Oregon Revised Statutes Water Resources: Irrigation, Drainage, Flood Control, Reclamation § 540.710

No person shall willfully open, close, change or interfere with any lawfully established headgate or water box without authority, or willfully use water or conduct water into or through the ditch of the person which has been lawfully denied the person by the watermaster or other competent authority. The possession or use of water when the same shall have been lawfully denied by the watermaster or other competent authority shall be prima facie evidence of the guilt of the person using it.