The Senate yesterday rewrote the federal reclamation law in such a way as to leave most of the huge agribusiness empires in the West intact.

The Senate's revision of the 1902 Reclamation Act fell far short of Carter administration proposals and now faces tenuous going in the House.

Prompted by a phalanx of lobbyists, representing larger irrigators, the revision will exempt at least 2.3 million acres of the world's lushest crop land from acreage limitations.

Some of the bigger winners would not be the "family farmer," whose name was invoked repeatedly during two days of debate, but major corporations with access to water provided through federal tax subsidy.

In California's Imperial Valley, for example, firms such as United Brands Co. and Castle and Cooke Inc. -- two giants of the food processing industry -- would be exempt from acreage limitations set by the bill for the rest of the country.

In the Kings River and Kern River irrigation districts in California's Central Valley, familiar names such as the J. G. Boswell Co. (109,000 acres), Tenneco (64,000), Cheron USA (13,000) and Superior Oil Co. (22,000) also would be exempt.

And in both areas of the state, other large individual farms, whose holdings are thousands of acres above the bill's 1,280-acre limit, would be free of restrictions.

Their champion was Sen. Alan Cranston (D-Calif.), who beat back a series of efforts by Sen. Gaylord Netson (D-Wis.) to limit strictly the amount of land on which the big farm operators could receive federal water.

On the 47-to-23 vote for final passage, both Cranston and Nelson voted against the bill.

During the emotional debate, one senator after another hailed the contributions of the "family farmer" on irrigated land, but the bill that finally emerged may affect him very little.

In the 17 western states where Bureau of Reclamation dams provide low-cost irrigation water for 11 million acres of land, about 96 percent of the farmers are in compliance with the 160-acre limitation set by the 1902 law to promote small farms.

But because the 160-acre limit was only irregularly enforced, farms of immense size were created and the water subsidies have gone to landholders that include railroads, oil companies, canning companies and multinational corporations.

The reclamation program through 1976 had provided some $5 billion in tax subsidies -- water cheaper than its delivery cost -- to irrigators.

Pressure by small-farmer groups to enforce the 1902 law by requiring big operators to dispose of excess holdings led to the Senate rewrite of the act. Under current law more than 1 million acres qualify as "excess." The rewrite would pare the excess figure to about 300,000.

The amount of land involved, the scrambling for the federal water subsidies and the power they imply sent Senate debaters into rhetorical acrobatics.

Sen. James A. McClure (R-Idaho) likened some of the small farmer groups to Marxists. Sen. David L. Boren (D-Okla.) invoked the sancity of private property. Sen. Barry Goldwater (R-Ariz.) said he was "sick and tired" about all the palaver about subsidies. Floor manager Frank Church (D-Idaho) said the program has been "an investment in America" that needed only some fine-tuning to fit the times.

What they really were talking about as they defended the status quo in reclamation, Nelson insisted, was "reform for the rich" and "a bailout for large landowners" and a corporate "ripoff" of taxpayers.

Nelson's main efforts to alter the bill involved California projects -- Imperial Valley and a group of districts in the Central Valley whose water comes through Army Corps of Engineers storage dams.

The bill exempted the Imperial growers from the acreage limitations, on the grounds that they were exempted from the law in the 1930s by the Department of the Interior, notwithstanding later federal court rulings against them.

Nelson failed to get the 550,000 federally irrigated acres in Imperial included in the bill. Inestead, the Senate adopted a Cranston proposal to exempt current owners but to require future owners to pay the full cost of their water.

Cranston also won his fight to keep Kings and Kern River irrigators exempt from the acreage limitations of the bill. Nelson wanted the bill to apply, even though their water is from the corps and not the Bureau of Reclamation.

Under Cranston's approach, Interior would study the cost of the subsidy and then the operators would have the option of paying or withdrawing from from the irrigation districts, leaving them free of the limitations.

But another major district, Westlands, near Fesno, which mounted a massive lobbying effort to weaken the legislation, did not fare as well.

The bill, with its 1,280-acre limitation, its ban on the leasing of additional acres, and its prohibition of large corporate participation in the water subsidy program, would require the sale of thousands of acres of excess lands in the district.

With its 600,000 acres, Westlands is the largest irrigation district in the country. Its bigger landowners include the Southern Pacific Railroad (106,680 acres) and Standard Oil of California (11,593).

A series of efforts by Cranston, Robert Morgan (D-N.C.) and Bob Dole (R-Kan.) would have provided them relief from the limitations through complex financing arrangements, but they were defeated.

Nelson failed in another move to cut the acreage limitation to 640 acres; George McGovern (D-S.D.) failed in an effort to set a 960-acre limit, a level supported by the White House.

Maryland Sen. Paul S. Sarbanes (D) supported McGovern, but Charles McC. Mathias (R-Md.) and Virginians John W. Warner (R) and Harry F. Byrd Jr. (I) opposed him. Similar splits occurred on the 640 acre vote and the Imperial Valley exemption, with only Sarbanes opposing.