With a minimum of debate, a Senate Appropriations subcommittee yesterday approved a $10.2 billion water resources-nuclear energy spending bill that has raised presidential veto threats.

The public works appropirations subcommittee's bill, which still must win full committee and Senate passage, allocates about $135 million less than a House-passed version.

The measure contains funds for seven federal water-resource projects opposed by President Carter. The House bill contains money for eight.

Sen. Bennett Johnson (D-La.), subcommittee chairman, conceded that the bill could face trouble but he said he had no recent word from the White House.

He said "The word 'veto' was not mentioned" in a meeting three weeks ago with presidential staff aides, but he indicated that the Senate approach may leave little room for compromise.

"The threat of a veto may be implicit," Johnson said. "I've heard no followup since that meeting. I don't know if it means a confrontation is coming or not."

Among the items of possible confrontation is funding for the Clinch River breeder reactor, a project the administration opposes. The subcommittee bill provides $172 million - $15 million more than the House. A final Senate position on the issue awaits disposition of a separate Department of Energy authorization measure.

Johnson's subcommittee adroitly stepped around an opportunity to plunge into another controversy, however.

The panel sent to the full committee, without comment, a proposal to exempt the Bureau of Reclaimation from developing a comprehensive environmental impact statement covering a series of projected dams in the Colorado River basin.

The proposal was drawn up this week in a meeting of western senators and representatives as a response to a suit filed last month by the Environmental Defence Fund.

The litigation contend - and the BOR's parent Department of Interior has conceded - the National Environmental Protection Act requires a basin-wide impact study, rather than the usual project-by-project study.

Led by Rep. John. J. Rhodes (R-Ariz) and Sen. Dennis Deconcini (D-Ariz), the western bloc drew up the amendment and submitted it to Johnston for inclusion in the appropriations bill.

"It's just too controversial," Johnston said, after the subcommittee decided to bypass the proposal.

Separately, Rhodes cited fears that if the private fund's suit is successful a basin-wide impact study might find at least nine future and costly BOR projects could not be justified.

George W.Pring, an EDF lawyer from Denver, said the suit is not intended to stop projects under construction, but to force the BOR to develop less expensive ways of developing water resources in the West.

"We're are trying to say that the era of dam-oriented projects is over," Pring said."If BOR has to develop a basin wide impact statement, it would find alternatives to the dams that are more economic, more environmentally and socially acceptable".

The western amendment, critized by several senators yesterday as an unacceptable end-run around the environmental law, was drawn up by two dozens legislators from Arizona, Colorado, Utah and Nevada