That's already happening in one of America's breadbaskets, the San Jacquin Valley of California. 
The federal govt is diverting water away from farms to protect a small guppy like fish, the delta smelt. 
  
Produce is already going up. 
I was in the area last week. Stopped at McD's to take a pee.  Across the street, in a town of maybe 5,000, there were at least 100 lined up at a food bank across the street. This is in the middle of farmland.