[brownbat]

A little over 3 feet.

http://www.wolframalpha.com/input/?i=(40,000+cubic+kilometre...

To skip ahead, the Great Artesian Basin, the largest artesian basin in the world, would be just over 5 feet.

http://www.wolframalpha.com/input/?i=(64,900+cubic+kilometre...

https://en.wikipedia.org/wiki/Great_Artesian_Basin

[droopyEyelids]

How much fracking liquid could we pump in there and remain profitable?

[brownbat]

You're pumping in what's (loosely) soapy water to extract water. And in places where there's mostly positive pressure anyway.

None?