Idaho Code § 43-1323

The effective date of the partition of the existing district into two (2) districts shall be as of the date of the order of the board of county commissioners. Following the effective date of the partition order by the board, the newly partitioned irrigation district shall immediately undertake to reorganize, elect officers as set forth in section 43-301, Idaho Code, and exercise all powers and duties of an irrigation district. Any appeal from, or judicial challenge to, the order of the board partitioning the irrigation district must be brought in the county where the board sits within ninety (90) days from the effective date of the order or be forever barred.