The National Academy of Sciences, sharply undercutting the Reagan administration's position on acid rain, said yesterday that there is a direct link between the sulfur dioxide spewing from industrial smokestacks and the death of aquatic life in lakes and streams of the United States and Canada.

The academy's finding of a proportional, one-on-one relationship between sulfur dioxide emissions and the phenomenon of acid rain was immediately hailed by environmentalists, who said it shreds President Reagan's argument that not enough is known about acid rain to warrant expensive new curbs on sulfur dioxide emissions.

"This report effectively concludes the scientific debate," said Richard E. Ayres, chairman of the National Clean Air Coalition, an umbrella group of environmental, health, labor and religious groups. "The academy's judgment is clear. Control at the source will work and it ought to begin."

The report also was welcomed by Canadian officials, who have pressed the administration to impose new controls on U.S. emissions in an effort to halt the mounting acid rain damage in eastern Canada, where dozens of lakes are completely dead and hundreds more are dying.

"The report has finally put to rest the notion that what goes up perhaps doesn't altogether come down," said George Rejhon, environmental counselor to the Canadian Embassy in Washington.

But the academy's conclusion brought anguished cries from the Midwest, home of the coal-fed power plants that are the nation's biggest source of sulfur dioxide emissions. It also brought a sharp rebuttal from the coal industry, which sees a crackdown on acid rain as a threat to the high-sulfur coal fields of the Ohio Valley. Despite mounting pressure from Canada, conservationists and Congress--where acid rain control bills are pending in both the House and the Senate--the administration has resisted pressure for tighter pollution controls, contending that scientists could not guarantee that cutting emissions would ease the problem enough to make it worth the money. Instead, the administration has called for additional research.

That position has been under review since William D. Ruckelshaus took over as head of the Environmental Protection Agency a month ago, but yesterday Ruckelshaus said that the newly released study does not necessarily mean the administration should take immediate action on acid rain.

"Understanding the nature of the problem and deciding what to do about it are two different things," he said.

However, a panel appointed by Reagan's science adviser reported earlier this week that the environmental risks were so great that a solution must be found despite the scientific uncertainties.

Yesterday's report goes one step further, saying that while researchers cannot identify which specific smokestack contributes to which dying lake, it is reasonably certain that a 50 percent reduction in sulfur dioxide emissions will yield the same reduction in acid rainfall.

The panel appointed by the White House suggested "economically efficient" steps to cut sulfur dioxide emissions, such as washing coal in a chemical bath to reduce its sulfur content. More expensive options include switching to low-sulfur coal or alternate fuels, or fitting smokestacks with "scrubbers" to remove sulfur.

None of the methods is cheap, however, and scientists who worked on the academy report firmly declined to suggest how government policy-makers should put their findings into practice.

But the chairman of the group, Dr. J.G. Calvert, an atmospheric scientist with the National Center for Atmospheric Research in Boulder, Colo., said the conclusion should reassure lawmakers and government officials "that they can get something for their bucks. It is a help to know that if we cut back anywhere we're gong to get a benefit from it."

Acid rain is the term applied to acidic compounds formed when airborne pollutants, chiefly sulfur dioxide (a byproduct of burning coal) and nitrogen oxide (which comes mainly from cars), are changed chemically in the atmosphere and come to earth as dry particles or mixed in rain and snow.

The phenomenon is blamed for severe environmental damage in eastern Canada and the northeastern United States, where some lakes and streams have been stripped of aquatic life. Recent studies have suggested that acid rain may be linked to forest damage, and scientists also are concerned that the acids may free metals in lake and stream sediments, posing a potential threat to drinking water supplies.

In its report yesterday, the academy discounted the effects of nitrogen oxides.

Canadian officials blame sulfur dioxide emissions from the coal-burning power plants of the midwestern United States for much of their acid rain damage.

But Carl E. Bagge, president of the National Coal Association, noted that the scientists could not determine the specific contribution of one area's pollution to another area's environmental damage. "In plain English, scientists can't yet determine the relative importance of midwestern emissions to rainfall in the sensitive areas of the Northeast," Bagge said.

"While this report will be touted as justifying proposed acid rain measures, it actually exposes the Achilles' heel of the current politically based bills," he said.

In anticipation of the academy's report, the electric power industry fired its round Tuesday, warning that congressional strategies that focus on the sulfur-emitters of the Midwest will raise electricity rates in some areas by as much as 50 percent.

While several government studies have rebutted the industry's rate figures, the economic arguments of the administration and industry have been persuasive in the last two years, especially among coal-state legislators who envision a disaster in high-sulfur coal markets.

The concerns have effectively frozen the Clean Air Act in its tracks. But congressional sponsors of acid rain legislation said yesterday they expect the new report to put some steam behind their bills.

"I believe that the academy study will give us a tremendous amount of momentum to pass acid rain control legislation by the end of the year," said Rep. Henry A. Waxman (D-Calif.), who with Rep. Gerry E. Sikorski (D-Minn.) has introduced a bill that would force gradual nationwide reductions of sulfur dioxide of more than 50 percent.

A similar but less sweeping proposal, involving only the 31 states bordering or east of the Mississippi River, already has been approved by the Senate Environment and Public Works Committee. Chairman Robert T. Stafford (R-Vt.), a cosponsor of that bill, said he was "more and more optimistic" that acid rain control measures would be included in a reauthorization of the Clean Air Act this year.

Environmentalists cite other positive signs as well, including Secretary of State George P. Shultz's apparent interest in resolving acid rain as a foreign policy problem between the United States and Canada.

The report released yesterday was a follow-up to an academy study released in 1981, which determined that a 50 percent reduction in acid rain would prevent damage in sensitive freshwater areas. But the 1981 report drew no conclusions on what level of emission control would be needed to reduce acid rain by that amount.

The academy was denied government funding for its follow-up report, but it did the study anyway, using funds from a consortium of foundations.