Is animal agriculture really a big deal for water use?
Short answer: Yes. A kilogram of beef carries a ~15,400-litre water footprint, and agriculture takes about 70% of all the fresh water humans withdraw.
Most of beef's footprint is rain (green water), not tap water, and even after you correct for that, animal products still sit far above plant foods on every measure.
Mekonnen & Hoekstra (2012), global averages
The objection
“Those 15,000-litre beef figures are propaganda, most of it is just rain that would have fallen anyway.”
The answer
Half right. Most of beef’s footprint is green water, rain falling on pasture and feed crops. A critic is correct that it isn’t all water out of a tap, and this site won’t pretend otherwise.
What survives the correction is the part that counts. Even on the stricter measure, actual freshwater withdrawals from the rivers and aquifers we compete over, animal products still cluster far above plant foods. The arithmetic is plain: raising the animal means watering everything it eats for its entire life and then keeping a slice of it as meat, so every bit of feed-conversion waste is wasted water too.
Zoom out and it gets worse. Agriculture takes roughly 70% of global freshwater withdrawals, the largest single use of water on Earth, with livestock and feed a major share. Quantity is only half the damage. Manure and fertiliser runoff make animal products the dominant driver of eutrophication, the dead zones choking rivers and coastal seas (Poore & Nemecek 2018).
Correct every exaggeration, grant every caveat, and the conclusion holds: animal products are the most water-expensive way humans feed themselves.