White House staff aides are preparing some "middle ground options" as the April 15 deadline approaches for President Carter to make public a final list of water projects he wants terminated, according to administration sources.

One series of alternatives under study would permit the President to recommend that a portion, but not all, of a currently planned project be completed.

"In some cases we can justify doing a piece of a project," a White House aide said yesterday, "and eliminate a major environmental problem by not doing the whole thing."

Some major projects that are under White House review might be handled in such a manner. Rep. Morris Udall (D-Ariz.), for example, recommended such a course for the $1.8 billion Central Arizona Project during a public hearing last month.

Until now, it had been assumed Carter would recommend to Congress that funding of an entire project be halted or continued, as a result of extensive agency reviews and public hearings held over the past two weeks.

Detailed information on 30 projects that were singled out last month for review was sent to the White House over the weekend from the Corps of Engineers and Bureau of Reclamation.

At the request, of Carter aides, those agency reports did not contain any final recommendations.

"Without a single set of criteria," a top White House aide said yesterday, "we were concerned about the judgments that would then be leaked to the Congress and the press."

The President, according to another aide, "would be boxed into a position of having his decision overrule the agency."

Carter's Office of Management and Budget and Council of Environmental Quality are now reviewing the agency data and coming up with their own recommendations for the President.

Those recommendations will be completed tonight and delivered to Carter either Wednesday or Thursday, according to White House aides.

Because the water projects are a touchy subject among senators and congressmen in affected states, Carter's top political adviser, Hamilton Jordan, and his chief congressional liaison man, Frank Moore, are expected to take part in the final decision-making.

A White House aide said yesterday that Carter may not meet his self-announced deadline of April 15 - "depending a little on the time he spends" reviewing the agency data and his staff recommendations.

Public announcement may be delayed in any event to permit the news to be given first to Congress after members return April 18 from the Easter recess.

Interior Secretary Cecil D. Andrus is expected to ask for a meeting with Carter later this week to present his department's recommendations before a final decision is made. No time for Andrus had been set as of yesterday, and a White House aide said such a session would depend on "questions Carter may want to ask."

Army Secretary Clifford Alexander, who directs the Corps of Engineers, also has no meeting yet scheduled.