Six years ago, Don Cameron, the general manager of Terranova Ranch, southwest of Fresno, Calif., did something that seemed kind of crazy. He went out to a nearby river, which was running high because of recent rains, and he opened an irrigation gate. Water rushed down a canal and flooded hundreds of acres of vineyards — even though it was wintertime. The vineyards were quiet. Nothing was growing. “We started in February, and we flooded