To amend the act of June 3, 1960 (74 Stat. 156), to provide additional authority for the Secretary of the Interior to construct the San Luis Unit, Central Valley Project, California, and for other purposes.

Increases from 500,000 to 600,000 the number of acres which the San Luis unit of the Central Valley irrigation project, California, is authorized to service. Enumerates the principal engineering features comprising the Unit. Defines the "Federal San Luis Service Area" for purposes of this Act.

Limits the capacity and scope of the drainage system for the San Luis unit (San Luis drain), to a capacity of not more than 300 cubic feet per second between the Kesterson Reservoir and Kettleman City, California. Sets forth the conditions which must be met by the Secretary of the Interior before further construction will be permitted.

Conditions all future appropriations for construction within the San Luis unit upon the execution with all water districts within the unit of long term contracts which contain rates adequate to recover annual costs of operation, maintenance, and replacement, and to recover within 40 years an average share of the Central Valley Project capital costs allocated to irrigation and full repayment of distribution and drainage system costs by the districts which benefit from those systems.

Limits to 1,100,000 acre-feet annually long term contractual commitments for firm surface water deliveries to water districts or municipalities in the San Luis unit. Provides for the reduction of such limit during dry years, and for the supply of additional water under specified conditions.

Requires Congressional approval of any water service or repayment contract and the opportunity for a public hearing on any such contract in the affected area.

Prohibits the delivery, exchange, or sale of Federal project water for use on excess lands within the San Luis unit service area which are held by one owner in excess of the acreage limitation of reclamation law, unless such lands are under recordable contract. Prohibits the use of such water outside the service area except by written approval of the Secretary of the Interior.

Directs the Secretary, acting with water users in the San Luis unit, and the State, to develop a program for the most efficient use of water within the unit and adjacent lands.

Increases the authorization of appropriations for distributions and drains for the unit.