S.D. Codified Laws § 46A-4-50
The boundaries of any irrigation district organized under the provisions of this chapter may be changed, and tracts of land included within the boundaries of the district at or after its organization under the provisions of this chapter may be excluded from the district in the manner prescribed in this chapter. However, neither a change of boundaries of the district nor an exclusion of lands from the district may impair or affect its organization, or its rights in or to property, or any of its rights or privileges, of whatever kind or nature. No such boundary change or exclusion of lands may affect, impair, or discharge any contract, obligation, lien, or charge for or upon which the district is or might become liable or chargeable, had such change of its boundaries not been made or had not any land been excluded from the district.
SDCL 46A-4-50