The Senate Environment and Public Works Committee, in a surprise move, voted yesterday to recommend a halt in construction of the Tennessee-Tombigbee Waterway, a $2 billion barge canal that environmentalists have been fighting for 10 years.

The 9-to-4 vote signals a new antagonism in the Senate toward pork-barrel water projects, said Sen. Alan Simpson (R-Wyo.), whose motion led to the decision. Liz Kaplan of the Friends of the Earth added it was also "a very important message that the West is flexing its muscles over water development."

But Sen. John C. Stennis (D-Miss.), a major sponsor of the waterway, promised to do everything possible to see that the new Senate mood goes no further. "This is solely a recommendation to the Budget Committee," he noted. "There will be other votes." To stop the project now, he said, would be "an intolerable waste of taxpayers' money."

Although not a member of the committee, Stennis showed up to speak against the vote, complaining he had been given only 15 minutes' notice that it was being taken. Simpson denied that."Stennis is an old friend of the family . . . but this project is the very epitome of waste. It's moving more dirt than [came out of] the Panama Canal," Simpson said.

The committee voted to limit 1982 spending on the waterway to $25 million, enough to finish work in progress on the southern third from Columbus, Miss., to Demopolis, Ala. The project -- first proposed in 1760 by the town fathers of Mobile, Ala., to the King of France -- was finally launched under President Johnson. The Tenn-Tom, as it is popularly known, woiuld run 232 miles from a point on the Tennessee River near the Alabama-Mississippi-Tennessee junction through 10 locks down the Tombigbee River east of Tupelo, Miss., to Columbus and on to Demopolis.

That much would cost $1.9 billion, according to the Army Corps of Engineers, of which roughly $1.2 billion has already been spent. Critics say $1 billion more would be needed to widen and straighten the Tombigbee south to Mobile in order to complete the project's goal of linking the coal fields of Ohio and Kentucky to the Gulf of Mexico. The project backers say that when comnpleted in 1986, it would shorten the trip for coal barges by as much as 800 miles, for a savings of $2.60 per ton of coal.

The Environmental Defense Fund filed the first suit to stop the canal in 1971, and former executive director William Butler, who is now with the Audubon Society, was jubilant over yesterday's vote. "We thought it was totally unnecessary to four-lane the Mississippi River" 100 miles to the west, he said. "The route is completely political, environmentally ruinous is destroying farms, mixing river waters and creating mountains of spoil. And the barge interests are getting the taxpayers to pay for it."

Simpson initially asked that President Reagan's entire $176.9 million request be denied, but Sen. Pete V. Domenici (R-N.M.), who chairs the Senate Budget Committee, noted that the Army Corps of Engineers might take that cut out of other water projects instead of the Tenn-Tom. He offered a substitute to limit Tenn-Tom spending to $25 million in windup funding, which Simpson accepted.

In Gadsden, Ala., Rep. Tom Bevill (D-Ala.), chairman of the House energy and water appropriations subcommittee, predicted the project would be revived in the House. "It's 55 percent complete and 88 percent of the contracts have been let. It would be foolish to stop this project," he said.

Elsewhere yesterday, Interior Secretary James Watt opened his budget cut defense before the Senate Energy and Natural Resources Committee by taking the offensive, calling on environmentalists "to join us in protecting the resource base" instead of attacking him for ending park purchases.

And Sen. Henry Jackson (D-Wash.), signaling the tack Watt's opponents are likely to take, objected to "setting a precedent" by using park purchase money to maintain parks instead.

Watt also defended his assault on the Office of Surface Mining, which lost a third of its funding. "Some of those personalities have a right to feel gutted and should have been sooner than they were," he said. "We trimmed the fat and if that's gutting I'm proud of it."