California saw this drought coming. Even if people in the state didn't know it would be this bad — now the worst in recorded history — they've known that dry years are inevitable and had all sorts of ideas for how to deal with them.

But for all that planning, California's current drought has been a disaster. Reservoirs are drying up. Crops are wilting in the fields. For the first time ever, towns and cities will face a mandatory 25 percent cut in their water use.

The underlying problem is bigger than almonds or golf courses

The problem isn't that no one foresaw the drought. The problem is that no one has been able to solve an underlying issue that is simultaneously less scary and also much harder than a dry spell: California's convoluted water system and intractable water politics.

Designed piecemeal over the last century, going back to a time when Los Angeles had one-sixth its current population, California's system for managing water doesn't just make it tough to deal with shortages — in some ways, it encourages inefficiencies and waste. This is partly an engineering issue and partly a political one, but it's become a huge dilemma for a state struggling to adapt to unprecedented drought.

Much of the bickering today around California's water crisis can trace back to this underlying systemic issue. Many people accuse farmers — especially its almond growers and cattle ranchers — of using too much water. Farmers, in turn, blame environmentalists for placing undue restrictions on water use. Others fault golf courses and overwatered lawns. Economists say California could better manage its water if only it was priced properly.

There's some truth to all these points. But it's worth understanding California's incredibly complex water system in order to grasp why all these conflicts have arisen — and why fixes are so difficult.

1) California's water comes from the north and is used in the south

Perhaps the most fundamental water fact about California is that, historically, water was extremely scarce in the southern two-thirds of the state. The vast majority of precipitation occurs up north, mainly in the winter.

So, during the 20th century, both the state and the federal government built an elaborate system of canals, aqueducts, and reservoirs to bring water south:

Key parts of this system include:

The Central Valley Project, built by the federal government in the 1930s, brings water down to the Central Valley, which has now become a key hub for California's agriculture.

The State Water Project, built by the state in the 1960s, brings water down to San Francisco and Los Angeles, as well as to the Central Valley.

The Colorado River Aqueduct, built in the 1930s, brings water from the Colorado River to southern California. Water from this river is divvied up between California, Wyoming, Nevada, Utah, Colorado, New Mexico, Arizona, and Mexico according to rules dating to 1922.

Today, 75 percent of California's water supply originates in the northern third of the state, above Sacramento, while 80 percent of water users live in the southern two-thirds of the state. The system that makes this possible operates under a complex thicket of rules, managed by federal, state, and local agencies. But, for decades, it helped California bloom.

2) California's water supply can fluctuate by 40 million acre-feet depending on the year

Rainfall and snow have never been constant in California. In any given year, some part of the state is usually in drought. And for a long time, the water system has been able to deal with at least some oscillations.

In an average year, California gets about 200 million acre feet of water from rain, snow, and imports from other states. Roughly half of that is absorbed by native plants, evaporates, or flows into the sea. The other half is managed by humans — in the water system described above — and it's known as the "developed water supply."

However, this precise amount can vary a lot year to year. The Department of Water Resources refers to "dry years," "average years," and "wet years." Historically, the state's developed water supply can fluctuate between roughly 60 million acre-feet in a dry year and 100 million acre-feet in a wet year:

The importance of different sources also shifts. During dry years, delivery systems like the Central Valley Project and the Colorado River Project are called on to transport more water to cities and farms. Farmers also compensate by relying more heavily on water pumped from underground aquifers during dry years (they then let those aquifers recharge in wet years).

3) California is now suffering the worst drought in history, and its water system is cracking under the stress

Now, however, this system has reached a breaking point. This current drought, which started in 2012, is worse than anything California has endured in its history. Virtually the entire state is facing "severe," "extreme," or "exceptional" drought:

Not only has precipitation been abnormally low, but the state has endured exceptionally warm temperatures that have sped up evaporation. Global warming likely deserves some blame for that latter aspect.

According to one metric from the National Weather Service, those two factors have combined to make this the worst dry spell since at least 1895 — and likely long before:

The strains on the system can be seen everywhere. Reservoirs like Lake Oroville and Lake Shasta, key nodes in the state's water storage and delivery system, have been well below capacity. The Central Valley Project has been reducing water deliveries to users — and even cutting off some farmers. Last year, farmers had to let 400,000 acres go fallow and have been depleting underground aquifers to compensate for the lack of surface water.

This winter, things got even worse. One-third of California's water supply typically comes from snow on the mountains that melts in the spring. But thanks to a warm winter, little snow fell this year. On April 1, snowpack in the Sierra Nevada mountains was just 6 percent of normal. That's absurdly low: the previous record for this time of year was 25 percent, set in 2014.

That means there's going to be a huge water crunch in California this summer. Roughly 41 percent of California's farmland will face deep water cuts, and 620,000 acres are expected to go fallow, with economic losses of some $5.7 billion. That sets the stage for fierce conflicts between different users.

4) Humans use over half of California's developed water supply (and leave the rest in the environment)

California's developed water supply is divided between three main sectors. In an average year, about 40 percent of the state's developed water is used by agriculture. Another 10 percent is used by towns and cities. (The oil and gas industry uses some water for fracking, but a negligible amount.)

The other 50 percent is generally left to protect and restore the environment. That is, the water is allowed to keep flowing through streams and watersheds in order to maintain ecosystems, keep the fish alive, preserve water quality, and so on. As the chart above shows, however, the precise amount left over for this purpose fluctuates a lot between wet and dry years. During droughts, there's far less water flowing through California's streams and rivers.

In some places, rules prevent humans from taking every last drop of water

More than half of this "environmental" water is located up in the rainy north, remote from population centers and not really usable. But there are also places in California where laws prevent cities and farms from taking every last drop of water. Sometimes this is done to benefit other humans further downstream or maintain water quality. Sometimes it's done to protect fish or other species.

This can, at times, lead to conflict. In 2007, for example, a federal court ordered the Banks pumping plant near Livermore to reduce water deliveries to towns and farms to ensure there was enough water flowing in the Sacramento–San Joaquin Delta for the endangered Delta smelt.

The current drought will likely lead to new battles. Some farmers, faced with shrinking water deliveries, have expressed frustration at limits placed on water use by various environmental rules. Environmentalists, meanwhile, point out that some streams and ecosystems are now facing dangerously low water levels, putting fish and other species at risk of extinction.

5) Farms account for 80% of water use (cities are 20%)

If you're looking at human consumption, then farmers are the dominant water users in the state. There's a reason for this: California plays a pivotal role in US agriculture.

The state is responsible for roughly one-third of the country's vegetables and two-thirds of its fruits and nuts. The fertile soil and temperate climate are ideal for things like pistachios, broccoli, tomatoes, and lettuce.

The crops that get the most attention are almonds, which now account for roughly 11 percent of California's human water use — especially since almond consumption is absolutely soaring. But a lot of water is also used for alfalfa, grown as feed for cattle (14 percent), pasture for livestock (9 percent), rice (7 percent), and so on.

6) Complex laws govern how farmers get water — and when they get cut off

California's farmers get their water from a couple of different places. Some rain falls directly on crops. But a huge chunk of water for irrigation comes from California's elaborate delivery system, which is fed by both rainfall in the north and melting snow from the mountains.

The CEntral Valley Project is now cutting some farmers off

The laws around which farmers get how much water from these systems are absurdly complex and are often based on historical rights. There are "riparian rights," which gives access to those who are physically next to waterways. There are laws of "prior appropriation," which give senior rights to those who first diverted the water for beneficial use, tracing back decades. For those who have water rights, the price is usually quite low.

During dry years — like the current drought — those water rights become important. This year, for the second year in a row, the federal Central Valley Project will initially deliver no water to farmers with junior rights. Some users will get their full allotment of water; others will get none. That's why some farmers are expected to let some 650,000 acres of land go fallow.

But not everyone can let their land go fallow. Almond farmers, for instance, can't just skip watering their trees for a year; the trees will die. That's why many farmers, particularly almond growers, have seeking out another controversial source: groundwater.

7) In drought, farmers start depleting groundwater — a risky move

When there's less surface water during droughts, many farmers shift instead to pumping water from underground aquifers — water that's built up over many decades.

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. During the current drought, one 2014 UC Davis study found, California's farmers have been replacing about three-fourths of lost rainfall with groundwater.

As a result, satellite surveys have shown, California's groundwater has been vanishing at a shocking rate:

This groundwater pumping has helped farmers stave off immediate disaster. But there's a longer-term problem here. These underground aquifers aren't easily refilled, since they were built up over many years. 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 crucial buffer against both this drought, if it persists, and future droughts.

California is finally starting to address this problem, but only sort of. Last year, amid heavy opposition from agricultural interests, the state legislature approved new restrictions on groundwater pumping. But some experts have lamented that these restrictions are fairly flimsy, and will only be phased in gradually between 2020 and 2040.

8) Farming in California is getting more efficient — but still has some big problems

The share of California's water used for agriculture has actually declined since 1980 — in part because farmers are using more efficient irrigation techniques and planting crops that generate more value with less water. In the current drought, many farmers are genuinely working hard to conserve.

That said, as a recent paper co-authored by Robert Glennon of the University of Arizona details, there are still a fair number of odd inefficiencies and weird incentives around agricultural water use, in part because of the elaborate rules around usage and in part because water is often artificially cheap.

Rules against water trading can create perverse incentives

An example: In the summer, when temperatures soar and water is scarce, many farmers in southern California still use enormous quantities of water to grow alfalfa, a fairly low-value crop that gets shipped abroad for use in dairy industries. (Remember, 14 percent of California's water use goes toward alfalfa.)

Why is that? In some cases, farmers have to use the water they get or they lose the rights to it. So they may as well grow something. Plus it's not always easy for farmers to sell their water rights to other people who might find better use for it — there are still quite a few barriers standing in the way of routine water trading. So farmers use cheap water to grow alfalfa, even though it's sort of a waste.

9) Water prices for farmers vary widely across the state

Water isn't free. But what's striking about California is that the price of water varies wildly from region to region — and is often incredibly cheap for farmers.

Farmers in the Central Coast and South Coast pay roughly as much for water as residential users do. But farmers everywhere else only pay about one-sixth that amount:

Why the disparity? As the Legislative Analyst's Office explains, the South Coast and Central Coast are served by the State Water Project, which has a higher cost of delivery. The other parts are served by federal water systems, which are largely paid off. Complex water contracts also affect the price.

This varied pricing helps shape what crops are grown where. The Central Coast and South Coast have pricier water, so they tend to grow higher-value crops such as artichokes, strawberries, avocados, and citrus (the soil and climate is also right in these areas). In areas where water is cheaper, you're more likely to find lower-value row crops like cotton, corn, or tomatoes.

There are also big differences in water efficiency from region to region for the exact same crop. An acre of tomatoes in the Colorado River region uses twice as much water, on average, as an acre of tomatoes in the Central Coast. Climate conditions affect that, but so do prices.

10) California's households use a lot of water — though they've been cutting back

As we've seen, cities and towns only account for 20 percent of California's human water consumption. But that doesn't mean they're conserving as much as humanly possible, either.

California's per-capita water use is dropping — but it could still fall further

The map above, from the Hamilton Project, is striking. Back in 2005, the average person in California's towns and cities used 124 gallons of water per day — more than twice as much water as the average person in Maine. Why? Lawn watering, mainly. "Whereas residents in wetter states in the East can often rely on rainwater for their landscaping," the report notes, "the inhabitants of Western states must rely on sprinklers." (Within the state, water use varies widely, with residents in Beverly Hills using 165 gallons per day and residents in San Francisco using just 46.)

Now, in fairness, California's per-capita household water use has been declining in recent years — and overall urban water use has stayed flat, even as the population soared past 38 million. That's thanks to measures to promote water-saving technologies, such as restricted-flow showerheads and low-flow toilets. During the current drought, many cities and towns have been cracking down further on lawn watering.

Even so, some water analysts think there's a lot further to go. For reference, California's cities use about twice as much water per capita as Sydney, Australia, which is in a similarly dry climate. Economists also point out that the price of water varies a lot from city to city, with little relationship to scarcity. And wasteful water use is likely to continue so long as water is underpriced.

In March 2015, Governor Jerry Brown announced the first-ever mandatory water restrictions, which will force cities and towns to reduce their water usage by 25 percent in the coming year (varying from town to town). Some water utilities will be encouraged to put "conservation pricing" in place, although many of the cuts will likely come through blunt regulations.

11) California's drought problems could get much worse

Back in 2008, the Legislative Analyst's Office pointed out that over the next few decades, as the population grows, California is on track to face significant water shortfalls during "dry" years, unless major changes are made.

In the ancient past, "Mega-droughts" have lasted for decades

And there's a real risk that global warming will worsen those water woes. As the world heats up, California is expected to face higher temperatures. That means less snowpack in the mountains, more evaporation, and a higher risk of severe droughts in the years ahead.

There's also the dreaded "mega-drought" scenario. Historical evidence from tree rings suggests that in the very distant past, California has endured droughts that lasted many, many decades. It's unclear if the state is currently in such a dry spell. One recent study, however, led by NASA's Benjamin Cook, warned that mega-droughts will be more likely this century if greenhouse-gas emissions keep rising.

The state isn't ready for this. "California has no contingency plan for a persistent drought like this one (let alone a 20-plus-year mega-drought), except, apparently, staying in emergency mode and praying for rain," wrote NASA water scientist and University of California-Irvine professor Jay Famiglietti in a widely circulated op-ed in March.

12) There's no simple solution to California's water woes

Okay, so what's the answer? Let's run down some of the proposed fixes in California so far, none of which fully solve California's water crisis:

Mandatory cuts: Governor Jerry Brown has ordered cities and towns to cut their water use by 25 percent. One flaw? This move does nothing to address agriculture, which consumes four times as much water as urban areas do.

Water-recycling projects or desalination: Back in 2014, California voters approved a $7.5 billion water bond to fund new water recycling, desalination, and drought-preparedness projects. That could help, but those will take time to get underway.

There are plenty of innovative technologies that could help conserve water, though they tend to be quite costly. San Diego is building a desalination plant to make 50 million gallons a day of salty water usable, though it will cost $1 billion, use a large amount of energy, and only supply about 7 percent of the region's water.

Groundwater pumping restrictions: The state legislature has also approved restrictions on groundwater pumping from agriculture, which will help conserve a vital and limited resource. But those won't take effect for another five years and will then be phased in gradually between 2020 and 2040. And even those weak rules were fought by many of California's farming interests.

And what about outside proposals?

Consumer changes: Some people have suggested that California would be better off if we all stopped eating almonds, which are using a ton of the state's water. (And, since almond trees can't be fallowed for a year, they're consuming a lot of that scarce groundwater.) Or perhaps we could eat less meat, which also requires a lot of water. It's true, it'd be a huge boon for the planet if we all ate less meat, but unfortunately neither of those things would fix the complex thicket of rules and water pricing in California that encourage inefficient water use.

Water pricing: Some economists have called for better water pricing to encourage more efficient use of water among both households and farmers. The Hamilton Project has offered some suggestions on how California and the West might do this. The hitch? More efficient pricing strategies aren't always easy to implement, given the complexity of the system. They also don't fully solve the tension between human and environmental uses of water.

Bolster water markets: In a similar vein, the University of Arizona's Robert Glennon has called on California to bolster water markets and allow even more water trading among farmers, improving efficiency. (California already does allow farmers to trade the rights to surface water, although the approval process can be cumbersome.)

It wouldn't take much to have a big impact — if farmers could boost water efficiency by just 4 percent, that would increase the amount of water for cities and businesses by 50 percent. See here for an overview of how California's water markets currently work, and how they might be expanded. Australia has very robust water markets — in which the government buys up water for conservation —though they're also contentious among some farmers.

But if water markets are so wonderful, why aren't they more widespread? Last fall, John Fleck, a journalist for the Albuquerque Journal who does a fantastic job of covering water issues, notes that these proposals keep coming up again and again. But the obstacles are formidable.

"This is not for lack of smart scientists and policy people pointing out that the problem is deeper and requires stronger action," Fleck noted on his blog. "This rather reflects a shortcoming of the political system that has left us at with a sub-optimal equilibrium because of the ability of individual players, acting in their own short-term interest, to block progress toward a more socially optimal solution."

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