On a dry day in June 2004, one of the many levees that define the geography of the Delta gave way. Water flooded 12,000 acres of the Jones tract and forced water managers to shut down pumps to prevent brackish water from being sucked into the water supply for millions of Californians. The damage was $100 million.

If that were not warning enough that the intricate system of levees is at risk, Hurricane Katrina certainly was. It battered the Mississippi Delta, breaching levees and flooding New Orleans. Like New Orleans, much of the land in our Delta is below sea level and held back by levees of questionable stability.

Fortunately, unlike New Orleans, the Delta is sparsely populated. But that is rapidly changing as thousands of homes are being build on islands that are flood risks.

One has to wonder if a levee can collapse on a sunny day, what could happen if there were a series of wet winter storms or, even worse, if there were a major earthquake. Both earthquakes and excessively wet winters are hardly remote threats. It is just a matter of time before the Delta is saturated and/or shaken and one or perhaps several levees fail.

Should just a few levees break, the impact could be significant, running into the billions of dollars in damage. Despite this very real threat, CalFed, the consortium of various water interests, has done virtually nothing to avert a potential disaster even though levee protection was one of the organization's primary goals. There is no plan in place to deal with weakening levees that rest on soft peat. Some were first built more than a century ago and are vulnerable even though they have been widened. Over the years, the foundations weaken as the land they protect gradually subsides. More pressure is placed on the levees making them less stable. The effect of sinking land on aging levees has long been known. Yet there has been no accurate assessment of how weak the levees are, much less a plan to fortify them.

The Delta does not yet have a large population, but it is critical to water supplies for 23 million Californians, and is traversed by natural gas pipelines and power transmission lines. CalFed must get on the job now to assess the risk to the Delta levees and devise a workable plan to prevent a major catastrophe to much of the state's water supply and economy.