One of the nation's largest environmental groups has decided to support building a controversial new water canal around the Sacramento-San Joaquin Delta.

In a statement expected today, the Nature Conservancy calls a canal diverting the Sacramento River around the Delta an "essential component" to restore the estuary and protect water supplies. It thus becomes the first major environmental group to publicly support the project.

But the conservancy wants a new and independent governing agency formed first, to ensure that the canal is operated both to enhance the environment and protect water supplies. Resolving such thorny issues is why the group chose to express conditional support for the canal now.

"We need to explore something that's new and has more independence, and we need to do that as soon as possible," said Anthony Saracino, the conservancy's California water program director. "The trick really isn't in the engineering; it's in the governance."

This conflicts with Schwarzenegger administration officials, who on Friday opted to spend another year debating governance while planning to start canal construction in 2011.

It also left other environmental groups puzzling over the announcement.

Unlike the debate in 1982, when voters rejected the so-called "peripheral canal," many environmental groups today acknowledge a canal may be an effective solution to the Delta's troubles. But other issues must be resolved first, they say, including operating rules to protect the environment and an independent agency to enforce those rules.

"They've stated the obvious – that a canal that works for the environment would be acceptable to a wide number of groups," said Laura Harnish, deputy regional director of Environmental Defense. "The problem is, nobody's demonstrated how we do that."

Harnish's group and the Nature Conservancy are both part of a coalition of green groups working with state and federal agencies to develop a habitat conservation plan for the Delta. They have stated within that context that a canal is a promising solution – if it can be operated to improve the environment.

But until now, none has been willing to publicly announce support for a canal under any terms.

"They are the first ones out of the box to say 'Yes, this is a good thing, and we need to start talking about how to do it,' " said Laura King-Moon, assistant general manager of the State Water Contractors, who formerly worked for the Natural Resources Defense Council for 17 years. "It breaks the ice, and I think that's very helpful."

The water contractors, however, disagree that new governance is needed. They want to see Delta operations remain in the hands of existing agencies.

The Nature Conservancy is unique compared with other environmental groups, because it also owns huge tracts of land in the Delta: 9,000-acre Staten Island and 1,600-acre McCormack-Williamson Tract.

Both are managed for farming and wildlife habitat, and both were purchased, in part, with state grants.

Saracino also was once partners in a consulting business with Lester Snow, now director of the state Department of Water Resources. And his wife was once DWR's general counsel and chief deputy director.

He said none of these relationships influenced the Nature Conservancy's Delta policies.

"Even in business, Lester and I didn't always agree, and that continues. We're doing this because we hope we can move the discussion forward."

The conservancy's land could be dramatically altered by the state's "dual conveyance" canal plan.

The plan includes both an isolated canal around the Delta and a "through-Delta" canal built by bolstering existing levees. The preliminary route would follow the south fork of the Mokelumne River, which weaves along one side of Staten Island.

An initial Water Resources study last year states that the Mokelumne River's south fork would be dredged for the project. New levees, much wider and taller than those in place now, would be built to widen the channel.

This could take hundreds of acres of farmland out of production and eliminate habitat that exists now.

"It's not something we're terribly concerned about right now, in part because there's so many details still to work out," said conservancy spokeswoman Shari Cravens.

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