|Location||Bay Area, Northern California|
|Etymology||The Karkin people|
|River sources||Sacramento River, San Joaquin River|
|Primary outflows||San Pablo Bay, San Francisco Bay|
|Basin countries||United States|
|Max. length||8 miles (13 km)|
|Settlements||Benicia, Crockett, Martinez, Vallejo|
The Carquinez Strait ( // ) is a narrow tidal strait in Northern California. It is part of the tidal estuary of the Sacramento and the San Joaquin rivers as they drain into the San Francisco Bay. The strait is eight miles (13 km) long and connects Suisun Bay, which receives the waters of the combined rivers, with San Pablo Bay, a northern extension of the San Francisco Bay.
The strait formed in prehistoric times, near the close of one of the past ice ages, when the Central Valley was a vast inland lake. Melting ice from the Sierra Nevada raised the water level while seismic activity created a new outlet to the Pacific Ocean, draining the lake into the ocean and exposing the valley floors.
Andrei Sarna-Wojcicki, a geologist emeritus of the US Geological Survey (USGS), estimates that the Carquinez Strait was likely formed about 640,000 to 700,000 years ago, while much of modern California was emerging from an ice age. The present Sacramento Valley and San Joaquin Valley were covered by a huge lake (now extinct), which has been called Lake Corcoran. Initially, this lake drained into the ocean through a valley near present-day Monterey. However, ongoing seismic activity raised the coastal mountains sufficiently to plug this outlet. Concurrently, ice melting off the Sierras raised the water level in Lake Corcoran until the lake began to carve a new outlet to the ocean. At some point, the coastal barrier collapsed between today's cities of Crockett and Benicia, releasing lake water in a cataclysmic flood.
The strait forms part of the county border between Solano (to the north) and Contra Costa (to the south), and it's approximately 15 mi (25 km) north of Oakland. The cities of Benicia and Vallejo lie on the north side of the strait, while Martinez, Port Costa, and Crockett sit on the southern coast. The Napa River joins the strait, via the short Mare Island Strait, near its entrance into San Pablo Bay. Its watershed covers 62,500 square miles (162,000 km2), approximately 40 percent of California's total surface.
The strait is named after the Karkin people (los Carquines in Spanish), a linguistic division of the Ohlone indigenous peoples who resided on both sides of the strait.
The California Maritime Academy is at the western end of the strait on the northern waterfront. The C&H Sugar refinery is located on the southern shore in the small town of Crockett.
The strait is crossed by two highway bridges: the Carquinez Bridge on Interstate 80 and the Benicia–Martinez Bridge on Interstate 680. Each highway bridge consists of two spans.
Interstate 780 connects the two highways on the northern slope of the strait. State Route 4 connects these highways south of and inland from the strait.
A rail bridge just east of the Benicia–Martinez Bridge is used by the Capitol Corridor, California Zephyr, and Coast Starlight trains. A rail ferry, with the ferries Contra Costa and Solano provided service across the strait near the location of the current rail bridge until the rail bridge was built in 1930.
Tall pylons carrying power lines cross the strait as well. The Carquinez Strait Powerline Crossing was the world's first powerline crossing of a large river.
The channel is navigable and is used for commercial and military shipping. Deep water ship traffic bound for both the Port of Sacramento and the Port of Stockton traverse the strait through the Stockton Deepwater Shipping Channel and Sacramento Deep Water Ship Channel. Carquinez Strait is part of the Baldwin Deepwater Shipping Channel.
The narrow gap in the Coast Range that forms the strait has led to the formation of the San Joaquin–Sacramento River Delta, an inverted river delta, upstream of it, a rare geological feature. The strait is too small to allow the passage of huge amounts of floodwaters created during years with heavy rainfall/snowmelt events. Because the Delta area is the first to fill and last to drain in a flood event, silt and soil have more time to drop out of suspension, creating the inverted river delta feature.
Seawater is more dense than fresh water because of its higher concentration of salts. Under stable conditions, this means that an invisible boundary forms where two such streams meet, as where the fresh water from Sacramento and San Joaquin Rivers meet the sea water contained in the San Francisco Bay.
By the early 20th century, farmers in the Sacramento-San Joaquin Delta, who depended on irrigating their fields with fresh water from the two rivers noticed an increase in salinity farther inland than before. It became obvious that fresh water was being pumped out of the Delta faster than it could be replenished by rain and snow during the wet season. Farmers, businessmen and politicians complained that allowing fresh water to flow to the ocean was wasteful. While many solutions were proposed, few appeared practical. A political consensus formed that damming the Carquinez Strait should solve the seawater intrusion problem.
In September 1923, the California Legislature appropriated $10,000 (equivalent to $152,000 today) for a saltwater dam survey. The Federal government added a $20,000 contribution ($304,000 today) through the US Reclamation Service. Under Reclamation Service rules, another $10,000 needed to be raised from local supporters of the project. The necessary money was raised by March 1924, and the first of three site surveys was announced.
The first survey was at Army Point, near Benicia, which was the preferred site based on preliminary studies. The second choice was Dillon Point, near Southampton Bay, while the third survey was at San Pablo Point, near Richmond. The three surveys were completed by the end of 1924. However, it took four years to complete the decision-making process that officially named Army Point as the future dam site. Still more wrangling in the legislature was required before the "Salt Water Barrier" was officially adopted in May 1929, and made part of the state water conservation project.
On January 24, 1930, with the Great Depression taking hold, President Herbert Hoover cancelled the Carquinez Strait project, saying that it was too costly. All efforts to revive the project failed. Years later, the Central Valley Project attempted to mitigate the effects of seawater intrusion by constructing other dams much farther inland and canals to send fresh water to the San Joaquin Valley.
San Francisco Bay is a shallow estuary in the U.S. state of California. It is surrounded by a contiguous region known as the San Francisco Bay Area, and is dominated by the large cities of San Francisco, San Jose, and Oakland.
The Sacramento River is the principal river of Northern California in the United States and is the largest river in California. Rising in the Klamath Mountains, the river flows south for 400 miles (640 km) before reaching the Sacramento–San Joaquin River Delta and San Francisco Bay. The river drains about 26,500 square miles (69,000 km2) in 19 California counties, mostly within the fertile agricultural region bounded by the Coast Ranges and Sierra Nevada known as the Sacramento Valley, but also extending as far as the volcanic plateaus of Northeastern California. Historically, its watershed has reached as far north as south-central Oregon where the now, primarily, endorheic (closed) Goose Lake rarely experiences southerly outflow into the Pit River, the most northerly tributary of the Sacramento.
The Central Valley is a broad, flat valley that dominates the interior of California. It is 40 to 60 miles wide and stretches approximately 450 miles (720 km) from north-northwest to south-southeast, inland from and parallel with the Pacific coast. It covers approximately 18,000 square miles (47,000 km2), about 11% of California's land area. The valley is bounded by the Coast Ranges to the west and the Sierra Nevada to the east.
The San Joaquin River is the longest river of Central California. The 366-mile (589 km) long river starts in the high Sierra Nevada, and flows through the rich agricultural region of the northern San Joaquin Valley before reaching Suisun Bay, San Francisco Bay, and the Pacific Ocean. An important source of irrigation water as well as a wildlife corridor, the San Joaquin is among the most heavily dammed and diverted of California's rivers.
The Central Valley Project (CVP) is a federal power and water management project in the U.S. state of California under the supervision of the United States Bureau of Reclamation (USBR). It was devised in 1933 in order to provide irrigation and municipal water to much of California's Central Valley—by regulating and storing water in reservoirs in the northern half of the state, and transporting it to the water-poor San Joaquin Valley and its surroundings by means of a series of canals, aqueducts and pump plants, some shared with the California State Water Project (SWP). Many CVP water users are represented by the Central Valley Project Water Association.
San Pablo Bay is a tidal estuary that forms the northern extension of San Francisco Bay in the East Bay and North Bay regions of the San Francisco Bay Area in northern California.
Suisun Bay is a shallow tidal estuary in Northern California. It lies at the confluence of the Sacramento River and San Joaquin River, forming the entrance to the Sacramento–San Joaquin River Delta, an inverted river delta. Suisun Marsh, the tidal marsh land to the north, is the largest marsh in California. Grizzly Bay forms a northern extension of Suisun Bay. Suisun Bay is directly north of Contra Costa County.
An inverted river delta is special category of river delta in which the narrow end of the delta emerges on the seafront and the wide end is located further inland, so that with respect to the seafront, the locations of both ends of the delta are inverted.
Benicia State Recreation Area is a state park unit of California, United States, protecting tidal wetland. It is located in the Solano County city of Benicia, 2 miles (3.2 km) west of downtown Benicia and borders Vallejo's Glen Cove neighborhood. The park covers 447 acres (181 ha) of marsh, grassy hillsides and rocky beaches along the narrowest portion of the Carquinez Strait. Southampton Creek and the tidal marsh front Southampton Bay, where the combined waters of the Sacramento and San Joaquin Rivers approach San Pablo Bay, the northern portion of San Francisco Bay.
The Sacramento–San Joaquin River Delta, or California Delta, is an expansive inland river delta and estuary in Northern California. The Delta is formed at the western edge of the Central Valley by the confluence of the Sacramento and San Joaquin rivers and lies just east of where the rivers enter Suisun Bay. The Delta is recognized for protection by the California Bays and Estuaries Policy. Sacramento–San Joaquin Delta was designated a National Heritage Area on March 12, 2019. The city of Stockton is located on the San Joaquin River on the eastern edge of the delta. The total area of the Delta, including both land and water, is about 1,100 square miles (2,800 km2). Its population is around 500,000 residents.
The Carquinez Bridge is a pair of parallel bridges spanning the Carquinez Strait at the northeastern end of San Francisco Bay. They form the part of Interstate 80 between Crockett and Vallejo, California.
The California State Water Project, commonly known as the SWP, is a state water management project in the U.S. state of California under the supervision of the California Department of Water Resources. The SWP is one of the largest public water and power utilities in the world, providing drinking water for more than 23 million people and generating an average of 6,500 GWh of hydroelectricity annually. However, as it is the largest single consumer of power in the state itself, it has a net usage of 5,100 GWh.
The Solano was a large railroad ferry, built as a reinforced paddle steamer with independently powered sidewheels by the Central Pacific Railroad, that carried entire trains across the Carquinez Strait between Benicia and Port Costa in California, daily for 51 years from 1879 to 1930. When launched, the Solano was the largest ferry of its kind in the world, a record held for 35 years until 1914 when she was joined by her sister ship, the Contra Costa, which was 13 feet longer.
The North Bay Aqueduct (NBA) is part of the California State Water Project. The aqueduct is 27.4 miles (44.1 km) long all in pipelines and serves Napa and Solano counties, California.
Sherman Island is an island in the Sacramento-San Joaquin River Delta at the confluence of the two rivers in Sacramento County, California, 1.2 miles (1.9 km) northeast of Antioch. The 5,500 ha island, mostly managed by Reclamation District 341, is the meeting point of Sacramento, Solano, and Contra Costa Counties, and is bordered on the north and northwest by the Sacramento River, on the northeast by Three Mile Slough, and on the east, and south west by the San Joaquin River. Sherman Island is a widely known kite and windsurfing area.
Delta and Dawn, also known as the Delta whales, were two humpback whales, a mother and her calf, which entered San Francisco Bay in early May 2007. They swam up the Sacramento River approximately 90 nautical miles (170 km) upstream from the Golden Gate, about 20 miles (32 km) further inland than Humphrey the Whale had gone two decades earlier. Under the Endangered Species Act, California state officials were required to rescue the animals. Their journey was thought to be the longest freshwater incursion by humpback whales.
Ryer Island is an island in Suisun Bay at the mouth of the Sacramento-San Joaquin River Delta in Solano County, California, eight miles east-northeast of Benicia. It is administered by Reclamation District 501, and is in the Suisun Resource Conservation District. At the time of statehood it was known as Kings Island, and is labeled as such on an 1850 survey map of the San Francisco Bay area made by Cadwalader Ringgold as well as an 1854 map of the area by Henry Lange. It is labeled, along with Deadman Island, Joice Island, Grizzly Island, Simmons Island, and Roe Island, on a 1902 USGS map of the area.
Lake Corcoran is an ancient lake that covered the Central Valley of California.
Stockton Deepwater Shipping Channel also called the Baldwin-Stockton Deepwater Shipping Channel or Stockton Deep Water Channel is a manmade deepwater water channel that runs from Suisun Bay and the Sacramento River - Sacramento Deep Water Ship Channel to the Port of Stockton and the Stockton Channel in California. The Stockton Ship Channel is 41 mi (66 km) long and about 37 ft (11 m) deep, allowing up to Panama Canal size ocean ships access to the Port of Stockton at the City of Stockton. The Stockton Deepwater Shipping Channel is part of the vast Sacramento–San Joaquin River Delta that has a connection to the Pacific Ocean. Stockton Deepwater Shipping Channel is also called the lower San Joaquin River.
Van Sickle Island is an approximately 10,000-acre (4,000 ha) island in Suisun Bay, California. It is part of Solano County, and administered by Reclamation District 1607. Its coordinates are, and in 1981 the United States Geological Survey recorded its elevation as 0 ft (0 m). The island's land is divided into 22 privately-owned parcels, used primarily for duck clubs and private residences. A railroad bridge constructed in 1913 once connected it to Montezuma and Chipps Island, from which a ferry connected to Mallard Island and Pittsburg. The rail service was discontinued and the bridges no longer exist; currently, the island is accessible by water, as well as by road on bridges from Hammond Island and Wheeler Island.