The U.S. Army Corps of Engineers is facing a real-world "Mission: Impossible."

So says a National Research Council panel, which warns in a report today that the corps is being asked to tackle a growing list of complicated problems for managing water resources problems with a shrinking budget.

The corps' plight, the report says, reflects the fundamental "paradox" of U.S. water management.

"It's not just up to the corps to change themselves," said David Dzombak, an engineering professor at Carnegie Mellon University and the panel's chairman. "But the nation needs to rethink how we go about developing, prioritizing and implementing water resources projects."

The Army Corps' mission was long focused on harnessing water by building dams, levees and navigation channels, the scientists note. But in the last two decades, Congress has shifted the corps away from building big civil works projects to rehabilitating old ones, allocating limited water supplies to competing users and repairing ecosystems.

So the corps asked the research council to convene a committee to offer advice on how the agency might function with so many often-competing objections. The report released today is the first of five that will examine aspects of the agency's annual $5 billion water resources program. The council works under the umbrellas of the National Academy of Sciences and the National Academy of Engineering as a private, nonprofit government adviser.

"We're trying to take stock of the current situation and look at the future," Dzombak said.

The report's bottom line: The Army Corps' mission is unsustainable.

Congress has consistently opted to delay maintenance on the vast network of levees, dams and waterways, while adding new water projects to its wish list -- including home-state pork projects authorized under the banner of job creation and economic development, the report says.

In 2007, the report notes, the Senate approved a $14 billion list of water projects for the Water Resources Development Act reauthorization in May. But a reconciliation with the House yielded a $23 billion authorization with enough congressional support to override President George W. Bush's veto and become law.

Most of those projects have yet to get funding, the report says, offering an example of how lawmakers' desires have outpaced their ability to pay. The result: a $59.6 billion backlog in authorized projects and billions more in unmet maintenance needs, the report says.

"The collective backlog of unfinished work leads to projects being delayed, conducted in start-stop manner, and to overall inefficient project delivery," the report says.

As authorized projects get added to the corps' to-do list, the number of agency employees available to do that work has declined.

The corps' Civil Works Program, which manages water resources, has seen a more than 30 percent decline in staffing from a 1983 peak of 32,408 employees to 22,607 last year. The total number of employees throughout the corps declined 27 percent from a 1983 peak of 46,130 to 33,750 last year.

"This situation leads to expectations that the Corps of Engineers and its civil works construction program cannot meet consistently," the report states.

The Army Corps declined to respond to a request for comment on the report.

Modern efforts to manage water resources will only become more complex, the report says, inevitably requiring the Army Corps to work with smaller staff and budgets and to consider a wider range of environmental goals.

"The challenges the Corps is facing are fairly similar to the challenges that our nation is facing in infrastructure in general: The requirements are growing, the demands are growing, yet the resources and investment from whatever sources they need it to come aren't keeping up," said Rick Capka, chief operating officer of the water resources lobbying firm Dawson & Associates and a former Army Corps division commander. "Consequently, we're seeing things start to fray at the edges."

The Army Corps will also have to consult with a large number of stakeholders, in part because the 1986 Water Resources Development Act requires local governments and other project co-sponsors to help foot the bill. That has forced the corps to focus on local demands, sometimes at the expense of more comprehensive planning, the report says.

The implications, the report says, is that "the nation may have to consider more flexible, innovative, and lower cost solutions to achieving water-related objectives."

Missouri River

The report singles out as an example of the corps' dilemma the Missouri River, where the agency built six major dams in the 1930s and '40s that it now operates and maintains.

The corps must balance an array of competing needs on the Missouri: flood control, navigation, water supply, hydropower generation, recreation and wildlife.

The demands have grown as environmental laws -- the National Environmental Policy Act, the Clean Water Act and the Endangered Species Act -- have hit the books, the report says. Those laws are enforced by other federal agencies.

Balancing those duties against the wants and needs of states, local authorities, American Indian tribes, companies and residents who use the river and facilities became increasingly complex and burdensome, as the then-commanding general of the corps' Northwestern Division, David Fastabend, described in 2002 comments that the report cites.

"The challenge is that the people of the United States have -- over time -- told us to do many, many things," Fastabend said. "As you can well imagine, no one was able to 'deconflict' the multiple instructions given to the U.S. Army Corps of Engineers. Our guidance is sometimes contradictory, and the resolution of those contradictions is extremely problematic."