Oregon Revised Statutes Water Resources: Irrigation, Drainage, Flood Control, Reclamation § 553.620

(1) A water control district may, in lieu of any or all of the assessments provided in this chapter, levy an ad valorem tax upon all taxable property situated within the boundaries of the district or subdistricts for a purpose or purposes expressed therein. A levy of an ad valorem tax for a given purpose shall not be in addition to any other assessments by a water control district for that purpose.

(2) As used in this section, “purpose” means the type of service to be performed by the district, or subdistrict, as set forth in ORS 553.020 (1) and (2). When the construction of an improvement serves more than one purpose, the cost of construction or the cost of maintenance shall be allocated between the two or more purposes on the basis of engineering studies.