Captain Karen Mann has been coming to the delta since she was a little girl.  Now she and her husband live in Discovery Bay, and fish with their grandkids from their boat, the Karen Jane. She says she's worried the state's plan to build a canal would destroy the delta ecosystem.

MANN: "It would break my heart.  It would just change the delta, the character of the delta so much."

Right now, two pumps at the southern end of the delta take water for more than 20 million people in Southern California and agriculture in the Central valley. These pumps sometimes suck in endangered species of salmon and smelt -- and can pull in so much water they make rivers run backwards.

The state proposal to pump fresh river water from north of the delta via a giant canal could ease this pressure. 

But delta farmland owner Mike Robinson says the whole point of taking water from the south end of the delta was to keep freshwater flowing through the whole system.

ROBINSON: "If the water flows through, everybody benefits. The exporters benefit, the locals benefit-- nobody has an advantage."

But if the canal plan goes through, Robinson says the incentive to maintain a healthy delta is gone.  And he says, diverting freshwater from ever entering the delta will increase the already-rising salinity.

But water resource engineer Jay Lund of UC Davis says the increase in delta salt levels would be small. 

LUND: "In our modeling results, we're not seeing a tremendous effect.  We're seeing 1 percent or less effect on agricultural productivity."

Just how to restore the delta and still provide water to Californians is an ongoing question -- with more than ecosystems at stake.  The delta contains a network of 1,100 miles of levees that protect 4 million people and a $5 billion agriculture industry.