In my mind (uh oh, this could be a mistake), full pool in any BOW is determined by the point at which it begins to exit, regardless of the method used to control the exiting water.
When my pond's overflowing the surrounding levee's, I've been saying it's "above full pool". When it evaporates down to the original ground level, I say it's "down to full pool". Now I can't enjoy thinking I have extra water, thanks to you!
