I would be loathe to replace the water for a number of reasons. Out here we live in an environment where neighbors call the police on kids running a slip and slide in their own backyard. I wish that was an exaggeration or fabrication, but it happened to us when a nosy neighbor followed the wetness in the gutter to the property. Also, water can be very expensive with penalties attached for using over a baseline amount or for failing to meet your mandatory 10% reduction.
Filling a 20,000 gallon pool uses as much water as our household would normally take 6 months to use. I've toyed with directing all the raingutters into the pool and use that to keep the salt buildup to a minimum. This last year we got 7 inches of rain, so that would have given me about 11,500 gallons of fresh fill.
The city doesn't care that we've cut the water use on this property by over 90% from the previous owners. Every time they declare a drought you have to cut the same as the neighbor who's still using ten times as much as you do.