The federal government, after spending $30 billion on the country's largest public works program in recent history, still has no reliable way to measure the impact of thousands of modern sewage treatment plants on national water quality.

The absence of accountability in a program that represents the country's front-line defense against water pollution is startling, and revolves around a fundamental question: is the water any cleaner?

The Environmental Protection Agency doesn't know. The U.S. Geological Survey doesn't know. The top water quality experts in the country don't know. Most of all, Congress, which has spent the $30 billion, doesn't know.

What little information exists suggests that there has been little or no change in basic water quality since 1972, when Congress made a major commitment to fund the sewer grants program through the EPA.

Congress and the EPA have spent huge sums on costly waste water treatment plants, most of which don't operate properly and a third of which seriously violate pollution laws.

The public relations of the past decade have made it a forgone conclusion to most Americans that the nation's water supplies were once seriously polluted, but that they are much better today due to the enforcement efforts of the EPA against industry, and congressional spending to aid a clean up by the cities.

There are, in fact, some notable improvements, success stories such as the Houston Ship Channel, Oregon's Willamette River and Cleveland's Cuyahoga River.

And obviously, new sewage treatment plants, assuming they work right, do some good in their localities. Fishermen who are catching game fish where there were none are convinced of real progress.

And yet few experts are willing to say that, overall, the water quality in America's lakes and rivers has improved substantially.

Certainly, there is no evidence that the $30 billion grants program for waste water treatment has helped measurably.

Part of the uncertainty is expressed in a new General Accounting Office report concluding that the nationwide network for monitoring water quality operated by the EPA and the Geological Survey produces data that are "not reliable."

"Water quality is far too complex to be monitored by these networks," the study concludes, adding that it is fallacious for the EPA and other agencies to make broad judgments about the quality of all surface waters in the United States based on irregular samples at fewer than 2,000 monitoring stations.

A leading water quality consultant, Jerome Horowitz, who contributed to the GAO report, said that it spotlights the "pointlessness of attempting to assess the immense water resources of the nation from a few hundred buckets of water a month."

The report criticizes widespread scientific sloppiness in the way tests are performed on water samples. Tests on identical samples provided to different laboratories routinely gave widely varying results, the report found. In addition, many tests are rendered useless because many water samples were not analyzed before they went stale.

In addition, the report says that the chemistry of rivers and streams can be affected dramatically by the seasons, spring floods and summer droughts, daily cycles of high and low oxygen content that support fish life, and dozens of other factors.

Thus, it adds, the current haphazard system of monitoring cannot adequately assess the impact of sewage pollutants on this complex chemistry.

As a result the GAO recommends that the EPA and the Geological Survey abandon the network of monitoring stations and concentrate on intense, roving studies if individual streams and lakes.

Even with the current network data, the president's Council on Environmental Quality concluded in its most recent annual report that ". . . the quality of surface water nationally has not changed much in the last five years."

More specifically, the report noted that the level of toxic substances in most rivers and lakes is still not known. ". . . The lack of monitoring data for most toxic substances makes it impossible to estimate how widespread the problems are or to say whether conditions are improving or deteriorating."

And, because EPA had focused most attention on water quality in rivers, "lake water quality has received relatively little attention . . . very little systematic monitoring has been done. Consequently, there are no national data for the study of trends."

Other water quality experts agree with the report and say it would take a significant national expenditure to study the natural chemistry of lakes and rivers and then to monitor the impact from municipal and industrial wastes.

President Johnson's water quality expert, Joe G. Moore Jr., pointed out in an interview that the $30 billion investment in wastewater treatment plants has resulted in completion of only about 2,000 of the 18,000 plants planned. And most of the plants are small ones.

"What I'm saying is that there has not been sufficient time . . .[for] a major impact to have been felt in water quality.

"A lot of medium and small plants have been built across the country, and chances are they will have produced improved water quality in the immediate area of discharge," he added. "It has been nothing like the progress which was intended to be made under the 1972 [clean Water] Act."

Horowitz, the independent consultant whose stinging reports over 10 years have pinpointed serious flaws in the EPA's effectiveness and planning, maintains that it is impossible to make even the most general statement about national water quality due to the lack of reliable data.

"Has the [EPA] construction grants program made any great difference on water quality? I can't tell," he said in an interview.

The EPA is not without some tools of measurement. Each municipality that discharges waste water is issued a permit setting limits on the levels of pollutants discharged. But these permits attempt only to regulate what goes into the water, and tell nothing about water quality.

Moreover, the EPA's studies, as well as those of GAO, show that more than half, and perhaps nearly 90 percent, of the new generation of treatment plants are violating discharge limits.

What the government has learned the hard way is that the overblown goals and generously funded solutions of the 1960s and 1970s are producing a failure in the 1980s.

Experts and politicians agree that the federal commitment to clean water is a noble venture and one that can continue if the government planners and legislators are willing to ask hard questions about the premises.

"The height of water wisdom has not been in the past, hopefully it will be in the future," said Larry Silverman, whose Clean Water Action Project was one of the biggest promoters of the grants program.

The program's failure, however, will certainly fuel criticism from conservatives bent on getting the federal government off the backs of local governments and out of the taxpayers' wallets. But a wholesale bureaucratic slaughter at the EPA by the new Reagan budget-cutters will still leave the country with a need to protect the quality of its waterways.

Like many programs of the early 1970s, the clean water program is big, but is bigness has not caused it to founder.

Among the greatest deterrents to the program's success were the political concessions of its creators, who tried to make it all things to all people.

This flaw illustrates one of the principal tensions of Congress: can the national legislature confront a large national problem and tailor a solution that does not succumb to the pork-barrel temptation of spreading the money around the country, often at the expense of efficiency and success?

If there is any wisdom to be derived from the current troubled program it is that in the future Congress might want to understand the dimensions of the pollution menace better before it declares war on it.

Leaders of the environenter before it declares war on it.

Leaders of the environmental movement of the 1960s and 1970s were the first to raise the national alarms over water pollution. They seized the opportunity, molded a powerful national constituency and won spending commitments of magnitude seldom achievable in the give-and-take of national priorities.

Yet at the time, the science of how pollutants affect water was in its infancy, and is still largely undeveloped. How rapidly are pollutants assimilated by a given body of water or stream? How do agricultural runoff, climate and seasonal changes affect water purity? These questions are largely unanswered.

Public reaction to stories of fish kills, rivers catching fire and wildlife choked by waterborne chemicals spurred Congress to throw billions into the water pollution war using the latest technological solutions, all based on a paucity of knowledge and, in many cases, the absence of sound judgment.

By blindly charging forward with generous funding for advanced waste water treatment plants, the public has paid the bill for multimillion-dollar facilities that may not be needed.

Solutions to the sewage pollution problem should not be biased in favor of high technology, engineering complexity or the greatest cost, many experts now say.

Silverman's clean water project has been preaching a return to "land applications" for sewage, like that now employed in Greenville, Maine, where city officials are spraying waste water on their Christmas tree crop.

EPA regulation and its rigid administration of the grants program has soured thousands of local officials on what began as a well-intentioned federal assistance program. A lot of pain and fiscal hemorrhaging has resulted from endless EPA "reviews" that contribute little and stretch out construction times at substantial additional cost.

Local officials say they want flexible national standards from EPA, not unreasonably rigid ones. Instead of setting secondary treatment as a national mandate for all municipalities, EPA should have paid attention to local conditions, they say.

Small communities at oceanside like Skayway, Alaska, should not automatically be held, perhaps, to the same treatment standard as large inland cities that discharge waste water into small fresh water streams or lakes.

Likewise, large cities that discharge into rivers heavily saturated with agricultural runoff, like the Missouri and Mississippi at St. Louis, should not automatically be held to the same standard of treatment as cities that discharge into high-quality streams.

And, many local officials would be thankful if Congress enforced its original order to EPA to keep rules and regulations to a minimum and to write them in clear and simple language.

On the other hand, the 10-year history of this program suggests that the Reagan administration will invite scandals if it walks away from the federal obligation to enforce standards and supervise the spending of federal dollars for clean water.

Many of the local scandals which have attended this program were the result of inadequate federal auditing and inspection as well as inflexible administration.

In the end, Congress may want to reexamine some of the basic premises on which the clean water program has operated in its first decade. Is it reasonable, for instance, to insist as a matter of national policy that the Mississippi River be "fishable" and "swimmable" at St. Louis, at New Orleans?

A pristine river in a heavily populated urban area may be achievable, but at a cost so great that taxpayers will choke. u

Or is it more likely that hard choices must now be made to salvage this program under a philosophy more akin to the times? In an era of austerity, the Reagan administration and Congress will surely balk at funding the $100 billion estimate for bringing the nation into compliance with the current Clean Water Act.

"Who really needs it the most?" will be the most pressing policy question of the 1980s.