Idaho Code § 43-305
Any irrigation district heretofore organized or hereafter to be organized, may, whenever it appears necessary, proper or beneficial to drain any of the lands within said district, whether for the benefit of the land actually requiring drainage or for the protection of other lands within said district, whether the irrigation works have been actually acquired or constructed or not, cause drainage canals and works to be constructed and to this end such district shall in all respects have the same power and authority as is now conferred or may hereafter be conferred respecting irrigation, and all the powers conferred upon irrigation districts under the laws of this state with respect to irrigation shall be construed to include drainage.
Any irrigation district now, or which may hereafter be organized under the laws of the state of Idaho, shall have the authority to construct drainage works for the purpose of draining any land or lands within such irrigation district, and such authority shall be exercised by the board of directors in its discretion. The cost of any such drainage works may be paid for out of the maintenance, operation charges, tolls, or assessments, or out of either or all of such funds which are not otherwise necessary for the purposes for which such funds were created; that not to exceed twenty per cent (20%) of the total amount of such maintenance, operation charges, tolls and assessments for any year shall be expended for drainage.
In all cases where the construction of drainage works requires the issuance of bonds or such works are constructed by the United States under a contract by which the payments therefor are deferred, the board of directors of such irrigation district shall apportion the cost of such drainage works to each tract of land in said district according to benefits. In determining the amount to be apportioned to each tract of benefits under this section, the board of directors may consider benefits to each tract drained; the damage done to the low land from seepage and saturation from irrigation water from high land, and the necessity for carrying off waste water, and such high land may be considered as being benefited to the extent and in the amount that such lands are responsible for damage to low lands from seepage and saturation by irrigation water; the board may also consider any advantage to the lands of the district and each tract thereof, growing out of the construction of such drainage works. In lieu of issuing bonds or contracting with the United States for the construction of drainage works, the board of directors may consider such drainage works as a part of the irrigation system and may make levies to pay for the same upon the same basis as assessments for the construction of the irrigation works by which the lands of the district are irrigated. In all cases where the cost of drainage works shall be apportioned to all the tracts of lands of the district as herein provided, all the provisions of this title applicable to procedure and the confirmation of the apportionment by the court, including the right of appeal, shall be applicable to the apportionment of benefits under this section.
Idaho Code § 43-305