ALONG WITH EVERYTHING else, President Carter is taking a beating in Congress on the water-policy front. Despite his veto threats, Senate-House conferees have voted funds for six of the public-works projects that Mr. Carter thought had been shelved last year. Meanwhile, both houses have largely rejected the stricker standards and new planning procedures Mr. Carter has proposed. In the most outrageous move of all, the House Public Works Committee is advancing a $1.2-billion-plus grab bag of authorizations for about 120 more river and harbor projects - including dozens that don't meet the panel's own standards for executive-branch review, local cost-sharing and the like.

How can Mr. Carter salvage something, or even avoid a rout? Some officials and environmental lobbyists think he needs to "get tough." As they see it, the administration only encouraged the old-time forces by accepting a compromise in last year's water-projects fight and trimming its proposals last winter to appease the Western governors. What's needed now, according to this view, is some stern vetoes and stiff stands on principles. Mr. Carter apparently agrees; he said recently that he had been "too lenient" and "should have vetoed" last year's money bill - just as he plans to veto the one now coming along.

We see the problem differently. Far from yielding too much to politics, Mr. Carter has not been consistently political enough. Tending to oppose many projects as "pork barrel," he and some of his advisers have been slow to understand the viewpoint and ferocity of the regional and institutional forces they have taken on - or the way public-works hassles can affect all other dealings on Capitol Hill. We think it was prudent to made some accommodations last year, after the first clumsy assault on those projects had caused such an unholy row on the Hill and in the West. The real error was in assuming that the truces would last, that projects once shelved would stay on the shelf, and that entrenched congressional attitudes could be transformed by sending up some better ideas.

By now, Mr. Carter should have a better sence of what he is up against - and what kind of toughness can accomplish most. Some vetoes and stern speeches will probably be in order, starting with the public-works appropriations bill. But to have those vetoes sustained, and to defuse other confrontations, holding the high ground of environmental protection and economic prudence will not be enough. More hard-headed dealing will also be required. We hope this can be done with more finesse than in the past. We also hope the administration will get over the idea that this kind of politicking is somehow shabby, demeaning or inconsistent with its commitment to change. After all, when you're talking about public works, you ought to use the language that every member of Congress understands.