ORS § 545.097
The boundaries of any irrigation district organized under the Irrigation District Law may be changed, and tracts of land that were included within the boundaries of the district at or after its organization may be excluded from the district in the manner prescribed in ORS 545.097 to 545.126. However, a change of the boundaries of a district resulting from exclusion of lands from the district shall not impair or affect its organization, its right in or to property or any of its rights or privileges of whatever kind or nature. Exclusion of lands from the district shall not affect, impair, or discharge any contract, obligation, lien, or charge for or upon which the district would be liable or chargeable if the change of its boundaries had not been made, or if land had not been excluded from the district.
ORS 545.097