Hey Dennis!
You're a real Devil's advocate eh!!!
Here's a way to get around evaporation - mark your water line in the bucket and refill as necessary. This weekend, refilling probably would have had to happen every 10 minutes, I know that the level of my beer was dropping at a seriously fast rate due to all this heat and humidity!!

Rotating laser levles with the receiver unit are the best, that's how I did my pool.