The Secretary of the Interior is authorized to contract for the delivery of water to public organizations or agencies for use within the boundaries of such organizations or agencies for waterfowl purposes in the Grasslands area of the San Joaquin Valley. If and when available, such water shall be delivered from the Central Valley project to the contracting entity, and the cost of furnishing the water shall not be reimbursable or returnable under the Federal reclamation laws: Provided, That, in order for the delivery of such water to continue on a nonreimbursable or nonreturnable basis—