Starting in 1990 and up to the present state and federal agencies have been looking at ways to revised the flow of water through the Delta to increase water exports and increase the quality of the water exported.  There are also literally thousands of studies and reports regarding proposals to revise the Delta to change the environment to something similar to what the San Joaquin River looked like in the 1850's when California became a state.  However, since most of the Delta lands are privately-owned, changes to waterflow may impact in-delta water use and rights, and may destroy some of the prime farm lands of the Delta,.  If you want to see the history of planning for revisions to the Delta, go to http://DeltaREvision.com and to the "planning" maps or the links by year.