The water evaporation is about 1/4- 1/2" per day depending on the temperature. We averaged the mid 80's in July, and had sun most of each day, and my pond is in direct sun from sun up until sun down.
To answer tadpole, my square footage is about 290.
As a side note, the guy that looks after the pool in our boat marina, says he has never had to add water in the amounts he has in the 5+ years he's been there.
We are going into a bit of a cooling trend in the next week, so I'm hoping the water drop is much less.......I hope it;s not leaking...I've had enough of that scenario.