SDCL § 46A-10A-9: Joint drainage efforts by counties.

The boards or commissions of two or more counties may cooperate on drainage. Expenses incurred in connection with joint efforts, including contracted services, shall be shared equitably per agreement among the counties involved. Promotion of regional drainage projects, coordinated drainage areas and drainage patterns or schemes, including passage of compatible ordinances and resolutions in adjoining counties, is the primary but not exclusive objective of joint efforts.

Source: SL 1985, ch 362, § 9.