> Basically a 100' square catch basin on the roof of the building would provide all the water they need. Noise.
Which raises the question: Why don't they just do that? I'd imagine it would be less effort to process, and even though you do need to have a buffer against low rainfall periods, water is one of the easiest things to store.
O, I agree it's Noise. However, the reason they don't use a catch basin / just pay for it is Atlanta's high average humidity. There are going to be days where little water is going to evaporate in those cooling towers and most of their energy is going to simply raise the temperature of a large volume of water. So, having access to say 100 times the flow they need is vary helpful.
I see that Atlanta rainfall is about 48" (122cm) a year.
422 gallons * 24 * 365 (* 3.785 litres/gallon) * 100 cc/L == 1.4e9 cc/year.
So converting to rainfall area: 1.4e9cc/122cm = 1148 m^2
Basically a 100' square catch basin on the roof of the building would provide all the water they need. Noise.