S.D. Codified Laws § 46A-14-37
Before May first of each year, on dates established by the managers, an annual meeting of the district shall be held during which the eligible voters of the district shall elect, by ballot, under the direction of the secretary of the district, managers to replace those whose terms have expired. At the first annual election, if the board of managers has three members, one shall be elected for one year, one for two years, and one for three years, and thereafter one shall be elected annually for three years. If the board of managers has five members, at the first annual meeting one shall be elected for three years, two shall be elected for two years, and two shall be elected for one year, and thereafter at the annual meeting the terms of those expired, shall be elected for three years.
SDCL 46A-14-37