The Senate gave overwhelming approval yesterday to a public works appropriations bill including money for disputed water projects that President Carter is now expected to veto.

The Senate vote was 86 to 9 on a House-Senate conference report that will now go to the White House. Senior White House aides have been meeting daily since Sept. 8 to plan strategy for a veto of the bill, which would be an extremely unusual event.

Ordinarily, "pork barrel" public works legislation is a sacrosanct congressional prerogative. But Carter has publicly rued his failure to veto last year's public works appropriations, and the comments of White House officials make clear their belief that he will veto this bill now.

Carter himself came close to a declaration of intention to veto the $10.2 billion measure at a meeting with about 30 House members yesterday who gathered to hear his reasons for disapproving the legislation.

Warned by some present that a veto of the bill might cost him House votes on the natural gas legislation that he regards as crucial, Carter indicated this would not stop him.

The Senate passed that natural gas legislation yesterday, and a final vote in the House is scheduled for Oct. 12. A veto of the public works bill and a vote to override the veto seem likely to occur before then, though both Carter and the congressional leadership have the authority to postpone these actions if they want to.

Both House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) and Majority Leader Jim Wright (D-Tex.) warned yesterday that Carter would be taking a grave risk with the gas legislation if he insists on vetoing the public works bill.

Carter opposes the bill, he says, because it virtually obliterates his efforts to establish a rational new policy on federally funded water projects.

He is furious that Congress has revived six of the water projects he mistakenly thought had been killed forever last year in the compromise resolution of the dispute he created with his "hit list" of undersirable water schemes.

The president also argues that Congress' new approach is wasteful and misleading, since it involves appropriating modest sums this year to begin 53 water projects that will eventually require additional appropriations of hundreds of millions of dollars.

The administration had proposed a water projects budget that would have fully funded 26 new projects. Though most other government construction projects are fully funded at the time they are initiated, public works projects have traditionally received yearly dollops of funds to pay only or the work done on them during a single fiscal year.

By ignoring the administration's proposal for full initial funding - a proposal the White House and Senate Public Works committes have produced legislation that they claim is actually $879 million less than Carter originally requested.

The White House - which has already produced a pile of documents two inches thick arguing against the bill - replies that, in fact the conference report would actually cost $1.8 billion more than Carter requested when all the projects it funds are fully built.

Administration officials note that big projects begun in this bill with small appropriations could eat up big portions of future Carter budgets, and the president would be unable to control this spending.

The White House also criticizes the measure for mandating the hiring of 2,300 new federal employes, mostly in the Corps of Engineers, and for abolishing the interagency Water Resources Council, a body Carter intended to formulate a comprehensive new water policy.

The prospect for sustaining a veto in Congress were unclear yesterday. The House and Senate both passed the legislation with huge majorities, more than enough to override a veta if they were repeated but this seems unlikely.

Majority Leader Wright predicted that a Carter veto would be narrowly sustained in the House, which would cause the president "very, very serious" political problems with members who would resent the veto. They might take out their resentment on the gas bill, Wright implied.