A new multidisciplinary modeling effort concludes that certain tracts of land in California’s Sacramento Delta should be abandoned the next time they flood, and that major California water-supply inlets in the area should be rerouted. The study indicates the kind of land-preservation and infrastructure triage that will become increasingly necessary in the face of rising sea levels and climate change.

“It’s always difficult and controversial to look at these kinds of things,” says Jay Lund, a professor of environmental engineering at the University of California, Davis, who co-led the study. “For those delta landowners where the policy has been historically to help them–they would be losers. But I don’t see any way they are not going to be losers, so the state policy should be that we all quit losing.” This week, Lund spoke about the study at a California Energy Commission conference on climate-change research, held in Sacramento.

The Sacramento Delta is where the Sacramento and San Joaquin rivers converge with each other and meet incoming salt water from the San Francisco Bay. The area is a source of fresh water for agribusiness and more than 20 million Californians. Within the delta, tracts of land have been reclaimed over the past century, mostly for farming. Earthen levees–which, if put end to end, would stretch more than 1,000 miles–keep water-supply inlets fresh and reclaimed areas dry.

But a combination of settling land, rising sea levels, and the prospect of levee destruction from earthquakes have long threatened the area. In 2004, when a delta levee unexpectedly collapsed, the state and federal governments rushed in to repair it, spending more than $75 million. However, the effort protected land worth only $22 million. “Throwing a lot of money at a low-value private asset is not something you want to do with taxpayer money very often,” says Richard Howitt, an economist at UC Davis who participated in the study. “We wanted to put a lot of work into what really amounts to a triage list–and say which islands, if they collapse, we say, ‘Sorry about that,’ but you don’t repair them or pump them. You adjust to a new ecology.” (By “islands,” Howitt means low-lying tracts protected from surrounding water by levees.)

The study–which spanned disciplines including civil engineering, climate science, economics, hydrology, and biology–specifies a precise boundary between areas that should and shouldn’t be saved. It also recommends that long-considered plans to build a canal to divert water supplies from points upstream on the two rivers should be carried out now; the present inlet points cannot be protected from salt-water incursion in the long term. The canal proposal was defeated in a 1982 referendum, but ultimately, Lund says, some environmental concerns about the canal’s construction will be moot, because unstoppable salt-water incursions will reshape the area’s ecology. Indeed, the study notes that its recommendations for the delta are “one example of how climate-change will shake-up long-cherished notions of environmental management and sustainability.”

“Unless we get some serious modeling,” Lund adds, “we’re never going to get ahead of these changes. We’re just going to be reactive.”

The study even looked in detail at the effects of various topographical changes on fish and the resulting economic costs. “Fish biology is a very complex business, but we sat down with 37 fish biologists, bought them a nice lunch and quizzed them and got a proper statistical distribution of their beliefs of certain species’ surviving under certain scenarios, and came up with economic decision models,” Howitt says. “We are not the only ones doing this, but we are probably one of the more comprehensive. What we’ve done is quantitatively link the different disciplines.”

The analysis would seem to have sobering implications. In terms of sea-level rise, expensive infrastructure investments will have to be made–or willfully not made–in parts of New Orleans, the Everglades, Bangladesh, and the Netherlands, to name just a few obvious spots.

On a more subtle level, climate change will profoundly affect water supplies everywhere, because it will bring deeper droughts, changes in rainfall timing and intensity, and reduced mountain snowpack. “The critical issue is that it will change our planning paradigms, and it will change the information we use to make decisions,” says Richard Palmer, a civil engineer and water-resources expert at the University of Massachusetts, Amherst, who praised the California study. Planning appropriately to keep tap water flowing, Palmer says, will require more such studies that cross disciplines, drawing on climate and atmospheric science, hydrology, civil engineering, and economics.