S.D. Codified Laws § 9-40-15.1
The governing body of each municipality issuing bonds under this chapter shall establish and collect equitable rates, charges, or rentals for all services and benefits furnished by such sewerage and water facility system or systems or drainage basin utility districts. The rates, charges, or rentals shall be sufficient to produce net revenues adequate to pay the principal of and interest on the bonds issued hereunder as such principal and interest become due, and to create and maintain reasonable reserves therefor. The charges may include a reasonable minimum amount for standby or ready-to-serve benefits and may be based on any factors reasonably related to the character, quantity, and quality of the service or benefits furnished. Rates and charges for sewerage improvements may, but need not, be established as a surcharge on water bills to the extent that the governing body shall determine either that water consumed is a fair measure of sewage produced or that the sewerage improvement prevents pollution of the water supply.
SDCL 9-40-15.1