Policy debates are always easier when there's a clear villain. And as California grapples with a brutal drought, a truly diabolical one has emerged: almonds.

The reasoning is simple: California is facing a water crunch. And the state's almond growers now account for 10 percent of water use in the state — a number that's soaring as people worldwide eat more almonds and chug more almond milk. Almond growers, we're told, now use three times as much water as the entire city of LA. So if everyone switched to other snacks, California would have more water to spare. Right?

Well ... yes and no.

It's true that the rapid proliferation of almond trees — plantings rose 25 percent in 2014 — has created real water problems for California, particularly in the drought-stressed San Joaquin Valley (see map). Almond trees stick around for years and need to be watered constantly. So in a drought, almond growers can't just go without water. Instead, they've been depleting the state's underground aquifers, a huge long-term problem.

At the same time, many of the problems caused by almonds can trace back to California's complex regulations around water, laws that often encourage unsustainable use. Even if we stopped eating almonds tomorrow (or meat, or dairy, or any popular scapegoat for California's woes), those problems wouldn't go away entirely. At least not until the underlying structural issues get fixed.

In theory, there's nothing wrong with growing almonds...

Let's start with a basic point. California has good soil, plus an elaborate system to deliver irrigation water around the state. Under the circumstances, farmers should grow crops. The world needs food. Food is good.

Farmers get a lot of value by converting water into almonds

And in theory, almonds seem like a good choice. Yes, it takes more water to grow an ounce of almonds than it does to grow an ounce of lettuce or tomatoes or broccoli. (Though almonds require far, far less water per ounce than producing beef or dairy does.)

Yet almonds are also more valuable than most other crops. In fact, as Alissa Walker points out at Gizmodo, farmers get more value out of a gallon of water by planting almonds than they do through most other crops. Compare that with alfalfa, which accounts for 14 percent of California's water use and is a much lower-value crop sold as feed to dairy industries abroad. (We'll get back to alfalfa shortly.)

In a perfect world, then, there shouldn't be anything wrong with almond farming. Farmers are turning water into a more valuable commodity, creating income and jobs, some $11 billion in all. Almonds account for roughly 13 percent of California's agricultural water use but 15 percent of the value of California's farm output. This is how the economy grows. Right?

The catch, however, is that we're not talking about a perfect world. We're talking about California. And when almond farming runs into California's byzantine water policies, genuine problems ensue.

The problem is groundwater depletion — which almonds make worse

Farmers in places like the Central Valley have a couple of main sources of water apart from rain. First, there's the surface water that's delivered from rivers and an elaborate system of canals and reservoirs built by the state and federal government over the past century. That surface water is split among farmers according to a complicated set of rules — rules that are often based on historical precedents rather than market prices.

When a drought hits, that surface water gets reduced or cut off for some farmers. The current drought has been so bad that for the second year in a row, the federal Central Valley Project will initially deliver no water to farmers with junior rights. In response, many farmers who might normally grow lettuce or tomatoes or broccoli will let their fields go fallow — 600,000 acres in all.

In a drought, almond farmers can't just stop watering their trees

But not everyone can do that. In particular, almond growers can't skip watering their almond trees for a year. The trees are supposed to last many years, and they'll die without water. That's why growers have been seeking out another, more problematic source of water: groundwater.

Beneath the Central Valley are underground aquifers that have built up over many thousands of years. And, unlike in other western states, the rules on pumping water from California's aquifers have long been pretty loose: anyone can draw as much as they want, as long as it's for a useful purpose.

In the current drought, farmers have done just that. A 2014 UC Davis study found that users have replaced about three-fourths of lost rainfall with groundwater. As a result, satellite surveys have shown, California's aquifers are depleting at a staggering rate:

The issue is especially acute in almond regions — if you compare a map of almond production with a map of aquifer depletion, they line up remarkably well.

This pumping has helped farmers stave off short-term pain. But it's creating a long-term disaster. These underground aquifers aren't quickly refilled, since they were built up over centuries. What's more, as these aquifers get drained, the land above them starts sinking, which means they can't hold as much water in the future. Add it all up, and farmers are losing a key buffer against both this drought, if it persists, and future droughts.

That's the real problem with the almond boom. As the drought hits, many farmers are switching to higher-value crops like almonds in order to get as much value as possible out of their increasingly scarce water. Better technology and efficient irrigation has allowed them to grow almond trees in drier areas and poorer soil, like the west side of the San Joaquin Valley. So far, so good. But all these nut trees need watering — so farmers go after groundwater, and a precious resource vanishes.

So how to fix the problem with almonds?

There are a couple of potential ways to respond to this almond issue:

Option 1: Ban almonds? First, California's lawmakers could, in theory, restrict the production of almonds in California. (Maybe add pistachios, too.) You can find a provocative proposal for an almond ban over at the blog On the Public Record. The pros are that this would be easily enforceable and probably would free up a lot of water. The huge downside is this would prevent farmers from growing a valuable crop that people enjoy eating. Not a great outcome.

California's rules around groundwater are still very weak

Option 2: Regulate groundwater. A second option would be to more tightly regulate groundwater withdrawals. California's legislators made a move along these lines in 2014, when they passed a law that would put the state on a path toward sustainable groundwater use. The hitch? This law gets phased in very, very slowly, and doesn't really put California's basins on a sustainable footing until the 2030s or 2040s. That's not much help in the current drought.

So California could try to revisit the groundwater issue and enact tighter standards to take effect more rapidly. True, this is likely to be controversial and would almost certainly meet with stiff resistance from influential farmers, in part because it could curtail the expansion of almond orchards. (Then again, so would a ban.) But it gets at a key issue — it's not the nuts themselves, but the groundwater depletion.

Option 3: Bolster water markets. In addition to groundwater regulation, California could expand water trading and/or bring the price of water more in line with supply and demand. Robert Glennon of the University of Arizona has argued that water markets are an effective way of managing scarce resources.

Imagine two farmers, a broccoli grower and an almond grower, both with rights to a certain amount of surface water. They have different tolerances for drought. If water becomes scarce, the broccoli grower can let his fields go fallow for a bit. But the almond producer can't do this — his orchards will die.

So there's an opportunity for trade. The almond grower pays the broccoli grower a little extra during wet years. In exchange, the broccoli grower agrees to let his field go fallow during a drought and let the almond grower use more surface water so that his trees don't die. Both sides come out ahead.

California already allows some trading of surface water. But as Glennon notes in this paper, there's room to expand these markets further. Policymakers could create a system to allow similar trades for groundwater, for instance. That might entail putting a cap on total withdrawals from aquifers, but would allow farmers to trade rights. (Arizona does a version of this.)

Better water markets might also help solve the issues around another popular scapegoat: alfalfa. Right now, Glennon notes, even when water is scarce, many farmers in southern California still grow water-intensive but low-value alfalfa shipped to China as feed for dairy cows. But why are they growing such a low-value crop? Partly because those farmers can't easily trade their water rights to other Colorado River users who can find better uses for that water. So they may as well grow something with it.

If groundwater regulation was tightened and markets were bolstered, you'd presumably see a more flexible agricultural system emerge — one where California has a more balanced mix of trees and annual crops like vegetables that can scale back during droughts.

We shouldn't be in a situation of demonizing specific crops

Now, because California's water laws are so complex and reform efforts are so politically contentious — farmers with water rights don't want to give them up — it's natural to think options #2 and #3 above are impossible. Going after almonds is simpler. Consumers in New York or Boston can more easily stop eating almonds than they can push for changes to California's water laws.

That's understandable. Still, it's a little, uh, nuts that we're in the position of demonizing specific crops to help California.

The broader lesson is this: it's not quite right to say California is "running out of water." Rather, it has a finite amount of water combined with rules that sometimes encourage people to use that water inefficiently or unsustainably. If those broader rules and incentives could be fixed, then California would be able to allocate its water to the most productive uses and we wouldn't all have to fret about what snacks we should and shouldn't be eating.

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