Bay-Delta salinity – a brief history

Thanks to Controversy (the Journalist’s Best Friend), the subject of salinity in the Sacramento-San Joaquin-San Francisco Bay Delta system has received more attention of late than is usually attached to such arcane topics. But I did not realize how old this issue is.

courtesy Delta Stewardship Council

It was salinity and fish science that caused federal Judge Oliver Wanger to famously tee off on a pair of U.S. Fish and Wildlife Service scientists back in September. The underlying issue is that water removed from the Sacramento and San Joaquin systems that would otherwise have reached the estuary between fresh and salt water changes the system’s salinity. More fresh water flowing to the sea pushes salt water out of the system. Less allows the salt water to flow back in, through Suisun Bay and into the delta. This plays a role in the life history of the endangered delta smelt, which makes salinity a pertinent question in California’s tangled water management these days.

As Felicity Barringer explains it:

The area of ideal salinity for the smelt shifts back and forth, eastward and westward, depending on the time of year, the amount of rain and the decisions of federal and state water managers. (A fuller explanation with diagrams can be found at the Bay Delta Blog.)

This zone of ideal salinity for young smelt to feed is known as the X2; the Interior Department had decided that in wet years like this one, it should be no farther than 46 miles east of the Golden Gate Bridge. The decision was challenged in the lawsuit by the state and agricultural water interests, which prefer that less go out to the bay.

Pronouncements by two federal scientists on the issue drew Wanger’s ire, which made salinity the hot combat science topic of this past fall in California politics. But I was struck in reading Philip Garone’s environmental history of California’s Central Valley to learn how long this problem has existed.

The first irrigation diversions upstream of the delta date to 1852, and by the 1870s enough water was being taken out of the rivers to make a noticeable change in the delta. As rice farming expanded, the problems increased:

When a record 164,000 acres of rice cultivation coincided with a serious drought in 1920, the salinity problem in the Delta reached crisis proportions. In July of that year, the western Delta city of Antioc, situated near the mouth of the San Joaquin River, together with ninety-seven Delta landowners, brought suit against upstream irrigators in the Sacramento Valley. The plaintiffs requested that the irrigators be enjoined from diverting so much water from the Sacramento River and its tributaries that tidal salinity would advance far enough into the Delta to threaten Antioch’s municipal water supply, which was drawn from the San Joaquin River.

Antioch lost, the court ruling that it had no right to unsalted water if that meant someone upstream had to stop diverting. But efforts to deal with the issue in a long term fashion, Garone writes, eventually led to the creation of the Central Valley Project. Which is what led federal scientists back into court this year talking about salinity.


  1. Salinity intrusion from the San Francisco Bay 1t is not smelt’ problem,but salinity intrusion into Deltaic tributaris. especially under conditions of excessive, current cumulative water withdrawals,will represent a mortal blow for water supply to North and South. Note that It had taken place in 1920h (Dept. of Public work,1928), and else. To wash out salt from the Delta will require millions of AF to have Contra Costa county and water conveyance facilities tofunction for numerous public needs needs.

  2. Add this to your history of salinity in the Bay/Delta John :

    In 1906, the California and Hawaiian Sugar Refining Company (C&H) began refining pure cane sugar in the small town of Crockett, California at the confluence of the Carquinez Staits and San Pablo Bay, fully 20 miles west of the current X2 point.They chose the location for access to shipping , rail and FRESH water.On occasion in dry years they would send water barges up river as far as Antioch to retrieve FRESH water.

    I find this an interesting factoid as I watch convoluted discussions about salinity, X2 locations and their effects on the fishery.

  3. Chris – Thanks. Can you point me to more info/citation/etc on C&H? That’s a great tale I’d like to read more on.

    Michael – Thanks for your comments, and for starting me down the Google path that led me to your September submission to the Delta Stewardship Council of the Luna Leopold review of salinity issues.

  4. There is a lot of interesting history and paleohistory of Delta salinity. The Delta, which only formed 6,000 years ago at its current location as a by-product mostly of sea level rise. At the end of the last Ice Age, with lower sea levels, it was outside the Golden Gate. Different parts of the Delta system have always had very different salinities. Suisun Marsh area seems most important here. The records of water foraging for the C&H sugar plant show interesting seasonal, drought, and historical trends in salinity in the early 1900s. Our books on Envisioning Futures for the Sacramento San Joaquin Delta and Comparing Futures for the Sacramento San Joaquin Delta present some of this history, including some of the C&H data. The 1920 Antioch case echos on, in many ways.

  5. At the above website, you will find a complete discussion of the history of salinity in the Detla, including references to paleo-salinity studies going back several thousand years. The main document is:
    It includes an analysis of the C&H data, and compares the distances from Crockett to the 50 mg/l chloride line (“X 0.2”, not X2) measured by C&H to the distance required in the 1960’s and more recently–all in periods with similar hydrology. It confirms the obvious: when 50% of the fresh water is taken from the system, the Delta gets more saline.
    Greg Gartrell
    Contra Costa Water District

  6. Lots of archival documents available at the above website, listed by “issue”. The conflicts in waterflow reporting methods over the last 10 years, if allowed to continue, will result in further encroachment of salinity into the prime Delta farmlands. Thanks to Greg above for the note regarding X2 vs the water standard x 0.2

  7. An important piece of history that the author overlooks is the role played by the State and federal water projects in preventing salinity from reaching far into the Delta. DWR maps show that in 1931, prior to the water projects, salt water reached as far into the Delta as Walnut Grove. Since the projects became operational, the salinity intrusion has gone no further inland than the southern tip of Brannan Island, a significant benefit. It is also important to realize that this improved effort to push back the salinity coincides with operations that allow the water projects to deliver water to farms and cities in the Sacramento Valley. The result of these water deliveries is a supply of water that is used to produce a safe and healthy food supply while providing jobs for thousands.

    Mike Wade
    California Farm Water Coalition

  8. jfleck- Jay Lund accurately guessed my source.
    Both studies are a good read. Regardless whether you agree with the conclusions reached, there is much information to be gleaned.

    Greg Gartrell- Thanks for the informative link and the X2 /x 0.2 clarifcation.

    Mike Wade- Where to start ?
    The jury is out on whether occasionally “preventing salinity from reaching far into the Delta” is any more beneficial or damaging than allowing fresh water to intrude deep into San Pablo Bay.
    Perhaps you would benefit from reading the studies cited by Jay Lund.
    As for salinity not penetrating the delta further than Brannon Island ? Hogwash !
    Not only are you technically incorrect your inference that this is somehow a magnanimous benefit is ridiculous. The only reason salinity is not allowed to routinely penetrate further than Brannon Island is that pesky little contract between the state of California and the North Delta Water Agency ( of which I am a member).
    If, as Nicky Suard points out, we can’t agree on methods of reporting and common definitions of terminology we are only left with talking point and twisted logic.

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