The Senate Appropriations Committee yesterday caved in to President Carter and adopted a scaled-down substitute for the $10.1 billion public works bill Carter successfully vetoed last week.

The original bill contained funds for 59 water projects, including six that Carter thought he had successfully blocked in a water fight with Congress a year ago.

The new bill would drop those six, plus 11 others he opposes, leaving 42. The cost of these projects would drop accordingly, from $1.8 billion to the $841 million Carter wanted. In addition, the committee agreed to provide full funding for each project in this bill instead of funding some a little at a time to make them seem less expensive, a practice Carter also opposed.

The substitute also cuts out 2,300 newly mandated jobs in the Army Corps of Engineers and the Bureau of Reclamation, as Carter insisted, and restores the Water Resources Council, a planning group he wanted.

The new measure amounts to an almost total victory for Carter in his two-year war with Congress over water policy. The president has advocated an end to expensive water projects that benefit only a small number of people and that make water so inexpensive to some users that it is wasted.

The victory for Carter was in sharp contrast to a year ago, when the president failed to follow through on his veto threats and some projects he opposed were voted into law. He said after that experience he regretted not vetoing last year's bill, and this year he held firm despite strong opposition from congressional leaders.

Sen. L. Bennett Johnston (D-La.) said yesterday the congressional cave-in was a "result of necessity and practicality."

The substitute measure, adopted 13 to 3, was added to a resolution to continue funding for the departments of Defense, Labor, and Health, Education and Welfare. The Senate is expected to take up that resolution today.

Rep. Tom Bevill (D-Ala.), chairman of the House Appropriations public works subcommittee, said the House likely would accept the Senate action without a fightover water projects. In addition to water projects and other public works, the bill contains $6 billion in funding for energy programs and the Department of Energy.

Bevill conceded the outcome was a victory for Carter, but doubted that it would affect inflation much since the amount being argued over was "less than one-half of 1 percent" of the amount in the bill.

Carter had called the bill "inflationary" and wasteful.

But mostly he was attempting to curb Congress' treatment of water as a pork-barrel commodity, funding projects simply because colleagues wanted or needed them and ignoring cost or effect on the environment or the number of people benefited.

Carter also demanded that the legislators fully fund projects from the start, rather than merely making a down payment, a device Carter said led to concealment of true costs and made projects difficult to kill once funded.

One Oklahoma project would have benefited only a few catfish farmers. One result of the project is that water is often cheaper in the West - where it is scarce - than in the East.

However, some representatives and senators remain bitter over the battle. Sen. Walter D. Huddleston (D-Ky.), whose state had a project in Yatesville dropped, said, "If we totally capitulate we may never again write a publics works bill in the Senate." he claimed Congress would have conceded to the president a congressional preorgative.

Democratic House leaders told Carter his veto of the projects could jeopardize a House vote on the energy bill, scheduled for today.