S.D. Codified Laws § 46A-1-37
The district may covenant that if any of the bonds issued under this chapter remain outstanding and unpaid, the district will not, except upon such terms and conditions as may be determined, voluntarily create or cause to be created any debt, lien, mortgage, pledge, assignment, encumbrance, or other charge having priority to the lien of the bonds issued under this chapter upon any of the income and revenues derived from all revenues pledged pursuant to § 46A-1-33, or convey or otherwise alienate any project or the real estate upon which the project is located, except at a price sufficient to pay all the bonds issued for the project then outstanding and interest accrued on the bonds, and then only in accordance with any agreements with the holder of the bonds.
SDCL 46A-1-37