UNDER HEAVY PRESSURE from the Carter administration, both houses of Congress agreed last year to abandon the old federal policy of paying the bills for the nation's inland waterways out of general tax revenue. The Senate did it in a way that would make a difference: The costs of the barge operators who use the waterways would go up sharply. The House acted in a way to keep the cost increases so low that its version appears more symbolic then real. When the Senate considers the matter again today, it should insist upon its version. A symbolic move won't end the waterways' constant drain on the Treasury.

The Senate bill rests on two premises. One is that the charges paid by each barge company should be related to the cost of the facilities it uses. The other is that the ever-present pressure to expand and improve the waterways will be reduced if those who want the improvements know that part of the costs will be passed on directly to them. Thus, the bill sponsored by Sen. Pete Domenici (R-N.M.) would impose fees or tolls for the use of such things as locks.

The House bill rejects both premises and simply imposes a tax on the fuel used by barges. This has the advantage of spreading the cost across the barge industry. But it would have no effect at all in discouraging pressure for new facilities. In addition, Sen. Domenici's bill would generate enough revenue in the long run to cover most of the government's expenses, while the House bill would bring in less than 10 percent of what the government spends.

Sen. Domenici's version has the weight of logic behind it. It relates the charges each company would pay to the benefits it gains. And it removes part of the incentivefor logrolling in Congress, which has kept the Corps of Engineers busy for decades building locks, dredging river bottoms and straightening channels.

It is probably true, as the barge companies contend, that his proposal would increase substantially the freight costs of some shippers and drive some freight from the waterways to the railroads. But that is fair enough. The federal subsidy down through the years has allowed the barge operators to skim off traffic that would otherwise have gone to the railroads, and this, in turn, has helped produce the present situation in which many railroads need federal help to survive. That arrangement must change if there is to be a rational federal transportation policy. Sen. Domenici's approach provides a change, instead of a gesture.