Idaho Code § 43-308
After receiving a petition signed by the holders of title or evidence of title to one-fifth (1/5) of the lands within the district praying it shall do so, any irrigation district desiring to accept the provisions of this act shall so declare by resolution adopted by majority vote of its directors and spread upon its minutes, and thereupon said district shall cause to be filed with the clerk of the district court of the county in which a greater portion of the lands of said irrigation district are located, its petition praying that the court shall set a day for hearing said petition and on and after said hearing make and enter its order and decree authorizing such irrigation district to perform all of the functions of a drainage district under the laws of the state of Idaho, and that there are lands within said district which need drainage: that there shall be attached to said petition so filed with the clerk of said court a true and correct copy of the petition of the said land owners in this section provided, together with a copy of said resolution of the board of directors of said district.
Idaho Code § 43-308