San Francisco — Ask supermarket shoppers if they know what the Reclamation Act of 1902 is and you most likely will get blank stares. As price-conscious as they are, most people aren't aware that the act, which regulates the cost of irrigation water to farms in 17 Western states, has a direct bearing on the price of a can of tomatoes or a cotton blouse.
A conference committee of the US House and Senate is working to reconcile two versions of a measure which, in effect, attempts to bring 80-year-old rules on access to and cost of federal water into harmony with today's agricultural practices in those states.
The Reclamation Act placed a 160-acre limit (320 acres for a married couple) on the size of a farm using inexpensive water from a federal reservoir. Larger farms are supposed to pay a fee more in line with the actual value of the water.
For years the acreage limitation, originally aimed at encouraging families to homestead in the West, was more-or-less ignored. It did not take long to learn, explains Harry Krade of the California Department of Food and Agriculture, that farms of at least 640 acres were much more adaptable to growing irrigated crops of tomatoes, lettuce, grain, and cotton in arid regions such as this state's San Joaquin Valley.
But, beginning in the mid-1970s, the federal courts began forcing compliance with the original limitations. This did not put the big farm operations out of business, but it did raise their costs. Thus, a drive to change the law began with the support of state agriculture departments and most Western members of Congress. Sens. Alan Cranston (D) of California and Malcom Wallop (R) of Wyoming are among the advocates of liberalized acreage limits; Sens. Howard Metzenbaum (D) of Ohio and William Proxmire (D) of Wisconsin have led the opposition in that chamber. Among other opponents are the Sierra Club and the AFL-CIO.
After much delay and some bitter debate, two versions of the amended act emerged: the House bill, passed in May, makes the federal water subsidy available to farms of up to 960 acres and eliminates a largely ignored requirement that the owner must live on the farm. Water for an additional 400 acres would be available at increased cost.
The Senate bill, passed July 16, differs chiefly in the acreage limit for cheap water, which it places at 1,280 acres. Before it was amended, the Senate proposal put the acreage limit at 2,080 acres.
President Reagan supported both bills and is expected to sign the compromise legislation when it is sent to the White House.
What of the effect on the consumer - and the ''family farm''?
''I think this law (the proposed revision) will tend to hold consumer prices down,'' says Baker Conrad, director of information for the Council of California Growers, an organization dominated by the large operators. Mr. Conrad notes that certain crops, such as strawberries and cherry tomatoes, are best produced on small land units. If the 1902 limits are enforced, he says, there might be increased production of such crops, with lower prices in the market at first. ''But profits would be too low. Eventually farms would go out of business and prices would rise.''
As for the major California and Western crops affected by the proposed revisions - cotton, tomatoes, melons, lettuce, grapes, alfalfa, and sugar beets - Conrad says: ''I think this law will tend to hold consumer prices down.'' Failure to revise the water law, he argues, will result in ''a falloff in production and a major change in pattern of farming in the West.''
The Sierra Club expresses the chief objections to the change: ''It continues massive subsidies to large corporations and encourages unwise farm practices. . . . The 1902 Reclamation Law was enacted to protect the small farmer,'' but the revision proposed ''ignores this in favor of a few wealthy agribusinesses.''
But Harry Krade says the ''small farm'' concept is misapplied in much of the arid West. He explains that part of California's agricultural ''heartland,'' the San Joaquin Valley, supports smaller units where mostly fruits and nuts are grown. But in the larger, dryer part of the valley, field crops are grown - and farms must be larger to pay off.
Mr. Krade adds that although the average farm size in California is about 500 acres, this figure is misleading. Included are ''a large number of part-time and gentleman-farmer operations of 5 to 20 acres. In the San Joaquin the average is more like 640 acres.''
Even where landholdings in the valley meet the 1902 acreage limit, the fact is that one operator is doing the work over extensive acreage for several owners , Krade points out.
''Failure to change the Reclamation Act,'' he contends, ''would substanially change the structure (of agriculture) in much of West. It would even result in some abandonment of farms.''
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