In the event that such revenues from the operation of any such revenue-producing project financed by such bonds shall be available for the payment of debt service on such bonds (whether or not such revenues have been pledged for that purpose), and shall be delivered to the county treasurer (or to such other public official who is charged with the duty of collecting the annual ad valorem tax to pay the annual principal and interest on such bonds) for the payment of such principal and interest and for no other purpose, prior to the occasion when the county auditor (or such other public official who is charged with the duty of making the levy for the annual ad valorem tax to pay the annual principal and interest on such bonds) fixes the annual tax levy, the annual ad valorem tax to be levied for the payment of the principal and interest on such bonds may be reduced in each year by the amount of such revenues derived from such project which is actually in the hands of the county treasurer (or such other public official who is charged with collecting such annual ad valorem tax) at the time the tax for the year is required to be levied.