S.D. Codified Laws § 46A-14-6
The boundaries of a watershed district may be entirely within or partly within a county or conservation district and may include the whole or any part of one or more counties or conservation districts. The land ownerships embraced within a watershed district shall be contiguous. If feasible, the district shall include all territory within the affected watershed or drainage basin, or all territory from which the water from natural or artificial channels finds its outlet through a main stream or channel. However, if the ownership of a parcel of land is not a matter of record in the office of the register of deeds of the county in which the land is situated, or if a parcel of land is not subject to payment of taxes or special assessments, the land may be excluded from a proposed or existing watershed district.
SDCL 46A-14-6