A decade or so ago, Blue Diamond Growers, the co-op that represents half the almond farmers in California, ran a series of brilliant TV ads. In one, a weather-worn farmer buried to the chest in almonds pleads: “A can a week, that’s all we ask.”

In fact there never was a nut glut: California farmers can’t seem to grow enough almonds. Consumers the world over are scrambling for every tin they can get. They’ve been informed that the almond is a compact protein source with many other health benefits and no apparent downside.

But now California is in the fourth year of severe drought, and it’s the farmers who are scrambling: They’re spending huge sums on any available water to keep