This beef industry organization cites 3 studies: https://www.beefresearch.org/resources/beef-sustainability/f...

> U.S. specific estimates put beef water use at 317, 441 and 808 gallons per pound of boneless beef when precipitation water is not accounted for in calculations.

So, let's just say around 400 gallons of water per pound of beef if you don't include rainfall use.