The Great Water Problem Simplified : The issue is this: More and more people, almost the same basic amount of water

California’s drought, now headed into a sixth year, may never end--at least not the way the state is growing. Population growth ensures that the demand for water will increase at a steeper incline than the supply.

This means the state has what is called a structural supply problem. So there is no room for slippage in Washington’s effort to rewrite federal water policy. Nor can Southern Californians read too much into moves by water managers to give them a slight breather from rationing in light of recent rains.

It is all wrapped up in a picture that can be drawn by the numbers--by some very big numbers. In a normal year, it takes nearly 5 million acre-feet of water a year to supply 15 million people. (A football field a foot deep in water would hold roughly an acre-foot, about enough to supply a family of five for a year.) In a dry year, with conservation measures, it takes 4 million acre-feet.

Such amounts include everything pumped from wells in Southern California and imported from the Owens Valley, the Colorado River and the Sacramento Delta by every delivery system built over the last nearly 100 years.

But 15 million also happens to be the number by which California’s population has grown just since 1960. There is neither money to build nor water to fill new delivery systems fast enough to keep up with growth.

There may be more water than money. Engineers designed the State Water Project to deliver 4 million acre-feet to cities and farms, but the uncompleted system delivers just half this; even 10 years ago, $23 billion would have been required to finish it--$11 billion for construction and $12 billion for interest.

Only one thing can overcome numbers like these. It is the bill now moving through the U.S. Senate Energy and Resources Committee that would allow a portion of the 8 million acre-feet of irrigation water delivered to the San Joaquin Valley each year to be sold to cities in dry years. This legislation is essential to California’s future.

Meantime, Southern California’s Metropolitan Water District plans to increase deliveries as much as recent rains allow, but only that much. The MWD will do no more than pass through those additional deliveries from the State Water Project that Sacramento thinks it can safely promise. That may be no more than a breather.

Even with normal rainfall for the rest of the year, northern rivers would remain sluggish by historical standards and 1992 would still qualify as a “critically dry year.” And Southern Californians would once more need to come close to their enviable record of cutting water use by as much as 30% in parts of the region.