Iowa Code § 468.305
Whenever one or more drainage districts in one county outlet into a ditch, drain, or natural watercourse, which ditch, drain, or natural watercourse is the common carrying outlet for one or more drainage districts in another county, the boards of supervisors of such counties acting jointly may by resolution, and on petition of the trustees of any one of such districts or one or more landowners therein, in either case such petition to be accompanied by a bond as provided in section 468.270, must initiate proceedings for the establishment of an intercounty drainage district by appointing commissioners as provided in section 468.271 and by requiring a bond as provided in section 468.270 and by proceeding as provided by subchapter II, part 1, and all powers, duties, limitations, and provisions of this part and subchapter II, part 1, shall be applicable thereto.
Iowa Code § 468.305
89 Acts, ch 126, §2