Whenever any amount of money shall have been advanced by the United States for the construction of irrigation works, contemplated under the provisions of this title, by the authority of act of congress hereinbefore referred to, the taxing powers of the district, as provided in this title, shall be used to repay into the treasury of the United States the amount of money so advanced in the manner contemplated in this title, and as may be provided in such contract between the directors of said district and the United States; and such levies and assessments shall be made each year under the authority of the district as will return to the treasury of the United States the amount or proportion of such money advanced as may have been agreed to in such contract.