Mont. Code Ann. § 85-8-802

Ten percent of the adult owners or legally authorized agents or representatives of minor owners of lands within any drainage district heretofore created and organized and in existence on February 27,1925, may file a petition with the proper district court to have such district divided into divisions. Such court must thereupon make an order setting a day for hearing such petition and cause a copy of such order to be served on each of the commissioners of such district at least 5 days before the date set for such hearing. On the day fixed in such order (or on any day to which such hearing may be regularly continued) the court must hear such petition and, after such hearing, must make an order dividing such district into three divisions, as nearly equal in area as possible.