I was replying to the parent on Google not being industry leading efficient and especially comparing to the Yahoo Lockport DC.

But you're right, regarding to water usage we don't publish numbers (nor does anyone else afaik, I haven't found any WUE number for e.g. Amazon, Yahoo, Facebook...) so it's difficult to compare this to others.

I am however confident that a lot of things have been considered and this was the best option, we have imho a good track record trying to do the best for the environment, a lot of attention is being paid to this internally. E.g. everything running on green electricity, which is not the cheapest.

I won't dispute you've had a good track record in the past, but past performance doesn't predict future results, as evidenced here. I understand and appreciate why you're doing it, but I can't simply accept you trying to sweep this DC under the rug. If what the original story said is true, the SC DC is an environmental albatross and you all should hang your head in shame, especially based on past wins in this area. I can not share your confidence that using millions of gallons of drinking water per day for cooling "was the best option" (unless of course you meant to add the words "to our opex" after it).

You are correct, PUE only looks at power efficiency, the metric Google uses for water is WUE.

Also, like you said, these metrics only take into account the efficiency of the DC but fail to measure their ecological footprint.