California is having the wrong debate about the future of one of its most valuable assets, the Sacramento-San Joaquin River Delta, which produces water for much of the state.

The battle for the better part of the last two years has been about how big a new conveyance system -- probably tunnels -- should be, how much it should cost, and who should foot the bill. The result has been a political fight of the worst kind, pitting Northern Californians against Southern Californians and agriculture interests against environmentalists. At its worst, this could be one of the biggest water grabs in state history. And for California, that's saying something.

 A ski boat heads west into the Sacramento-San Joaquin River Delta between Antioch and Stockton, Calif. (AP Photo/San Francisco Chronicle, Lance Iversen,
A ski boat heads west into the Sacramento-San Joaquin River Delta between Antioch and Stockton, Calif. (AP Photo/San Francisco Chronicle, Lance Iversen, File)

The focus instead should be the operating conditions for the Delta, particularly the amount of water that needs to flow through it annually to maintain the health of the estuary. Once that standard has been established, then everything else will fall into place for the two coequal goals of providing a more reliable water supply and protecting, restoring and improving the Delta ecosystem.

Before deciding on tunnels, helicopters, whatever, state water officials need to determine how much water can be expected to be delivered.

Why has the debate focused on the conveyance system instead of this basic question? Follow the money.

Central Valley agriculture interests and Southern California water districts are footing the bill for the Bay Delta Conservation Plan, basically the tunnel plan that is backed by Gov. Jerry Brown. The farmers and water users would pay for most of the $25 billion project, so they want to guarantee as large a reliable water supply as possible. The bigger the conveyance system, the more water it can carry, even though we don't yet know what taking that much water away will do to the Delta.

The plan's backers aren't interested in lesser alternatives, including the single-tunnel "Portfolio Alternative" backed by many members of Northern California's congressional delegation. Their solution would carry about a third as much water as the twin-tunnel plan.

The state Department of Water Resources suffered a major embarrassment on Nov. 12 when it admitted that as part of the BDCP process, it had overestimated the cost of that single-tunnel project by a whopping $3 billion. This cut the estimate by a quarter to $8.6 billion, a much greater saving from the $14.5 billion estimated for the two huge tunnels.

The admission calls into question the accuracy of the entire BDCP proposal, which has raised serious questions from economists and experienced California water experts about the cost benefits every step of the way.

Unless reliable answers are forthcoming soon, activists should stop bothering to ask the questions and begin fighting to stop what increasingly feels like the wrong plan for the Delta.