SACRAMENTO - -- Gov. Jerry Brown and U.S. Interior Secretary Ken Salazar are set to announce Wednesday plans to build a massive twin tunnel system to carry water from the Sacramento-San Joaquin River Delta to farmland and cities.

Officials say the $23.7 billion proposal includes over 100,000 acres of floodplains and tidal marsh habitat restoration.

Tunnel construction itself would cost about $14 billion and would be paid by water users. Officials say taxpayers would bear the $10 billion cost of habitat restoration, but a water bond that could provide some money for restoration was moved to November 2014.

The tunnel proposal is facing stiff opposition from delta residents, some environmental groups and Northern California legislators.

Supporters say the tunnels will guarantee a stable water supply, improve water quality and help protect the state's water delivery system from earthquakes.

State officials admit they don't know just how much water would be diverted through the tunnels or how habitat restoration and decreased flows would affect the fish. They say these questions would be answered through scientific studies that accompany construction over the next 10-15 years.

But opponents argue it would devastate the delta region, including its ecosystem and agriculture-based economy. They say it's unacceptable to proceed with building the tunnels without knowing up front their impact on imperiled fish species such as salmon and smelt.

The amount of water to be pumped would depend on what is good for the fish, said Karla Nemeth, program manager for the plan at the California Natural Resources Agency.

Formed by the confluence of California's two longest rivers -- the Sacramento and the San Joaquin -- the delta supplies drinking water for two-thirds of Californians and irrigates nearly 4 million acres of farmland.

The ecosystem's rapid deterioration and the crash of once-abundant fish populations a decade ago has spurred regulations that limit delta pumping, especially during dry years. Farmers in the Central Valley say the restrictions have forced them to fallow productive land.


Wozniacka reported from Fresno, Calif.