In a mood of something-for-everyone, including a monument to dam builders, a House Public Works sub-committee yesterday agreed to buy about $3.5 billion in new water to buy about $3.5 billion in new water projects.

The huge election-year bill contains scores of new projects and seems certain to put Congress on another collision course with President Carter.

Congressional and environmental observers consider the bill a flat rejection of Carter's recent efforts to add coherence to national water development policy.

This time around, the water resources subcommittee, chaired by Rep. Ray Roberts (D-Tex.), produced several new ripples that could intensify the grapping with the White House.

In a number of cases, for example, the subcommittee - acting at the behest of members facing reelection - relieved local communities of their obligation to share in the cost of federal dredging to keep waterways open.

For senior Republican William Harsha of Ohio, the subcommittee agreed to provide full federal for water distribution systems at the Caesar Creek and East Fork reservoirs in his state.

Up to now, the federal government has paid only for the reservoirs - not the distribution systems or the treatment plants. The two Ohio projects will cost and estimated $35.5 million.

President Carter's water policy proposals, released in June, emphasize state-federal cost-sharing on a variety of water projects - a concept that was essentially ignored by the subcommittee.

Still another departure - already approved by the Senate in a companion, but less extensive, bill - would establish more precedent with a dam, or whatever is necessary, to stop flooding along the West Virginia-Kentucky border.

The subcommittee authorized the Army Corps of Engineers to do what it feels it must, without any cost benefit justifications, to bring flood control to the Levis and Tug forks of the Big Sandy River.

It also approved flood-control measures in the upper Cumberland River basin in Kentucky, Virginia and West Virginia on the same basis - build now, ask questions later.

The engineers have long maintained that they could not justify such projects because costs would far outrun benefits.

The West Virginia and Kentucky delegations in Congress, led by Senate Majority Leader Robert C. Byrd and Rep. Carl D. Perkins, have pushed the fight for federal help since the area was devastated by floods in April 1977.

And the subcommittee, in case it runs into trouble later, went out of its way to include language saying that on those projects it - and not the corps - had determined that benefits will exceed costs.

Among a number of newly authorized major projects on the subcommittee's list was a $1.5 billion hydroelectric dam on the Susitna River in Alaska and a navigation and bank-protection scheme for California' Sacramento River.

Roberts said the bill could be taken up by the full Public Works Committee as early as tomorrow. Further additions or changes could occur.

Pete Carlson, a waterways lobbyist with The environmental Policy Center, characterized yesterday's subcommittee action as "trick or treat - Haloween in July."

He said, "the proponents of these things presented their tricks when they testified at the hearing. Now they get from $3 billion to $4 billion in treats."

The Army Engineers, who build an de operate most of the projects the subcommittee authorizes, got special recognition from the Roberts panel.

The bill authorizes erection on federal land in the District of Columbia of A monument to the work of the corps. The money would be raised privately by a Corps of Engineers memorial association.

In that election year spirit of a little bit for as many congressional districts as possible, there was even a goody for one of the sternest critics of the water resources "pork barrel" - Rep. Richard L. Ottinger (D.-N.Y.)

Speaking for ottinger, Rep. Jerome Ambro (D.-N.y.) appealed to the sub-committee to pick up the entire cost of dredging and spoil disposal at Mamaroneck Harbor in New York - at least $500,000 this year.