WASHINGTON – An ambitious draft plan to protect California's crucial Bay-Delta region while guaranteeing farm and urban water deliveries is fragmented, incomplete and hard to understand, a National Academy of Sciences panel warned Thursday.

In a stern midcourse review, independent scientists said the nearly $150 million spent so far hasn't yet bought an effective playbook for meeting the dual goals of providing water and preserving the Sacramento-San Joaquin Delta.

"Given the time and expenditure of money, people could have reasonably expected to get a plan that was more complete," said Henry Vaux Jr., an emeritus University of California, Berkeley, professor who chaired the panel.

Significantly, the scientists also warn that current Bay-Delta planning may assume too much about a proposed tunnel or canal to divert the Sacramento River around the Delta.

State and federal officials largely accepted the criticisms but stressed their progress since the release of November's draft plan, which the scientists reviewed.

"It only represents a snapshot of where this process was seven months ago," said California Natural Resources Secretary John Laird.

David Hayes, a deputy Interior secretary and the Obama administration's point person for California water, agreed that "much additional work" is being done.

"We are midstream," Hayes said, stressing that officials will "move toward a much more mature draft" in coming months.

California water districts initiated Bay-Delta planning in 2006, hoping to swap environmental protections for more reliable water supplies. The plan, due in 2013, will specify how to protect habitat and species while delivering water to cities and Central Valley farms for the next 50 years.

The draft plan spanned more than 1,100 pages.

But for all the bustle, the new panel of independent scientists determined that the draft is "incomplete in a number of important areas," suffers from a "lack of clarity" and overall has some major shortcomings.

"The purposes and goals of the plan are unclear," Vaux said Thursday, adding that otherwise solid scientific work "has not been knit together" coherently.

The study overseen by Vaux and 12 other scientists was organized through the National Academy of Sciences' National Research Council. Though it's severe, some hope it could help slap California water planning into shape.

The plan "must be based on sound science and a thorough review of the alternatives, and we welcome input like this that will bolster the chances of success," said Cynthia Koehler, senior attorney with the Environmental Defense Fund.

The Bay Delta Conservation Plan is a written document, a negotiating process and a set of political rapids all in one. The joint state and federal effort must balance multiple goals that include protecting the Delta estuary, keeping tiny smelt away from pumping plants and ensuring reliable water supplies for the 25 million Californians who depend on the troubled Delta.

More than 90 percent of the original Delta habitat has been lost. Intruding salt water threatens what remains. Native fish populations are at or near record low levels.

Farmers, meanwhile, face fluctuating water supplies and perennial uncertainty.

The independent scientists stressed that the Bay-Delta planning fails to assess alternatives to the Delta tunnel or canal option.

The plan assumes that the conveyance system might carry up to 15,000 cubic feet per second, on roughly a 45-mile route around the Delta. The new study suggests that this incorrectly assumes that farms south of the Delta will continue to use as much irrigation water as they are now.

Hayes insisted that no one has "prejudged" the merits of a Delta conveyance system.

© Copyright The Sacramento Bee. All rights reserved.

• Read more articles by Michael Doyle

Order Reprint