approximately 5,000 acres of rangeland near Lake Del Valle for the purposes of watershed protection using integrated management methods. The East Bay Regional Park District manages Del Valle Regional Park, where visitors can enjoy swimming, fishing, boating, camping and hiking in and around the lake. Once released at the dam, Arroyo Del Valle flows along the south side of the valley draining much of the southern portion of the city of Livermore and flows through and drains a considerable fraction of the city of Pleasanton, where it joins Arroyo de la Laguna in Pleasanton. The following creeks are found in this subwatershed: Arroyo del Valle (also known as Arroyo Valle), Dry Creek, Shafer Creek, Trout Creek, Sycamore Creek, Colorado Creek, Arroyo Bayo, San Antonio Creek, Jumpoff Creek, Sulphur Springs Creek, Sweetwater Creek, Beauregard Creek, and Lake Del Valle.
Arroyo Mocho is a 54-square-mile subwatershed of the Alameda Creek Watershed which drains a narrow rugged canyon that extends approximately 20 miles southeast of Livermore, to its headwaters in northern Santa Clara County. The Arroyo Mocho flows west along Mines Road in Livermore, through Pleasanton, and eventually joins South San Ramon Creek to become Arroyo de la Laguna, which flows into Alameda Creek. The following creeks are found in this subwatershed: Arroyo Mocho, Tunnel Creek, and Mendenhall Springs.
The following information pertains to the southern section of the Upper Alameda Creek Watershed.
Del Valle Regional Park is 4,395 acres with a five-mile-long lake available for a variety of water-oriented recreation such as fishing, swimming, sailing and windsurfing. The park contains a family campground, equestrian camping and trails, and a boat launch and rentals. You’ll also find a great network of hiking trails for exploring the park and viewing wildlife.
You can reach this park by foot, horse or bicycle on the South Livermore Valley Trail from Arroyo Road or Marina Avenue. You can also park at the parking lot at the end of Hansen Road. A multi-use trail for hiking, bicycle and horseback riding passes through Holdener Park. The open space area surrounding the trail has grasslands where spring wildflowers make an appearance, and provides for a great place to view wildlife.
The Ohlone Regional Wilderness is 9,737 acres and is only accessible by the Ohlone Wilderness Trail. It includes 3,817-foot Rose Peak and Murrietta Falls, the tallest waterfall in the Bay Area. This is a vast wilderness away from populated areas, and is inhabited by endangered bald eagle, mountain lions, bobcats, deer, and a herd of Tule Elk. The Ohlone Wilderness Regional Trail Hiking Permit/Map is required for day use and camping. The entry points to this area are Del Valle Regional Park to the northeast and Sunol Regional Wilderness to the west.
This 6,859-acre park was mostly former ranch land that continues have cattle grazing. The park attracts thousands of visitors a year and offers camping, picnicking, hiking, back-packing and equestrian trails. A highlight in the park is the Little Yosemite Area. Explore the headwaters of Alameda Creek, the county’s largest creek. Many miles of trails lead from this point, some following shady creek banks and others climbing grassy ridges to high peaks.
Located in beautiful Sunol Valley, within the Alameda Creek Watershed, the Sunol AgPark is owned by the San Francisco Public Utilities Commission and managed through a partnership agreement with the Alameda County Resource Conservation District. This partnership provides land and technical assistance to the farmers and hands-on environmental education programs for Bay Area schoolchildren. Within the AgPark, small-scale organic farms produce fresh foods and flowers for diverse Bay Area communities. Plans for an Alameda Creek Watershed Center are underway at the Agpark.
This beautiful City of Livermore park preserves a two-mile-long reach of the braided channel and valley floor of Arroyo del Valle. Studded with large sycamores and crossed by a complex of channels and gravel bars, visitors can hike a network of trails. The channels and gravel bars were active parts of the flood plain before Del Valle Reservoir was built upstream, and are still occasionally inundated when water is released from the dam during large floods. Natural stream terraces host vineyards along the margins of the valley.
Restoration efforts are ongoing in the southern section of the Upper Alameda Creek Watershed. Some of the largest projects are tied to the dams and reservoirs unique to this portion of the watershed, while other efforts span the entire watershed, such as fish passage improvements, watershed protection and riparian habitat restoration.
Dam Enhancements & Fish Passage Improvements
All three of the dams and reservoirs in this portion of the watershed were constructed prior to 1970, but the oldest of the three – Calaveras – was built in 1925, making it nearly 100 years old. In 2011, the San Francisco Public Utilities Commission (SFPUC) began work to address the aging dam via the Calaveras Dam Replacement Project (part of the larger Water System Improvement Program). The project consists of constructing a new earth and rock fill dam just downstream from the existing dam. The new dam will allow for a significant increase in reservoir capacity and be more seismically sound.
Fish passage around the dam will also be improved via the release of water into Alameda and Calaveras Creeks from Calaveras Reservoir. These releases will provide important cold-water inputs, which will help create better quality habitat for trout spawning and rearing in the creeks. Complementing these efforts in Alameda Creek is the construction of a fish ladder and screens at the Alameda Creek Diversion Dam.
Throughout the watershed, agencies and organizations are working on a variety of other projects to remove other barriers to fish migration and improve upstream passage as well. Large boulders, gas pipelines, old culverts, and other in-stream barriers to migration are being studied and altered in ways that will allow for more successful fish passage up- and downstream.
A number of agencies operating in this portion of the watershed own and manage lands to protect watershed health and ensure water quality. San Francisco Public Utilities Commission owns 36,000 acres in this area – approximately 1/3 of the entire Alameda Creek Watershed. These lands surround both the San Antonio and Calaveras Reservoirs. Development on this land is limited, with nearly 90% managed as open space for grazing. East Bay Regional Park District owns or manages approximately 12,000 additional acres in this portion of the watershed – all of which they manage for both the preservation of natural resources and recreation. In 2013, Zone 7 Water Agency purchased the Lake Del Valle Watershed Property, a 5,000-acre area of land primarily situated within the Arroyo del Valle subwatershed. The primary goal of this purchase was to protect the land from development and allow Zone 7 to manage the land in a way that would minimize pollution and erosion inputs to Del Valle Reservoir. Currently, the land is grazed in accordance with the agency’s watershed management objectives.
Native Habitat Restoration
A variety of organizations and agencies engage regularly in large- and small-scale habitat restoration efforts throughout the southern section of the Upper Alameda Creek Watershed. Some of these efforts focus on rehabilitating riparian areas through channel improvements, streambank revegetation, invasive species removals, and native species planting. In other portions of this section of the watershed, agencies are working to restore floodplains, which will help to naturally reduce flooding and put native plants and trees back in areas where they historically existed. In the upper reaches of this portion of the watershed, habitat is being managed to prevent erosion and downstream sedimentation, and to protect special status species.
The East Alameda County Conservation Strategy is a large-scale effort which will help develop a long-term plan for habitat protection and encourage the implementation of conservation stewardship projects by public agencies and landowners throughout the area to help offset impacts from local land use, transportation or other infrastructure projects.
The Alameda Creek Watershed historically had healthy populations of anadramous fish – specifically, steelhead trout. Instream habitat quality throughout major portions of Alameda Creek has been limited by reduced habitat complexity and migration barriers. Nearly a dozen agencies and organizations work closely as the Alameda Creek Fisheries Restoration Workgroup to collaboratively address the local implications of the steelhead trout being placed on the federal Endangered Species List and pursue steelhead restoration. Numerous local agencies are also working directly with the National Marine Fisheries Service through a cooperative agreement on their preparation of a Recovery Plan to address steelhead recovery throughout the Bay Area, including a specific vision for steelhead restoration in the Alameda Creek Watershed.
There are a number of groups and organizations who provide opportunities for individuals to get involved in many ways in the southern section of the Upper Alameda Creek Watershed. The Tri Valley Creeks Adopt a Creek Spot Program is a partnership program that encourages the public to get involved to reduce litter and allows participants to help improve water quality and aquatic habitat in neighborhood creeks. The Alameda Creek Alliance works to restore native species and habitats and to protect undeveloped areas within the watershed. It hosts an informative and well-organized website with an abundance of information about these efforts. The Alameda Creek Watershed Forum (acwForum) coordinates multiple stakeholders to protect and enhance beneficial water-related uses and resources in the watershed. The acwForum hosts an annual conference and coordinates or sponsors specific projects, such as creek and watershed signage, “adopt a spot” areas, and a sediment forum. The San Francisco Estuary Institute’s Alameda Creek Historical Ecology Study provides in-depth analysis that informs current salt marsh and steelhead restoration efforts in the watershed. The East Bay Regional Park District and the Regional Parks Foundation provide many opportunities for volunteerism and education within the watershed. Living Arroyos is a multi-agency partnership to enhance and maintain the urban streams and streamside habitats of the Livermore-Amador valley, and conducts community workdays.
Resources in the Watershed
- Alameda Countywide Clean Water Program
- Alameda County Conservation Partnership
- Alameda Creek Alliance
- Alameda Creek Watershed Forum
- Oakland Museum of California’s Guide to Bay Area Creeks
- East Bay Regional Park District
- Living Arroyos
- Friends of the Arroyos
- Granada Native Gardens
- San Francisco Public Utilities District
- Livermore Area Recreation and Parks District
- Tri Valley Creeks Adopt a Creek Spot
- City of Pleasanton
- City of Livermore
- Zone 7 Water Agency