S.D. Codified Laws § 46A-14-73
The managers may enter into contracts or other arrangements with any agency of the United States government; with persons, railroads, or other corporations; with public and municipal corporations and the state government of this state; or with drainage, soil and water conservation, conservancy, sewer, park, sanitary, reclamation, public power, public power and irrigation, watershed, or other improvement districts, in this or other states, for cooperation, or assistance in constructing, maintaining, using, and operating the works of the districts, the waters of the districts, or in minimizing or preventing damage to the properties, works, and improvements of the districts from soil erosion; or for making surveys and investigations or reports on the surveys and investigations. However no contract or agreement for purposes of implementing the general plan of improvements that will require the levy of increased taxes or assessments may be signed by the managers without submitting the increased taxes or assessments to the eligible voters of the watershed district for approval.
SDCL 46A-14-73