Southern California's biggest water agencies are putting down roots in the Yolo Bypass.

The Metropolitan Water District of Southern California and Westlands Water District are buying land and jointly planning restoration projects in the bypass to protect their access to water from the Sacramento-San Joaquin Delta, officials told The Bee.

The agencies are the two largest diverters of Delta water, contributing to the decline of threatened Delta smelt and other fish. A related disruption of the Delta's food chain has prompted fears that an ecosystem collapse is under way, which could affect water quality for millions.

The water agencies hope to protect their diversions by creating more habitat for fish to thrive.

This new interest has local residents worried. They fear the water titans have other motives, such as draining groundwater from the area or somehow seizing Sacramento River water rights.

"The purchase of land by out-of-county water districts makes us nervous," said Yolo County Supervisor Mike McGowan. "Until we see some real legitimate response from these entities being willing to work with us, we'll continue to be paranoid about it."

The lower Yolo Bypass is considered a prime area for restoration because its elevation allows natural tides to sweep up the Sacramento River and over the land.

Breaching levees on farm parcels in the area would create more tidal wetlands, a type of habitat that could improve the fortunes of the smelt. The small fish may be near extinction after decades of water diversions and pollution in the estuary.

A panel appointed by Gov. Arnold Schwarzenegger last year declared that a healthy ecosystem and water supplies must become "co-equal values" in the Delta.

Roger Patterson, assistant general manager of the Metropolitan Water District, said his agency heard that message.

"As we look to improve our water supply situation, we know that is directly tied to the ecosystem," said Patterson, whose agency provides water to 18 million people in Los Angeles and San Diego. "So we need to start making smart investments in the ecosystem if we're going to see these co-equal goals advance together."

Metropolitan, Patterson said, is looking to buy land in the bypass for restoration and also seeking opportunities to partner with other landowners for that purpose.

He and Tom Birmingham, general manager of the Westlands Water District, said they need to move fast because their Delta water supply has become tenuous.

A federal judge in Fresno last year ruled that state and federal water export systems in the Delta violated the Endangered Species Act. Water supplies were curtailed this year as a result.

The judge ordered new permanent operating rules for the pumping systems. This may bring lasting water cutbacks for Westlands and Metropolitan, and they may be required to pay for habitat restoration to retain access to Delta water.

As a result, the agencies say they can't wait for state and federal governments to launch restoration projects. As evidence, they point to the failed plan for a North Delta Wildlife Refuge. Proposed in the lower bypass in the late 1990s, it was never funded by Congress.

Westlands is the world's largest irrigation district, serving about 600,000 acres of farmland in Fresno County.

"There certainly is an urgency because the Delta is broken, and we have species that are on the verge of extinction," said Birmingham. "Our ability to move water through the Delta is going to depend on the health of these species."

In December, Westlands made the first leap into the bypass by purchasing a 3,400-acre parcel called Yolo Ranch from the McCormack family.

The property is adjacent to three parcels of government or nonprofit-owned land totalling about 8,000 acres. All are well-situated to become tidal habitat.

Westlands has since been approached by other property owners offering to sell land, Birmingham said.

Both he and Patterson insist their only interest is restoration.

"We want you to know we're there in good faith," said Patterson. "We're not coming and just saying, 'Well, what's for sale?' "

Other potential conflicts include preserving flood-control functions in the bypass. Water quality is another: Restoring tidal action could release contaminants from the land into the river.

To mediate these concerns, the Center for Collaborative Policy at California State University, Sacramento, recently launched the Lower Yolo Bypass Planning Forum. Sponsors include the state Department of Fish and Game, the Yolo Basin Foundation and the Delta Protection Commission.

The yearlong series of public meetings, starting later this month, involves some two-dozen landowners and government agencies. The goal is collaborative land management to improve habitat while preserving other values, including recreation, agriculture and peace between neighbors.

Westlands and Metropolitan will be full participants.

Call The Bee's Matt Weiser, (916) 321-1264.