I'm back to help with some other parts.
1. Depth will have little affect on the evaporation rate. Evaporation rate is enhanced by amount of exposed water surface, increased air temperature and increasaed wind speed.
2. The depth of your soils before you hit rock may predetermine your pond depth.
3. I disagreee somewhat with Bob about tree roots not affecting the betonite seal. They will have a big impact on the seal if they penetrate the seal. Also, I have seen roots extend WAY BEYOND the drip zone of the tree canopy. As much as three or fout times further than the drip zone. Some tree species can send roots farther out from the trunk than others. Amazing, and I would not have believed it unless I saw it. One inch dia roots embeded in pond wall that was 50' to 60' beyond the branches of large cottonwood trees.
