Colo. Rev. Stat. § 37-43-144
The board of directors of any irrigation district, under the conditions provided in sections 37-43-144 to 37-43-151, may issue negotiable coupon bonds, denominated as refunding bonds for the purpose of taking up, paying off, and refunding any outstanding indebtedness of the district, whether due or not and whether such indebtedness is now existing or may be created, when there are not funds in the treasury in such district available for the payment of such indebtedness. Such refunding bonds sought to be issued shall not exceed the amount lawfully owing and unpaid upon such indebtedness so to be taken up, paid, and refunded. Such refunding bonds shall not bear interest greater in rate or amount per annum than that borne by the indebtedness to be taken up, paid, and refunded. The authority vested in the board of directors by any election held pursuant to sections 37-43-144 to 37-43-151 shall be and remain effective until the indebtedness so authorized to be refunded has been paid, redeemed, or refunded. Such refunding bonds may be issued and used to pay off all or part of any indebtedness then outstanding.
C.R.S. § 37-43-144