S.D. Codified Laws § 46A-3A-16
After a water development district has been established pursuant to the provisions of chapters 46A-3A to 46A-3E, inclusive, any county, township, or group of townships contiguous to the external boundary of the water development district may be added to and become a part of that water development district by an affirmative vote of a majority of the votes cast on the question in the area proposed for addition, if the board of directors of the water development district to which any addition is to be made by resolution advises the Board of Water and Natural Resources that the water development district board favors the addition. Any county or that entire portion of a county included within a water development district may be withdrawn from a water development district by an affirmative vote of a majority of the votes cast on the question in the county proposed for withdrawal. Proposals for additions or withdrawals shall be in the form of a written resolution or petition to the Board of Water and Natural Resources.
The resolution shall be approved with an affirmative four-fifths vote of the governing body of a county.
The petition shall be signed by a number of qualified voters in the area proposed for the addition or withdrawal equal to at least five percent of the number of votes cast within the area in the most recent gubernatorial election. The county auditor in each county where a petition is circulated shall verify the signatures on the petition.
The resolution or petition shall include a statement whether the election is for the purpose of becoming a part of an existing water development district or withdrawing from an existing water development district and a statement describing the purpose of the action. The resolution or petition shall be presented to the Board of Water and Natural Resources not more than one hundred twenty days nor less than ninety days before a regularly scheduled general election. Upon receipt of the resolution or petition, the Board of Water and Natural Resources shall call an election on the question of whether the addition or withdrawal should be made. The election shall be held in conjunction with the next regularly scheduled general election.
SDCL 46A-3A-16