Ah yes; Post, Oregon. The exact geographical center, of our fine state. The Crooked River flows, right through there. But it's largely private land.
I may be mistaken; but I think that Horse Heaven Lake is also private (but again, I am not 100% on that one).
I've been told, by another OFFER, that all 3 of the Merwin Lakes, way out Hwy. 380 are all private. There's really nothing past that, until you hit the John Day River in Eastern Oregon.
Have you thought about Ochoco, or Prineville, Reservoir back to the west?