S.D. Codified Laws § 46-7-1
The owner of any works for storage, diversion, or carriage of water which have a capacity in excess of the needs of the owner for lawful application of water to beneficial use may be required to make the excess capacity available, at reasonable rates, to any person entitled to use water for beneficial purposes. However, the excess capacity need not be made available if the use of the excess capacity would unreasonably damage existing works or require substantial modification of the works. Upon petition, the Water Management Board may determine if excess capacity can be used without unreasonable damage to existing works or without requiring substantial modification of the works. If the board's findings are positive, it may establish reasonable rates and may set the compensation to be paid to the owner for damage to existing works. This section does not obligate any person to continue operation of any works.
SDCL 46-7-1