FROM a low-flying plane, the San Francisco Bay Delta is a shimmering sprawl of marshes, bogs, and tule swamps laced together by canals, levees, and flood plains.
More than 1,600 square miles stretching north and east of San Francisco, the unwieldy web of water is formed Medusa-like by the joining of the Golden State's two largest arteries: the Sacramento River, flowing south through the mammoth Sacramento Valley, and the San Joaquin River, flowing north from the equally gigantic San Joaquin Valley.
Seventy-five percent of the state's water cuts through this aquatic Grand Central Station en route to homes, industries, farms, cities, and environmental users. Together, 45 percent of the nation's produce comes from the two regions. They also harbor 120 species of fish, while serving as the drinking water source for 20 million (and soon to be millions more) Californians.
This year, after three decades of abuse, neglect, and decline in water quantity and quality, the Delta is facing a moment of truth. Because the state hasn't come up with standards ensuring ``fishable, swimmable waters'' - as called for in the Clean Water Act - and has been sued by 16 environmental groups for that failure, the Clinton administration is moving to promulgate its own standards.
``Of the West's many ongoing water wars, California's is the most complex and far-reaching in consequences,'' says Marc Reisner, author of ``Cadillac Desert,'' a classic on the West's water development. ``The Bay Delta is ground zero in that war.''
Salinity is the problem. When too much salt water from the Pacific Ocean backs up through the estuary's turns, fish are threatened, along with the commercial-fishing industry, drinking supplies, and water flowing to farms and cities as far south as Los Angeles. Fresh water that could hold off the Pacific backwash has, over decades, increasingly been siphoned off with devastating consequences.
Since 1969, winter-run chinook salmon have declined from 118,000 spawning fish to 341 in 1993. Delta smelt have declined 90 percent in 10 years, and striped bass are also down 90 percent, from the 3-million-to-5-million level of the 1970s. Water quality for drinking and agricultural use for the region's 200 crops is more at risk. Because of diversion, fresh-water flows to the Bay have been reduced by up to 60 percent.
In an unprecedented action by four federal agencies, new water-quality standards were announced Dec. 15 to reverse long-term environmental destruction of the region and the adjacent estuary stretching from San Francisco to Sacramento. If adopted, the standards will result in significant amounts of fresh water being diverted from cities and farms into the Delta, especially in dry years.
``Final adoption of [these] standards will be one of the most significant steps taken this century toward restoring the balance between agricultural, urban, and environmental needs,'' says David Behar, executive director of the Bay Institute of San Francisco, a nonprofit research and environmental-advocacy group.
The federal agencies - the National Marine Fisheries Service, the EPA, the Fish and Wildlife Service, and the Bureau of Reclamation - have worked for several years to come up with the standards. Known as ``Club Fed,'' they estimate that 500,000 acre feet of additional fresh water will be needed to run into the Delta each year, and as much as 1.1 million acre feet during droughts.
Since that is about 7 percent of the water drawn from the Delta, the idea is being called ``the Seven-Percent Solution.'' (One acre foot of water equals about 326,000 gallons - which would cover one acre of land, one foot deep, or enough water to serve a household of four for a year.)
The federal proposal designates minimum salinity standards for Suisun Bay, a fish nursery habitat area adjacent to the Delta, and reduced salinity for several tributaries in an effort to protect migrating chinook salmon and the spawning areas of striped bass. It proposes designating another fish - the Sacramento splittail, a 12-inch-long member of the minnow family - as a threatened species. And it upgrades the status of the winter-run chinook salmon from threatened to endangered.
Now, as with many junctures in state water history, a new fight has begun. But the clock is ticking.
Ninety days of public comment is expected to end by early April, and virtually every state water interest is marshaling forces to question, limit, offset, and change the standards in public hearings.
There is a political snarl added to the mix as well. Although the federal government has issued the standards, it is the state that has the jurisdiction to enforce them.
The hovering questions are how and whether the state will cooperate in shaping and carrying out the new rules.
``The draft water-quality standards for the ... Delta ... will thoughtlessly cost California jobs and fail to balance the compelling needs of urban, industrial, and agricultural users,'' Gov. Pete Wilson (R) says.
There is no national precedent for reconciling the requirements of state water-allocation laws ``with the sometimes conflicting and very stringent requirements of the federal Endangered Species Act,'' Governor Wilson says.
``It is my hope that the Clinton administration can help provide a federal-state forum in which these difficult issues can be discussed,'' he added.
David Kennedy, head of the state Department of Water Resources, says the standards will undoubtedly be changed in coming months, but for the first time in state history, the handwriting is on the wall: The state must deal with its damaged Delta.
``I don't think that any of the many interest groups in this matter have any interest in dragging this out anymore,'' Mr. Kennedy says. ``What is different now ... is that all the players are at the table with a commitment to work it out, rather than just review and stall.''
But reaction around the state is mixed. Though environmentalists have hailed the action as a milestone, urban and agricultural interests say the proposals are unrealistic.
``We have heard over and over that the feds are willing to accommodate and reduce the impact on the California water supply and economy while still protecting the Delta,'' says Duane Georgeson, assistant general manager of the Metropolitan Water District of Southern California. MWD and five other southern California water agencies have joined forces with five Bay-area agencies to question the base averages on which the EPA's salinity standards are measured. They also hold that the EPA's dry-year allotments could drain state reservoirs if measured against needs during the recent seven-year drought.
The California Farm Bureau Federation (CFBF) has also come out against the standards and will interject its concerns in coming talks.
``The problem is that the EPA does not have the responsibility to balance the needs of endangered species against the competing needs of people to live and eat,'' says Bill DuBois, a consultant and the CFBF's retired director of natural resources.
And Rich Golb, Northern California Water Association president, says if the new water needed for the Delta comes from the Sacramento Valley, new lawsuits may be pending. ``I don't think it's fair for anyone to ask northern California water users to help solve a problem they did not create,'' he says, noting scientific studies showing that 90 percent of the Delta's problems result from pumping water from the Delta to farms and cities in the south. The Sacramento Valley now contributes 5 million acre feet of water for state needs, and several state and federal laws prohibit the export of water not deemed a surplus in its area of origin.
``A lot of folks are viewing this as an illegal assault on California water law,'' Mr. Golb says. ``You have the federal government dictating to California how to use its most precious commodity. We feel that is wrong.''