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El Niño Slightly Improved The Drought But Didn’t Bust It
Here’s what we’ve learned from the KPBS Drought Tracker
Monday, April 11, 2016
El Niño Slightly Improved The Drought But Didn't Bust It
Dana Friehauf, water resources manager, San Diego County Water Authority
For the past few months, we've used the KPBS Drought Tracker to tell you how much rain and snow El Niño has been bringing to California. After a fairly average wet season, where does California's drought stand now?
For the past few months, we've used the KPBS Drought Tracker to tell you how much rain and snow El Niño has been bringing to California. Now that we've reached the end of what turned out to be a fairly average wet season, where does California's drought stand now?
We've limited our focus to California’s wettest months, which stretch from October to the beginning of April. We could still see some rain in coming weeks, but California’s traditionally defined wet season is now over.
When we launched the KPBS Drought Tracker, climate experts told us rain and snow levels would have to reach 150 percent of normal by April 1 to really put a dent in the drought. This year's numbers didn't come close, but they were an improvement over all previous years in California's prolonged drought.
Last year, Sierra snowpack hit a record low on April 1, measuring just 6 percent of its normal level. This year's measurement was just below normal at 91 percent. Statewide rainfall was also higher than in previous years, topping out at 108 percent of normal by April 1.
But this year's numbers were nowhere near as high as those seen in 1998, toward the end of the last major El Niño. California received 164 percent of its normal rainfall that year, and 166 percent of its typical snowpack.
So where do today's numbers leave us? Has the drought gotten any better?
To find out, we asked the Scripps Institution of Oceanography climate researchers who helped compile data for the KBPS Drought Tracker.
"In very broad measure, I’d say we’ve gotten a little better,” said Scripps climate researcher Dan Cayan.
But not so much better we can safely go back to pre-drought water consumption.
Cayan said El Niño rains filled some major reservoirs in Northern California. But precipitation was not evenly distributed throughout the state, leaving other areas fairly dry.
"In this case, the West Coast distribution of precipitation — wet in the north, dry in the south — was pretty much topsy-turvy of what we expected,” Cayan said.
The U.S. Drought Monitor shows that about 75 percent of California remains in "severe" drought or worse.
Cayan said continued conservation would be prudent, because we don’t yet know what’s in store for California’s next wet season.
This winter’s strong El Niño pattern is starting to break down, and the National Weather Service’s Climate Prediction Center says there’s a 50 percent chance it could give way to a La Niña pattern by fall.
David Pierce, another Scripps climate researcher who helped with the KPBS Drought Tracker, explained, “An El Niño is when it’s unusually warm in the tropical Pacific Ocean. And a La Niña is when it’s unusually cool at the tropical Pacific surface."
If we are in for a strong La Niña, California could be headed for another year of drought. That's because La Niña "is associated with dry conditions," Pierce said.
He has seen some evidence of a budding La Niña pattern in the Pacific. But he says it’s still too soon to predict whether it will set in.
"Right now, a majority of the models are showing we might go to La Niña conditions. I personally think it’s pretty far out to say that with any certainty," Pierce said.
What we do know about the next few months is that current snow levels won't pull us out of the drought.
The Sierra snowpack, which provides about a third of California’s total water supply, never quite got to 100 percent of normal this wet season.
Cayan said that’s in part because at various points this winter, temperatures were relatively high in California.
“And, of course, that makes for rain instead of snow and tends to melt snowpack a bit earlier,” he said.
This winter wasn't as warm as past winters in the drought. But it was warm enough to affect snowpack growth. Cayan said this could be a preview of how global warming will affect the Sierra snowpack in the future.
He has a model showing that for every degree of Celsius in warming, California will lose about 20 percent of its April 1 snowpack.
“By the end of the century, you can see here, in this particular example, we’ve lost more than half of the snowpack," Cayan said.
Less snowpack will mean less water stored up for spring and summer. He said climate change is going to shift our understanding of normal for this crucial water source.
“It’s going to be a different form of water management that we’re confronted with,” Cayan said.
So, what have we learned from the KPBS Drought Tracker?
We’ve learned that it’s hard to predict how exactly El Niño will impact California. Even strong El Niños don’t necessarily bring record rain and snow to the state.
And we’ve learned that despite big improvements over recent years, the drought is far from over.
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