As referenced elsewhere, the Sacramento/San Juaquin estuary (Delta) is under increasing strain, and the poulders which constitute it's principle economic wealth, (farming) will not be sustainable long with rising water predicted from global warming .
When (not if) this occurs, the prior tideland marsh (from 100 years ago) will become an extension of the San Fransicso Bay, with greatly increased salinity.
This will make the water currently extracted at the Southern end of the Delta (to keep all our Southern California friends un-thirsty) non-potable. (as well as having many other undesirable effects on groundwater.
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The Delta connects with the San Franciso bay through the Straits of Carquinez.
Consideration should be given to installing a heavy fabric float-supported membrane in the straits which has the effect of reducing salt water incursion during incoming tides. Ship traffic could be constrained to only "low tide" periods, when fresh water outflow is assured.
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would this work?