And farm where? The aquifer used by most of the midwest is over half drained and can't be replenished. South of there is dessert. North is cold. East is populous and mountainous.
If we made no change other than to stop growing the almonds that we export overseas, that alone would free up enough water to accommodate about 20 new San Franciscos:
I mentioned almonds because California grows so many of them that the total water use of all the state's production outweighs the total for beef, but your point is valid that beef (in terms of water-per-pound-eaten) use even more water. This is another area we could free up the supply for residential use: Let other parts of the country develop stronger cattle industries. Or just let the price of meat go up.
