It takes 1 gallon of water to grow a single almond, according to Tom Philpott, food and agriculture correspondent for Mother Jones and author of "California Goes Nuts." Eighty percent of the world's almonds are grown in California, which is experiencing a severe drought. "If you think about it, what you're doing when you buy produce is you're buying water," Philpott says.

Lynne Rossetto Kasper: Nearly every food crop in California is in trouble with this drought. For instance, one walnut takes nearly 5 gallons of water. Why the focus on almonds?

Tom Philpott: It is a huge crop -- way bigger than walnuts, way bigger than pistachios. When you add it all up, almonds take more total water than any other crop.

The other thing is if you think about lettuce, if there's a drought on, you cannot plant lettuce that year or you can cut back on your plantings of lettuce. You use less water. But if you have a massive plantation of almonds, you can't simply not water them.

It raises demand. It keeps it steady and rising even when there's a drought. That's the main problem.

LRK: How much money does an acre of almonds pay a farmer?

TP: My understanding is that you're talking about $5,000 per acre in revenue. That doesn't account for costs. But $5,000 an acre is a lot of money when you multiply it out. Some of these entities own 20-30,000 acres. You're talking about hundreds of millions of dollars.

Almonds at harvest Harvesting almonds Photo: Kseniya Ragozina / iStock / Thinkstock

LRK: I read that between 2013 and 2014, 48,000 more acres have been put toward growing almonds. This is a lot of money.

But isn't it in the best interest of the growers to figure out every way possible to save water? Because otherwise, eventually this is just going to stop dead. There is not going to be an almond crop.

TP: That's very true, but you've got two things going on here.

One is you've got this common resource. These reserves of water underground are a common resource. If your neighbor is down there with a giant straw sucking it away, then you want to get your straw in there too.

The second thing is that about 70 percent of the almond growers in California are family farms. It isn't just corporations that are growing almonds.

But I also found this influx of money from large investment funds, from hedge funds and from insurance companies that are coming in and buying the land as an investment. It's very attractive to them because California is in a farmland boom; land prices keep going up. Then you get this wonderful income of $5,000 an acre off of it. Their time horizon on their investment might be 10 or 15 years. They're thinking, "Let's keep this land for 10 or 15 years, let's make this income off of the almonds or whatever crop we have on it, and then we'll sell it."

Whereas a family farm also has this interest in getting their straw in the Kool-Aid before it runs dry, but they're also thinking about the long-term health of the land, they're thinking about their kids, they're thinking about future generations. Whereas these companies are thinking in a much shorter time frame.

LRK: Is there any way to grow almonds in California that's sustainable?

TP: The Central Valley of California is an almond-growing paradise. You've got these long, dry summers. You've got these winters that are relatively warm, where it rarely, if ever, freezes. California has this incredible infrastructure for capturing snowmelt in the Sierra Nevadas and bringing it down to the farms. These aqueducts and this massive infrastructure was built in the 20th century.

But the question is: Can it continue expanding at the rate that it is now? At the current rate, I don't think there's any sustainable way to grow almonds. It can't go on for very much longer. As much work as they've put in to make almonds water-efficient, they're growing so many of them that I think they've expanded beyond California's water resources.

I think we'll see a pulling back of them. I don't think we'll see the end of almonds.

Almonds Almonds Photo: Swamibu / Flickr

LRK: All this is happening while almonds are becoming more popular than ever?

TP: Right. Almonds passed peanuts in the past couple years as the most popular American nut. Almond consumption here in the U.S. has more than doubled in the past couple of years. In China in the past 5 years, it has quadrupled. You're seeing this surge in popularity.

LRK: Who controls or regulates water usage in California?

TP: There are two kinds of water in California: There's groundwater and there's surface water.

The surface water is highly regulated. This is the stuff that comes off the Sierra Nevada mountains and goes through these aqueducts. Certain places have strong water rights. Other places have lesser water rights. It's a big, constant battle. But there's nothing more regulated in California than surface water.

"You're looking at a situation where California is going to have less water. I'm wondering where are the vegetables going to come from?"
-Tom Philpott

Groundwater is basically the Wild West. Right now, if you own a piece of land in almost any county in California, you can drop as big of a well as you want. There's this Wild West mentality where everyone's just pumping water like crazy.

It's a fossil resource. It takes hundreds and thousands of years of water dripping down into the soil beneath the rocks to get into these aquifers. We're sucking it dry like it's nothing. In my piece, I talk about how living off the surface water from the snowmelt is sort of like living off of income, but living off the groundwater in the aquifer is like living off of savings. It should be used very carefully. Right now, it's not being used carefully at all, I'm afraid.

At the end of 2014, the legislature finally did something about it after years and years and years of talking about it. They put together a law that is going to force every watershed to come up with a policy on its own to rationally regulate this.

But first of all, it's very far off. It doesn't kick in for several years; then, it gradually kicks in. Second of all, there's a lot of concern that the big landowners who own the most land are going to work the system and still be able to get as much water as they want.

LRK: In looking at all of this material about the amount of water it takes to grow all of these things -- the broccoli, the lettuce, the tomatoes, the almonds, the walnuts -- you look at the produce section with completely different eyes.

TP: That's true. If you think about it, what you're doing when you buy produce is you're buying water. So much of our produce comes from California, and so much of that produce is based on this incredible infrastructure that California built up in the 20th century.

The thing that I'm concerned about is that if you look at the fossil record, it looks like California is going to have less water going forward than it had in the 20th century. Then you add climate change to that -- you get less precipitation, you get less snow to pack the mountains in the winter. You're looking at a situation where California is going to have less water. I'm wondering where are the vegetables going to come from.

What I think is going to happen is vegetable production is going to spread out. We're not going to have it as much concentrated in California, which I think is a good thing down the road. It's part of the local food movement. Part of the goal of that was to spread it out. I think that this drought in California and this over-subscription of the water supplies there is going to be a lever to increase interest in growing vegetables in places like Minnesota in the summer.

Lynne Rossetto Kasper
Lynne Rossetto Kasper has won numerous awards as host of The Splendid Table, including two James Beard Foundation Awards (1998, 2008) for Best National Radio Show on Food, five Clarion Awards (2007, 2008, 2009, 2010, 2014) from Women in Communication, and a Gracie Allen Award in 2000 for Best Syndicated Talk Show.