Whenever any drainage district has issued bonds and the same are outstanding and unpaid, and the same have been outstanding and unpaid for more than three (3) years, the district may, in the manner hereafter provided, issue and sell bonds for the purpose of paying and redeeming such outstanding bonds, and may call and pay said bonds, or at its option, may authorize the issue of sufficient bonds to pay and redeem the whole of such outstanding bonds, but may issue and sell the same in such amounts from year to year, as will pay and redeem the outstanding bonds falling due each year, and may continue to issue and sell such refunding bonds until the whole of the outstanding bond issue, which has been refunded, is paid and redeemed.