Idaho Code § 42-2812
The board of county commissioners of any county in which any irrigation or drainage project is established under this chapter are authorized to provide by resolution for a sinking fund for the payment of the bonds issued under the provisions of this chapter and for such purpose and in order to provide a fund to meet all payments of the principal and interest on such bonds as the same come due and to cover deficiencies or delays in collections shall provide an assessment each year, ten per cent (10%) in excess of the amount of the principal and interest coming due the following year on the bonds issued by such county under this chapter until such time as a reserve fund shall have been accumulated in the county treasury from such excess assessments to an amount of at least ten per cent (10%) of the bonds issued by such county for such irrigation or drainage project.
Idaho Code § 42-2812