Right of appropriation; vested rights protected. Subject to existing rights, and except as otherwise provided in ORS chapter 538, all waters within the state may be appropriated for beneficial use, as provided in the Water Rights Act and not otherwise; but nothing contained in the Water Rights Act shall be so construed as to take away or impair the vested right of any person to any water or to the use of any water

ORS 537.120 — under Chapter 537.