Idaho Code § 43-608
The board of directors of the district shall annually at the time provided by law for making tax levies for original bond issues, or as soon thereafter as practicable, levy a separate tax for the purpose of discharging the interest upon and the principal of any refunding bonds issued, registered and outstanding pursuant to the provisions of this chapter. Such taxes shall be levied and collected in the manner provided by law for the levy and collection of taxes for the payment of interest and principal of original bond issues, and such refunding bonds and the interest thereon shall be paid from the revenue derived from the annual assessment on the land in the district and all the land in the district shall be and remain liable to be assessed for such payment.
Idaho Code § 43-608