When most Americans think of U.S. dairy, they picture cows roaming on the verdant pastures of Wisconsin. But in reality, they should replace that image with the tawny fields of California, the largest dairy producing state. California produces more milk and cheese than anywhere else, including Wisconsin, the second biggest producer. California is in the middle of a megadrought, and dairy cows need loads of water. Some of that water is for the animals to drink and wash, but most of the water consumed by dairy is connected to what cows eat, in the form of feed and forage. Much...