For many months, we've held off on using the term "tunnel vision" to describe the Bay Delta Conservation Plan. It seemed too easy.

But there's no getting around the fact that, during most of its life, this planning process for the Sacramento-San Joaquin Delta has been inordinately focused on building a canal or a tunnel to convey extra water supplies to water contractors funding the effort. That type of tunnel vision has now come under withering criticism from the National Research Council, the research arm of the National Academy of Sciences.

In an 81-page report released last week, the NRC hammered Bay-Delta planners for "putting the cart before the horse" in rushing toward selection of a conveyance option before it conducted a full "effects analysis" on a tunnel and other alternatives.

"If the BDCP were largely a broader conservation program, designed to protect the ecosystem and provide a reliable water supply, then a more logical sequence would be to choose alternative projects or operating regimes only after the effects analysis was complete," the report said.

On Tuesday, Gov. Jerry Brown's top water official told lawmakers that a giant tunnel is no longer the state's leading option for the Delta.

"If you pre-commit to a project, you're going to fail in the (environmental) process, and we're not going to do that," said Jerry Meral, deputy secretary of the state's Natural Resources Agency.

Meral is sure to feel some heat for taking a more neutral stance on a Delta tunnel, but he needed to do so. Earlier this year, he seemed to suggest that a tunnel was a done deal, telling the Contra Costa Times that "something like a facility roughly of the size in the earlier documents will be proposed, will be permitted and be built."

Since then, state and federal officials have worked to rebuild trust in the Bay-Delta plan and make it more inclusive. Yet water exporters – who have put $150 million into a process now deemed as deeply flawed – are still operating under the assumption a tunnel will be built, and that it will provide them with extra water. Managing those expectations will be a major challenge for the Brown administration.

Given the realities of climate change and the chance that the Delta's levees could be damaged by earthquakes or floods (or both at the same time), there's a real need to study new conveyance options. Properly sized and managed, new plumbing holds the potential to more easily move water around the Delta, with fewer conflicts that now pit fish against water pumps.

Yet there are big questions that state and federal officials must resolve before any option is selected:

• Will BDCP result in a significant increase in water exports? Exporters expect it to do so, but some lawmakers say they did not sanction such a boost through the water reform laws of 2009. Conflict over this issue rose again Tuesday in the Assembly Water, Parks and Wildlife Committee between Tim Quinn, director of the Association of California Water Agencies, and Assemblyman Jared Huffman, D-San Rafael.

• What will be the impact on salmon and other fish? A canal or tunnel might improve conditions for Delta smelt in the south Delta, but to the detriment of salmon in the north Delta. The potential tradeoffs need to be fully understood before any option is selected.

• How much will a tunnel, canal or pipeline cost? The price would vary on size of the project, and the degree it would be used for "big gulps" (taking large amount of water during the wettest years) or continuous gulps. Yet at some point soon, contractors and policymakers need to know the costs and benefits of various options, so the discussion can begin on whether any of them are economically viable.

These are just some of the issues hanging over the BDCP. It's frustrating that more of them haven't been resolved. Yet it is too early to throw in the towel. The alternative – another round of legal water wars – is in no one's interest.

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