Three Californians, two of them Cabinet members and all longtime intimates of President Reagan, have teamed up to scuttle a proposal by Office of Management and Budget Director David A. Stockman to do away with the pro-western Bureau of Reclamation by creating a single federal water agency.

The OMB proposed on Friday to merge the bureau, overseer of most major federal irrigation and other water projects in the 17 western states, with the U.S. Army Corps of Engineers, which handles flood control and navigation nationwide. The combined agency was to be under the Department of Defense.

Stockman has struggled throughout his tenure to force beneficiaries of federal water projects to pay more of their cost.

He has been thwarted several times by western interests, including Sen. Paul Laxalt (R-Nev.), a close friend of Reagan.

The merger proposal ran into instant objections from Interior Secretary William P. Clark, whose department has run the bureau for 82 years, helping to underwrite development of the West with cheap irrigation water.

Clark called for reinforcements in the persons of White House counselor Edwin Meese III and Defense Secretary Caspar W. Weinberger, who oversees the corps. The three were key members of Reagan's team when he was governor of California, and once collaborated to block a controversial high dam proposal sponsored by the corps.

By yesterday, the proposal was "deader than the proverbial doornail," in the words of one White House official, although no one would describe how the issue was brought to Reagan to resolve.

"The Bureau of Reclamation will remain on this side of the Potomac," Clark said through a spokesman yesterday, a reference to the fact that the Pentagon is across the river from his department.

"We don't want the bureau," said Weinberger, who added that he was not told of the plan before it was proposed. "We think the present arrangement is perfectly satisfactory."

An OMB official said the merger would have "eliminated duplication" between the agencies, and called the opposition "purely political."

Both the corps and the bureau build dams and operate hydroelectric power facilities. But the bureau is concerned mainly with irrigation and water supply, while the corps was organized for navigation and flood control.

"The corps and the bureau do essentially the same work and fill the same need," the OMB official said. "They have a duplicate set of engineers, a duplicate set of surveyors, a duplicate set of almost everything."

This view is not shared by most western state officials or development interests. They regard the bureau as an advocate for their region within the federal bureaucracy. It was created in 1902 to help "reclaim" arid, western settlements with irrigation and to supply drinking water. Many westerners call the corps, by contrast, an "eastern" agency.

The merger "would be very unsettling in the West because the bureau has such a history there," Clark said. "Its work is closely integrated with state and local governments and with federal agencies such as the National Park Service. Doing away with it would be illogical and infeasible from a fiscal and managerial standpoint."