Bob:

I'm in Austin as well and I just built my pond (4x4x2, 150 g) on top with a smaller (8x4x3, ~400 gallons)on the bottom with about 20' of stream/waterfalls using a 3900 gph pump. It's kind of scary how much water evaporates, makes you think you have a leak or something, hopefully I don't. I lose about 1/2 in. overnight and about another 1" during the day. I do have a lot of splash though.

Is this too much? I'm still paranoid so I keep checking the overlaps of the liner.

Nik