Among the hardy legislative perennials that blossom in Washington every spring is a short-lived species called a "waterway user charge bill" that puts forth a simple idea: those who ship freight on the nation's canals and rivers should help the government pay for building and maintaining those waterways.

Traditionally, the legislation is launched with a glowing press release pointing out that it would save the government hundreds of millions of dollars annually and eliminate a fundamental inequity of national transportation policy.

And traditionally, the nation's barge operators, who have never paid a penny to use the multi-billion-dollar network of channels, locks and dams built for them by the Army Engineers, manage to sink the legislation before it navigates even the first step toward passage.

That traditional pattern seemed to be extending itself one afternoon last month when Sen. Pete Domenici, an amiable Republican from New Mexico, strolled to the front of the Senate chamber and plopped a user charge bill on the long marble desk.

But this year, the pattern of quick death for such legislation may be broken. Because of new attitudes in the executive branch, a series of new studies of transportation policy and a surprisingly favorable vote last year in a Senate committee, Domenici's bill - designated S.790 - has a fair chance to become law.

Accordingly, the nation's barge operators and their customers are gearing up for an all-out effort to stop S.790.

They have retained a battery of lawyers, including two ex-senators and Richard Nixon's chief White House lobbyist, to argue for the status quo.

Bargemen have become regular visitors in Senate offices, and they have invited senators to return the favor. Last month, for example, a barge association paid a $1,000 honorarium for a 30-minute fidlle recital, by Majority Leader Robert C. Byrd (D-W. Va.).

Meanwhile, an ad hoc alliance of transportation executives, unions, environmentalists and economists is preparing to wage equally strenuous battle on behalf of the Domenici bill.

These who favor a water-way user charge cite arguments of equity, economy and environment.

It is inequitable, they say, for the government to provide free facilities to one form of transit while other modest must pay. "Highway and airport users pay taxes into a trust fund," Domenici says. "Railroads and pipelines must go into the private capital markets for their right-of-way funds. But the barge industry gets a free ride."

Proponents add that a government facing a $60 billion budget deficit can no longer afford to foot the $240 million annual bill for operating and maintaining the nation's inland waterways - not to mention hundreds of millions more ofr new construction.

Environmentalists, who see the Army's corps of dredgers and dam builders as a scourge upon the earth, think the political pressure for new locks, dams, and waterways would decrease if the bargemen had to help pay for the projects they push through Congress.

On the other side, barge operators argue that waterway tolls would reverse a tradition as old as the Republic.

The bargemen recite from memory a section of the Northwest Ordinance of 1787 guaranteeing that inland waterways "shall be common highways and forever free . . . without any tax, impost, or duty therefor."

To complement that ancient rationale, the barge operators offer a modern one: energy conservation.

They argue - and government figures bear them out - that a barge is one of the most energy-efficient ways to move bulk freights. To institute tolls now would discourage barge use at a time when the nation most needs it, the bargement say.

Most government agencies and independent observers who have weighed the competing arguments come down on the side of some user charge for the waterways. Every administration since Franklin Roosevelt's has backed a user charge, and a host of recent studies has supported these recommendations.

In his Senate confirmation hearings, the new Transportation Secretary, Brock Adams, called a user charge both "justified" and "desirable."

In Congress, however, these policy considerations have taken a back seat to politics. Coincidences of geography and political longevity have given the barge operators friends in high congressional places.

Barge traffic moving down the Mississippi runs through the back yard of Judiciary Committee Chairman James Eastland (D-Miss.) and Armed Services Committee Chairman John C. Stennis (D-Miss.) on its way to the port of New Orleans, home base of Finance Committee Chairman Russell Long (D-La.)

Feeding into the Mississippi is the $1.2 billion McClellan-Kerr Arkansas River barge channel, which was completed in 1971 and named in part for Appropriations Committee Chairman John McClellan (D-Ark.), who was one of its chief congressional patrons.

The only major waterway west of the Arkansas, the Columbia-Snake River system, snakes through the constituency of Commerce Committee Chairman Warren Magnuson (D-Wash.) and Energy Committee Chairman Henry Jackson (D-Wash.).

With friends like that supporting their fight against tolls, the waterway interests would seem to have little to fear from an adversary like Domenici, whose most important position is the ranking minority seat on the Senate Subcommittee on the Upper Atmosphere.

But Domenici, for all his casual, country-boy manner, had carefully taken the measure of his opposition before introducing his bill, and devised a strategy to confound the forces arrayed against him.

To win passage of a bill that had powerful enemies, he would link it to a bill that had powerful friends. With little trouble he found the perfect vehicle: the user charge plan would be submitted as an addendum to a bill calling for revamping Lock and Dam 26.

Lock and Dam 26 (it is the 26th facility a barge passes on the downriver haul from Minneapolis) stands at Alton, Ill., near the confluence of the Mississippi, Illinois, and Missouri rivers, and is thus the pivot point of the nation's major water highway.

Aging, outmoded, too small for the modern "jumbo" barge, the lock has been targeted by bargemen as the chief obstacle to expansion of Midwest water shipping. The industry is seeking $400 million to expand and rebuild the facility.

Logically, the links between Lock 26 and the user charge plan are just close enough to let Domenici merge them in a single bill. Politically, the linkage is precisely right: the very opponents of user charges are the chief advocates of rebuilding the lock.

Bills that are joined can be unjoined, of course, on the Senate floor. But the linkage with Lock 26 would help Domenici get his bill into and out of a committee; late last year, he pushed a joint user charge-Lock 26 bill through the Public Works Committee (it was dumped in parliamentary maneuvering on the floor). And the connection with the $400 million Lock 26 project would provide a continuing reminder of how much money the government spends on toll-free waterways.

There is a certain justice in Domenici's linking those two issues, because it was Lock 26 that first brought the waterways to the New Mexican's attention.

As a junior member of the Water Resources Subcommittee of the Public Works Committee, Domenici has sat through countless hearings where rivermen presented ambitious and expensive plans for a new lock.

"There was an awful lot of money at stake," Domenici says. "You know that $400 million estimate is just a beginning. And I kep thinking, why should people in New Mexico pay that much for something that was mainly going to benefit the Mississippi basin?"

At yet another Lock 26 hearing last fall, Domenici lost patience. He stormed out of the room, pausing at the door just long enough to grumble.

"This is screwy - get me a user charge bill."

The targets of that grumble, Hal Brayman and Lee Rawls, were two young Domenici staff aides who are accustomed to cryptic directions from the boss.

"The senator is an idea man," Rawls says. "He's always hitting on some brainstorm he wants to legislate on. He's always telling us to write him a bill."

Among the ideas Domenici has thrown at Rawls and Brayman was an automobile excise tax pegged to the amount of air pollution each model caused. (The staff quickly discarded that one, only to see another senator introduce it, to editorial acclaim, a few months later.) Another would have eliminated federal regulation of trucking rates; that, too, died under the staff's criticism.

But waterway tolls hit more fertile ground. Brayman, a seven-year veteran of the Public Works Committee staff, had long thought that bargemen were getting an undeserved free ride from the government. He had convinced Rawls, and the two jumped at the chance to write a bill for Domenici.

Explaining the bill in conversation recently, Brayman said, "We're phasing in, over 10 years, charges that will make the barges pay half the government's cost of building and servicing the waterways."

But such direct language would never do for an actual piece of legislation. There are no "barges" in S.790; the bill applies to "shallow draft cargo vessels." The phrase "half the government's cost" becomes, in legislative argot, "50 per centum of the Federal navigation-related expenditures." The plan Brayman described in 23 words consumes five pages of legalese in the bill itself.

With their user charge translated into the necessary verbiage, the two stapled last year's Lock 26 authorization bill to the front of it.

For balance, they stapled at the end six more pages from a bill creating a "Mississippi River System Council." Such a council is a dream of Sen. John Culver (D-Iowa), whose support Domenici would need to pass the user charge provision.

Finally, Rawls and Brayman wrote an explanatory "speech" (which they knew would never be spoken) and handed the whole passage to Domenici for delivery to the marble desk in the Senate chamber.

As he carried his brainchild to the Senate floor, Domenici was already thinking about the rough road ahead. Unless he could make some arrangements, S.790 would die beneath the thumb of a hostile committee chairman.

(Next: Maneuvering past the chairmen.)