Tex. Water Code § 55.165

The board may include in the plans of the district the necessary drainage ditches, or other facilities for drainage, and levees for the protection of land in the district. The district may purchase all or part of any system belonging to a drainage district. However, the purchase contract shall provide for paying or assuming the debts of the drainage district, and the amount of the debts paid or assumed shall be considered in determining the bond-issuing capacity of the district.