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We've all heard reports about how California is running out of water, but there is water in California, tons of it deep underground in the Central Valley aquifer, the big underground pool that everyone shares. And there's a race on to get what's left. Stacey Vanek Smith from our PLANET MONEY podcast has the story.

STACEY VANEK SMITH: Mark Watte is a farmer in Tulare, Calif. We're driving across his 3,000 acres of beautiful cotton and black-eyed peas and corn. Watte is a very organized guy.

So is that a to-do list on your steering wheel?

MARK WATTE: It is.

SMITH: There is a lot to do these days. Watte relies on the Central Valley aquifer to water his crops. And the water level in the aquifer is dropping 10 feet a week in some places.

WATTE: This is a pump that's - it should be producing water. It's not. Let's see if there's any water in it. This is a good sound. You'll like this.

SMITH: Watte picks up a rock and tosses it down the pipe.

WATTE: Water.

SMITH: Oh, was that - was there water?

WATTE: That was water, yeah. So there's water down there, but the pump that was here wouldn't reach that water anymore. We have to deepen it.

SMITH: Watte is putting in eight new wells - total cost - almost $2 million. He is locked in an expensive race in the Central Valley to see who can afford to drill deep enough to get to the precious water in the aquifer.

A lot of people have already lost this race, like Karen Hendrickson.

KAREN HENDRICKSON: Our well is dry, so we come here for support on drinking water.

SMITH: How long ago did your well go dry?

HENDRICKSON: It's been a year already.

SMITH: Woah.

HENDRICKSON: Yeah. It's been a year.

SMITH: Hendrickson lives in Porterville, Calif., 30 minutes west of Mark Watte's farms. People on the east side of town have no water. They rely on relief stations like this one in the parking lot of a church. It has portable showers and sinks and hands out bottles of drinking water.

HENDRICKSON: My daughter - she has twins.

SMITH: Oh, baby twins?

HENDRICKSON: Yes, a boy and a girl (laughter), yeah.

SMITH: That must be hard with no water.

HENDRICKSON: Yeah, it is. It's kind of hard.

SMITH: Hendrickson's house used to get its water from a well, a well that reached into the aquifer. But the water level dropped below her well, and she can't afford to dig deeper.

Who can afford to dig deeper? People, like Mark Watte, who grow these.

SMITH: These are the pistachios.

WATTE: Yep. There you can see it's about half developed.

SMITH: It's so green. Why are you planting so many new trees right now?

WATTE: Financially, it's the right decision to make - extremely profitable today, wildly profitable.

SMITH: Really.

WATTE: Yes.

SMITH: Ten times more profitable than other crops. Watte makes $10,000 an acre for pistachios. Most other crops bring in a thousand dollars an acre.

And here is where you see the screwed up economics of drought.

Pistachios, almonds and walnuts need a ton of water. They are some of the thirstiest crops around. Growing nut trees in a drought is harder, and that has helped push the price of nuts way up.

So now farmers all over California's Central Valley are doing exactly what Mark Watte is doing - ripping out their other crops and planting nut trees. James Famiglietti is a water scientist for NASA.

JAMES FAMIGLIETTI: It's a real nut rush.

SMITH: A nut rush.

FAMIGLIETTI: And it's a real nut boom.

SMITH: So basically, as water runs out, farmers are planting crops that need more water.

FAMIGLIETTI: That's right.

SMITH: Hedge funds and big banks have started buying California farmland and planting almond and pistachio trees. A lot of them reach out to Famiglietti to ask him, is this a good time to get into the nut-growing business?

FAMIGLIETTI: I generally don't respond. I don't want to encourage someone to go make a short-term investment that would use up a lot of water.

SMITH: Crops that don't need much water don't bring in much money. If you're running a farm, there's no way you can pay hundreds of thousands of dollars to drill a deep well and pay for it with draught-friendly crops. I asked Mark Watte, the pistachio farmer, about this.

Should you be planting something like flaxseed or safflower here instead of pistachio trees?

WATTE: (Laughter). Oh, I - should I be planting it? I don't know. I mean, we're trying to make money here.

SMITH: If Watte were to cut back his water use, he would just lose out. His neighbors would suck up that water. Hedge funds would suck up that water.

The result of this is that everyone is using more water, planting more nut trees, drilling deeper wells. Wells in the area used to be around 200 feet deep. Now many go down 2000 feet.

James Famiglietti, the water scientist, says at this pace, the aquifer will last another 60 years, a hundred years at the most. In the meantime, the water level keeps dropping, wells keep drying up. Mark Watte shows me one that's on the brink.

WATTE: This is a pump that was put into service in 1946, and it is now surging, which means the equipment that's lifting the water is right at where the pulling water level is. And I expect a week from now, it'll be dry.

SMITH: What does it feel like to see it doing that?

WATTE: I purposely don't drive by it, and when I do, I look the other way.

SMITH: Watte thinks things will turn around. He says there's still a lot of water in that aquifer. He thinks it'll rain next year. Stacey Vanek Smith, NPR News.