Governor Edmund Brown has proposed 40ft (12.1m) inside diameter tunnels built more than 150ft (45.7m) underground, along with water intakes and habitat restoration to reverse the decline of native fish populations in the Delta and provide reliable water delivery for two-thirds of California¹s population and much of the state¹s agricultural economy.

The full plan will be released in three stages over the coming weeks, and an accompanying Draft Environmental Impact Statement/Environmental Impact Report will be released for formal public comment later this year.

The newly-released chapters detail the proposed operation of a new system of pumping plants and tunnels to carry water from the Delta. A new water project diversion point on the Sacramento River near Sacramento and 35 miles of TBM-driven tunnels would secure water deliveries against catastrophe.

³At any time, a flood or earthquake could inundate the below-sea level islands in the interior Delta and draw salt water toward the existing south Delta pumping plants, which would have to be shut down to avoid contamination,² according the agency.

Additionally, water deliveries to the Bay Area, San Joaquin Valley, and Southern California have been reduced in recent years in part because of the presence of federally protected salmon and smelt near the existing water pumps in the south Delta.

Last July, Governor Brown, joined by Secretary of the Interior Ken Salazar, announced revisions to the plan, including a 40 per cent reduction in the capacity of proposed new water diversion intakes along the Sacramento River. The Obama administration has been working with state agencies to assist in developing a plan that will meet legal requirements and allow for appropriate integration with the federal Central Valley Project.

"We are making real progress," said California Department of Water Resources director Mark Cowin. "Getting to this point has been a long, complicated journey, but we have worked through some truly difficult issues. We are now closer than ever to finally safeguarding a water supply critical to California’s future and restoring vitality and resiliency to the Delta ecosystem."