The twin 40-mile tunnels would carry water from the Delta to Central and Southern California. The state says the $15 billion project would be less environmentally-intrusive than the current system.
Barbara Barrigan-Parrilla of the group Restore the Delta calls it "the worst and most expensive, low-value public works project ever proposed in the history of California."
She says saltwater would fill the Delta in its place.
"We will lose everything from sand hill cranes to salmon; our Delta farming communities will never recover," says Barrigan-Parilla. "The urban surrounding areas that are tied to that healthy Delta economy will go into permanent recession."
State officials point out the water will still have to comply with federal standards
"There’s no apocalyptic encroachment of salt that would happen were this project to be built," says Nancy Vogel, deputy secretary of the Natural Resources Agency.
"When you move water, naturally, it can pit one group of water users against another," says Vogel. "So I think we’ll always face challenging decisions in the Delta."
Opponents expect to submit 30,000 comments before the deadline.