The board of commissioners of any drainage district organized under the laws of the state of Idaho may issue negotiable coupon bonds, to be denominated refunding bonds, for the purpose of refunding any of the bonded indebtedness of the district, whether due or not due, on which has or may hereafter become payable at the option of the district or by consent of the bondholders, or by any lawful means, whether such bonded indebtedness be now existing or may hereafter be created, and there shall not be funds in the treasury of such district available for the payment or redemption of such bonds and the accrued and unpaid interest thereon.