Mike , in the California summer most ponds and swimming pools drop a good 4 inches a week.I have a fill line to my pool and a ground water well to our pond ,which is on 20 acres about 15 min. from our house. In the summer I go there 2 to 3 times a week to fill the generator with gas at $14 per pop. .Is it worth it? Every penny!Unless you are blessed with a year around creek or spring and want a full pond ,evap. is just one more thing we have to deal with. But in my opinion, its worth it. I saw the pics of the pond when full and it's awsome. Kevin