ORS 547.425: Prohibited practices.

No person shall: (1) Throw, dump or place or allow to be thrown, dumped or placed, any rubbish, refuse or any article or thing in any ditch, lateral, canal, slough, waterway or conduit used as a part of or in connection with any drainage works or drainage plant or drainage system or any waterway under the control of any drainage district lying west of the Cascade Mountains; or (2) Befoul or pollute or allow to be befouled or polluted any such ditch, lateral, canal, slough, waterway or conduit; or (3) In any manner obstruct or permit to be obstructed by stock any such waterway, canal, ditch, lateral, slough or conduit.