Wednesday February 8, 2012

The Sacramento-San Joaquin Delta is a complex system to navigate and structures like the Delta Cross Channel (DCC) gates can turn a navigable waterway into an unexpected dead end. The DCC was constructed in 1951 to divert water from the mainstem of the Sacramento River into the Mokelumne River and through the interior Delta. The United States Bureau of Reclamation (USBR) built the DCC as a response to saltwater intrusion into the Delta, which occurs when water is exported from the South Delta. The gates can be opened and closed depending on water quality, flood protection, and fish protection requirements.

There are many structures in the Delta and Suisun Marsh designed to control salinity and water quality levels. Salinity intrusion is a major concern for agricultural and municipal water users that draw water from the Delta. Water managers use the 2 practical salinity unit isohaline, better known as “X2”, for tracking the direction and magnitude of fluctuations in salinity. The X2 is tracked as the distance upstream from the Golden Gate and is maintained by releasing water from upstream reservoirs and adjusting export rates. The position of the X2 is legally established through the 2008 biological opinion (OCAP) and subsequent court decisions.
The Suisun Marsh Salinity Control Gates (SMSCG) are large, radial arm floodgates similar to the DCC, which restrict the flow of high salinity water from Grizzly Bay into Montezuma Slough and maintain lower salinity in the brackish marsh. Additionally, the California Department of Water Resources (DWR) annually installs three agricultural barriers and one fish barrier in the South Delta. The agricultural barriers in Old River, Middle River and Grant Line are rock barriers designed to increase water height, circulation, and quality. The Head of Old River Barrier (HORB) is a fish barrier designed to improve operational flexibility of the State Water Project and help reduce fishery impacts by preventing migrating fish from entering Old River. Before heading out to explore the California Delta it’s best to do your homework and check on the status of the delta structures to prevent running into a dead end.

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