Every day, Sacramento's wastewater treatment plant sends 13 tons of ammonia downstream to the Sacramento- San Joaquin Delta, potentially disturbing the Delta's food web in profound and destructive ways. Agricultural runoff flows freely through the estuary's waters. Exotic species of clams consume much of the critical food supply. Nonnative fish prey on native smelt and salmon.

Unchecked and unmanaged, these and other threats to the Delta's fisheries are tolerated on a regular basis. Yet, in an imbalance that grows greater with every passing month, the already heavily regulated water projects in the Delta - projects that supply water to millions of California residents, businesses and farmers - get hit with restriction after restriction on water flows.

It happened in November, when the California Fish and Game Commission made a decision that could drastically reduce water supplies in an attempt to protect a single species, the longfin smelt. It happened again this week, when the U.S. Fish and Wildlife Service imposed new restrictions - cutting up to half of the traditional water supplies in dry years - because of a different species, the Delta smelt. Come spring, still more restrictions may be looming for two different species of salmon.

The endless churn of bureaucracy and conflict surrounding the singular issue of water pumping is not creating a healthier Delta. Too many other stresses contributing to the Delta's decline have been left unaddressed.

As the recent special report in The Bee points out, the Delta is a unique, valuable and historically significant place - an ecological treasure chest and water hub in the heart of California. Clearly, this magnificent estuary deserves a more comprehensive and long-term approach to healing the fragile ecosystem while creating a more sensible and effective water system for the state.

Leading scientists, water providers, policy experts and environmentalists are working on just such an approach. Called the Bay Delta Conservation Plan,the effort is aimed at developing a new water conveyance system around the Delta that will separate and secure the movement of the fresh water supply while restoring habitat for the Delta's ailing fisheries. (To learn more about BDCP on the Internet, visit www.resources.ca.gov/bdcp).

The state and federal wildlife agencies responsible for the Delta are the ones who must ultimately approve this plan (the target date is the end of 2010) as meeting all the many environmental and water supply needs. The Legislature, in the meantime, could do the Delta a great service by reviewing the many other stresses to the Delta ecosystem, and taking decisive action.

Changing longstanding patterns is always difficult. Re-engineering a water system the size of California's certainly will be costly. And restoring health to the ecosystem will be an unprecedented balancing act.

But the future of California depends on such a comprehensive and sustainable approach to managing the natural resources of the Delta and the statewide water supply. Twenty-five million Californians in the East and South Bay, the Central Valley and Southern California need and deserve a reliable water source now and into the future. So do the countless businesses, industries and farmers who contribute to our economy and to our individual and collective well-being.

Until a new mind-set takes hold,we will continue a cycle of regulating that misses the mark. And we will continue living with the consequences. As Delta problems such as Sacramento's tons of daily wastewater pollution go unaddressed, farms south of the Delta are going without water because of water supply restrictions. And farm communities such as Mendota, in the heart of the San Joaquin Valley, are struggling.

There, the unemployment rate is approaching 40 percent. And the local food bank can't keep up with the demand and is turning away hungry families for the first time. Mendota's mayor, recently speaking to the press of the situation, said it best. "We're supposed to supply the world. And people are starving."

Laura King Moon is assistant general manager of State Water Contractors, a nonprofit association of 27 public agencies from Northern, Central and Southern California that purchase water under contract from the California State Water Project. For more information on the State Water Contractors, visit www.swc.org.