Earlier quoted context omitted.
I'm a biased vegan but... 802.7 gallons of water for one pound of beef 187.969 gallons of water for one pound of vegetables Agriculture consumes 2/3rds of California's water, most of which goes to growing and feeding farmed animals. Source: http://www.waterfootprint.org/?page=cal/WaterFootprintCalcul... (Used United States for country)
As a biased omnivore, it would probably be a bit more useful to compare the calorie content of 1 lb of beef vs 1 lb of vegetables. I understand the point you're getting at but the bias might be a little bit too strong there.
90% Lean Beef: 798 calories per pound
80% Lean Beef: 1152 calories per pound
Carrots: 186 calories per pound
Potatoes: 354 calories per pound
Using GP's numbers for gallons/pound:
90% Lean Beef: .994 calories per gallon
80% Lean Beef: 1.435 calories per gallon
Carrots: .990 calories per gallon
Potatoes: 1.883 calories per gallon
Much closer than I was expecting. I was also not expecting numbers on the order of magnitude of one calorie per gallon...