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Here’s A Tool To Track California’s Drought

DATA SOURCES: Rainfall data comes from a weighted average of 96 weather stations throughout the state. Snowpack data represents the average of three different multi-station measures of the northern, central and southern Sierra snowpack. Scripps Institution of Oceanography researchers, through the California Nevada Applications Program RISA and the Center for Western Weather and Water Extremes, helped compile the data.

Is this year's El Niño going to be a real drought-buster for California? Over the next few months, KPBS will be tracking rain and snow throughout the state to find out.

After four years of drought, California desperately needs winter to come bearing gifts of rain and snow. Could this year's El Niño prove to be a drought-buster for the state? In the coming months, KPBS will be tracking rain and snowfall throughout the state to find out.

El Niño is a periodic formation of warm water in the tropical Pacific Ocean that could funnel many storms toward California in the near future. Experts are calling this year's El Niño one of the strongest on record, meaning San Diego could be in for a very wet winter.

Strong El Niños in 1983 and 1998 delivered well above average rain and snowfall throughout California, including northern parts of the state, where precipitation is most needed to replenish California's water supply.

"Every El Niño is a different shape, size, color," said Scripps Institution of Oceanography climate researcher Dan Cayan. "And we'll see. But those large events give us some hope that we will see the moisture being delivered in the water-bearing areas of the state."

Cayan said California is unlikely to make up four years of missing rain and snow in one wet season.

But, he said, this year's El Niño could make a dent in the drought if it maintains its strength. It will have to improve on typical El Niños, which often drench Southern California while leaving the rest of the state parched.

Cayan said the moment of truth is approaching. California's wet season begins in October and runs through the beginning of April.

"It's during that period of October through April that we achieve the lion's share of precipitation here," he said. "Probably more than 80 percent."

With that time frame in mind, KPBS is launching an interactive tool that will track rain and snow throughout the state over the next few months.

We'll check in with the KPBS Drought Tracker regularly to get updates on how this year's precipitation is stacking up to an average California wet season. We'll compare this year's rain and snow to recent drought years and to 1997 and 1998, California's last major El Niño winter.

Video by Katie Schoolov

This year's El Niño is predicted to be one of the strongest on record. We'll be using the KPBS Drought Tracker over the next few months to track the state's rain and snowfall.

San Diego could get buckets of rain, experts say. But if more critical parts of California stay dry, the KPBS Drought Tracker will provide a statewide reality check.

"San Diego people should understand that we import over 80 percent of our water," said David Pierce, another climate researcher at Scripps. "So what actually happens locally in the county doesn't make that much of a difference to our water supply."

Pierce is helping KPBS track statewide rainfall by compiling data from 96 weather stations throughout California. All that data comes together as a percentage of what's normal for a typical California wet season. The numbers will start low and gradually increase as the state accumulates more rain and snow.

"It's continually growing over the whole season," Pierce said. "So today, as we're speaking, it's about 7.5 percent. It goes up every day if we get a little bit of rain."

If the Drought Tracker shows rainfall at 100 percent on April 1, at the very end of the wet season, that means California will have experienced a perfectly normal rain year.

"That's just kind of average," Pierce explained. "Hopefully it will be a typical strong El Niño, and it'll be up there at 150 or 200 percent even."

California also needs above-average snowfall. Though San Diego imports more of its water from the Colorado River, the Sierra Nevada snowpack is a crucial source of water for much of the state. That's why Scripps climate researcher Sam Iacobellis is helping KPBS keep track of snowfall.

"We've come together with a group of stations that represents the different Sierra regions: north, central and southern Sierras," Iacobellis said.

Each year on April 1, California sizes up the Sierra snowpack. A healthy snowpack rises to 100 percent of normal or more, while a low snowpack falls somewhere below 100 percent. The state crafts drought predictions and water conservation goals based on those numbers.

Last year's snowpack was the lowest on record at just 5 percent. Iacobellis said Californians should hope that El Niño steers storms into the mountains, where they'll have a real effect on the drought.

"If it all fell as rain, well, that would help," Iacobellis said. "But it'd be a lot better if a lot of that fell as snow."

Of course, Californians should be careful what they wish for. High levels of rain and snow could help alleviate the drought, but storms could also lead to flooding, property damage and safety hazards for the homeless.

Cayan hopes El Niño will drive storms toward California in manageable bursts, delivering at least 100 percent of normal rain and snowfall throughout the state this winter.

"Anything above that would be icing on the cake," he said. "In order to make a large dent in the drought, I would hope for 150 percent of average."

Come April, we'll consult the KPBS Drought Tracker to see whether or not California made that goal.

KPBS graphics designer Susana Tsutsumi created the interactive California Drought Tracker.

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