North Bay Aqueduct

This article relies largely or entirely on a single source. Relevant discussion may be found on the talk page. Please help improve this article by introducing citations to additional sources. Find sources: "North Bay Aqueduct" – news · newspapers · books · scholar · JSTOR (October 2013)

The North Bay Aqueduct (NBA) is part of the California State Water Project that was built in two phases, Phase I (1967-1968) and Phase II (1985-1988).^[1] The aqueduct is 27.4 miles (44.1 km) long all in pipelines and serves Napa and Solano counties, California. The aqueduct provides water to about 500,000 residents in Solano and Napa.

The State Water Project diverts water originating from the Sacramento and San Joaquin Rivers (and their tributaries), and it stores water in Lake Oroville. The North Bay Aqueduct was envisioned as part of the State Water Project during the 1950s and 1960s when the project was being planned. Initial North Bay Aqueduct water service went to Benicia and Vallejo. In 1990, the North Bay Regional Water Treatment Plant, serving Fairfield and Vacaville, came on line and was able to treat water from the North Bay Aqueduct for these two cities. The aqueduct cost approximately $83 million to construct.

The North Bay Aqueduct is an underground pipeline that runs from Barker Slough in the Sacramento-San Joaquin River Delta to Cordelia Forebay, just outside Vallejo. From the Cordelia Forebay water is pumped to Napa County, Vallejo and Benicia. Travis Air Force Base is also served off the NBA. It is an enclosed pipeline between Barker Slough and Cordelia Forebay.^[2] The size of the underground pipeline varies from 72 inches at Barker Slough to 54 inches at Cordelia Forebay. The NBA is operated remotely by the State Department of Water Resources (DWR) at the Delta Field Division office near Tracy.

The aqueduct cannot deliver the full 175 cfs flow it was designed and contracted for. Pumping tests have shown that it can deliver a maximum of 142 cfs. DWR, SCWA and Napa County are investigating methods to increase the capacity of the NBA at least to the contract amount of 175 cfs. Peak pumping occurs during the summer between 50-125 cfs, while during the winters rates are between 0-49 cfs.^[3] The North Bay Aqueduct has been used to meet with salinity objectives in the western Suisun Marsh by pumping water at Barker Slough and releasing it into Green Valley Creek, and the flow is effective in lowering salinity.

There are restrictions on pumping in order to protect the Delta smelt and longfin smelt. Restoration efforts are conducted in order to protect endangered fish species.