All net revenues, rents, and earnings from the operation or maintenance of any state-owned inland port or harbor, or any part thereof, shall be set aside by the board exclusively for the payment of any bonds issued by the state for such port or harbor, or any part thereof, and shall not be commingled with the funds of any other port or harbor, or any part thereof, but shall be expended by the board exclusively for the payment of such bonds as provided in Section 59-17-51, and, if no such bonds be outstanding, then by the state inland port authority for the improvement, operation, advancement, development, maintenance and advertising of the port to which such funds have accrued.
