Southern California’s drought emergency is over, but its overall drought may not be.

It depends what you mean by “drought.”

Rain caused flooding across the state and began refilling important water reservoirs last week.

Big snows in the Rocky and Sierra mountains also seem to ensure Southern California’s two largest sources of drinking water – the Colorado River and the rivers of Northern California – will be flush with snowmelt during the year to come.

The Metropolitan Water District of Southern California, which gathers water for 19 million people in the region, expects it can now begin storing water for future years. In recent years, it had been using up its water reserves.

The San Diego County Water Authority, which relies on Metropolitan for much of its water, also believes the region is out of the woods for now.

“As far as this year, 2017, we’re not in a drought emergency,” said the agency’s water resources manager, Dana Friehauf. “You could say we’re in a drought-watch, because we’ve always got to look at the long term.”

It’s still too soon to know if the spell of hot and dry weather that imperiled the Colorado River for 16 years and hit California for much of the past decade is truly over.

We can’t predict the future, for one thing.

But we can’t say the drought is over, in part because we can’t agree on what is meant by “drought.”

President-elect Donald Trump, the California Department of Water Resources, the U.S. Drought Monitor and some top climate scientists all have different definitions.

Precipitation Drought

The easiest way to check for a drought is look outside to see if it’s raining.

Tom Buschatzke, director of the Arizona Department of Water Resources, said that’s how ranchers and dryland farmers define drought – if it stops raining, they feel the pain fast.

That test doesn’t work, though, for city-dwellers in Southern California.

In San Diego, the amount of rain the region’s 3 million people can see from their window is almost meaningless. Only about 5 percent of urban San Diego’s water comes from local rainfall. Most of the rest must travel hundreds of miles from Northern California or the Colorado in a series of aqueducts and pipelines.

Yet, it obviously matters how much precipitation is falling in the Rockies and the Sierras, because the sky over there opens and sends down most of our eventual drinking water.

It’s not just the amount of precipitation that matters, it’s the kind. Snow is good, rain is good, but too much rain and not enough snow is bad. That’s because California’s water infrastructure was designed to gradually capture snowmelt.

Even if we got the same precipitation each year, if it all came at once as rain, we would be unable to capture it. One of the worries about climate change is that it will change this mix of rain and snow, leaving us with too much rain and not enough snow.

This year, if it suddenly became hot and dry and the snow quickly melted, that would also be a problem.

“I’m a little cautious, in that it is a really great start, but we need it to fall through for the rest of the winter,” said Deven Upadhyay, Metropolitan’s water resources manager.

The rain and snow test also doesn’t account for groundwater supplies.

Farmers in the Central Valley have pumped so much water out of the ground that it will take decades to refill those depleted supplies. The recent rains don’t do much to solve that problem.

Socioeconomic and Infrastructure Droughts

Perhaps the most popular way of looking at drought is the U.S. Drought Monitor, according to which 58 percent of the state is in a drought, an area in which 26 million people live. A year ago, 97 percent of the state was in a drought.

Yet, 97 percent of the state was not in danger of going thirsty last year.

“It’s not designed to accurately reflect a state like California with an extensive system of infrastructure that moves water around, and one with high groundwater usage,” Nancy Vogel, a spokeswoman for the California Natural Resources Agency, said in an email.

California, as a wealthy and powerful state, has been able to quench the thirst of two of American’s 10 largest cities – Los Angeles and San Diego – even though both are in semi-arid climates.

The key has been extensive investment in infrastructure to take water from where it is to where it isn’t.

Without those investments, the cities would never have been settled by millions of people. Without the upkeep of that infrastructure, both cities would shrivel or die.

In recent years, San Diego has kept trying to buy its way out of drought. The County Water Authority helped build a desalination plant, which makes seawater drinkable. That plant can generate about a tenth of the water San Diego needs.

But the water must be affordable. For most of us, it is. For some San Diego farmers, the high price of water is crippling their low-margin business.

In other words, sometimes it’s only a drought if you can’t afford to buy more water.

In other parts of California, communities don’t have the luxury of investing so heavily in infrastructure, like the Colorado River Aqueduct, which brings water 250 miles to Southern California, and the State Water Project, which brings water from Northern California, 600 miles away.

In East Porterville or Borrego Springs, there is deep concern about the towns running out of water because their residents can’t pay for new groundwater pumps to get water that is farther beneath the ground than their current wells – distances measured in feet, not miles. The water is just out of reach, but they can’t afford to get it.

Regulatory Drought

Last May, during a campaign stop in Fresno, Trump told a crowd that California had no drought at all.

He was widely ridiculed, but Trump was in fact using a definition of drought that has become vogue among Central Valley farmers.

Trump was referring to restrictions on water for farming due to environmental concerns. Pumps that help move the water to the Central Valley can be turned down if endangered fish are too close, meaning regulation rather than the mere availability of water dictates how much is available for use.

Other water agencies, including the San Diego County Water Authority, have similar concerns over so-called regulatory droughts.

Months after Gov. Jerry Brown ordered Californians to cut their water use by an average of 25 percent, San Diego water officials began pushing a similar point: Do we really need to keep saving water?

They and others have accused the governor of creating an artificial limit on water use in certain parts of California.

Because it built a desalinated water plant and because of the high price it paid to secure new water from the Colorado River, the San Diego County Water Authority had almost enough water to meet demand, even if everybody used as much as they wanted and ignored the governor’s cuts.

Indeed, in order to pay for all the stuff they’d built and bought, the County Water Authority was counting on people to continue using as much water as they had been, so much so that when people cut their use, some of San Diego’s drinking water had to be dumped into a lake.

The We-Can’t-Know-If-It’s-Over Drought

When the governor ordered the cuts, it doesn’t seem he was trying to create a regulatory drought, but rather prepare the state for a true shortage of rain and snow – the sort of drought where the water just isn’t available, no matter how big a straw you have.

Droughts can be slow-motion events, said Frances Malamud-Roam, a co-author of “The West Without Water,” a book on California’s climate history. Between the years 900 and 1,400, there were two 200-year droughts.

But droughts aren’t absolute end-to-end events – they come sprinkled with mirages.

The winter of 2010-2011 was wet, for instance, and looked like it might end a drought that began in 2007. Instead, the state fell right back into another drought that prompted Brown to declare the current state of emergency in January 2014. A decent winter last year relaxed those rules. A better winter this year could end them entirely. But we can’t know yet about where we are in history.

“The paleo-climate records also reveal that it was not at all uncommon to have prolonged droughts that were punctuated by years of extremely high rainfall, leading to mega-floods,” Malamud-Roam said in an email. “So this year’s flooding is likely not signaling the end of the drought.”

Clarification: This story has been updated to clarify that water pumps in the Central Valley are typically turned down to protect fish – they are rarely turned off entirely.

Ry Rivard was formerly a reporter for Voice of San Diego. He wrote about water and power.

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