Interesting math, which is stupidly hard to get a grasp on because of dumb imperial units.
Beef turns out to have an overall water footprint of roughly four million gallons per ton produced
"four million gallons".
The cited paper gives the slightly more understandable: beef: 15,400 m^3 / ton
Aargh. Which fucking "ton" is that? I assume they mean "tonne" because everything else in the paper is metric:
So it takes around 15,400 tonnes of water to make 1 tonne of beef.