4 Inches Of Rain Is All LA Got Last Year

A pedestrian uses an umbrella on a hot sunny morning in Los Angeles on October 24, 2017. Last year was the third driest since record keeping began in 1877. (Photo by: FREDERIC J. BROWN/AFP/Getty Images)

Last year, Downtown Los Angeles got exactly 4.72 inches of rain.

That's measly! It's smaller than the screen on an iPhone. Less than the length of your sunglasses. Shorter than an average adult hand. And it's 32 percent of what we normally get.

That makes October 1, 2017 through September 30, 2018 the third driest year since record-keeping began way back in 1877.

Only 2001-2002 and 2006-2007 were worse.

Five of the 10 driest water years on record in Downtown Los Angeles have occurred since 2000. Data: National Weather Service.

THE SCARY TREND

You read that chart correctly: the three driest years ever in LA's history have all happened in the 21st century, according to the National Weather Service.

Scientists say drought is likely to become more much common in the future as temperatures rise. That's not only because of a lack of rain — warmer air sucks more moisture from plants and from the ground, intensifying what may already be a dry year.

STORM CLOUDS AHEAD

But climate change is complex. Warmer air, and warmer oceans, can also have the REVERSE effect: intensifying storms. Extremely wet years, like the winter of 2016-2017, are also going to be more likely in the future, according to a study published earlier this year by UCLA.

"In a warmer climate, there is more water vapor in the atmosphere," said David Neelin, a climate scientist at UCLA. "When a storm gets going, air converges at low levels carrying more water vapor with it. With more vapor to dump out, the result is more rainfall."

WEATHER WHIPLASH

Essentially, the system is becoming more volatile, said Neil Berg, an associate director of UCLA's Center for Climate Science.

"We might have the same amount of water over a 20 year period, but it's gonna come in really dry years, followed by a really wet year," he said.

Case in point: the National Oceanic and Atmospheric Administration is predicting "above normal" precipitation for Southern California this winter. That's partially because there is a 70 percent chance of an El Niño event — a band of warm water in the Pacific Ocean that often means a wetter winter.

SO MUCH FOR BUY LOCAL

Los Angeles imports water from two sources: the Metropolitan Water District and the LA aqueduct, which is owned by the city. A small percentage of drinking water comes from recycling and local groundwater. Source: LADWP UWMP 2016.

Mayor Eric Garcetti has a goal of getting half of the city's water from local sources by 2035. Currently less than a quarter of LA's water supplies are local, a term that includes underground aquifers, captured stormwater, and recycled drinking water.

Long-term volatility could make it hard for the city of LA to meet that goal.

That's because if it doesn't rain, aquifers don't recharge, and runoff doesn't rush down dry river beds, where we can capture it and store it underground.

And when it does rain hard, infrastructure for capturing stormwater is often overwhelmed.

"Being reliant on your own resources is a great idea," Berg said, "but I do think that when you're having more extreme dry and wet years for this region, that does complicate just relying on your local resources."

This story is part of Elemental: Covering Sustainability, a multimedia collaboration between Cronkite News, Arizona PBS, KJZZ, KPCC, Rocky Mountain PBS and PBS SoCal.


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