The board of directors of any irrigation 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, or 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; but the amount of such refunding bonds to be issued under the provisions of this chapter shall first be determined by such directors, and a certificate of such determination shall be made and entered in and upon the records of said district prior to the issuance of said refunding bonds.