All moneys received by the United States in connection with any irrigation projects, including the incidental power features thereof, constructed by the Secretary of the Interior through the Bureau of Reclamation, and financed in whole or in part with moneys heretofore or hereafter appropriated or allocated therefor by the Federal Government, shall be covered into the reclamation fund, except in cases where provision has been made by law or contract for the use of such revenues for the benefit of users of water from such project: Provided, That after the net revenues derived from the sale of power developed in connection with any of said projects shall have repaid those construction costs of such project allocated to power to be repaid by power revenues therefrom and shall no longer be required to meet the contractual obligations of the United States, then said net revenues derived from the sale of power developed in connection with such project shall, after the close of each fiscal year, be transferred to and covered into the General Treasury as "miscellaneous receipts": Provided further, That nothing in this section shall be construed to amend the Boulder Canyon Project Act (45 Stat. 1057), as amended [43 U.S.C. 617 et seq.], or to apply to irrigation projects of the Office of Indian Affairs.