S.D. Codified Laws § 47-21-72
A cooperative shall be operated on a nonprofit basis for the mutual benefit of its members and patrons. The bylaws of a cooperative or its contracts with consumers shall contain provisions relative to the disposition of revenues and receipts necessary and appropriate to establish and maintain its nonprofit and cooperative character. In addition to provisions of the bylaws relative to the disposition of revenues and receipts, the board of directors of the cooperative before allocating and crediting margins to its patrons may, by resolution, provide for the adoption of margin stabilization plans, revenue, or expense deferral plans or other plans that provide for the retention of revenues and receipts in excess of those needed to meet current losses and expenses. Reasonable reserves may be created by the cooperative for payment of the incremental cost of electric power and energy purchased by the cooperative for resale to its patrons.
SDCL 47-21-72