SoCal Forecast For 21st Century: More Rain, Less Snow

Los Angeles may be getting more of its drinking water from rain | Photo: Steve Devol/Flickr/Creative Commons License

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It's not certain whether the Los Angeles region will get drier or wetter as a result of human-caused climate change in the next 85 years, but whatever precipitation we we do get will be more rain than snow, according to a study by a team of UCLA meteorologists.

"Will there be rain in L.A.'s future? Unquestionably yes," says Alex Hall, lead author of the paper in the Journal of Climate that came out of the study. "The Los Angeles region resides in between a wetter northern rain regime and a dryer southern one. These two influences have been in a tug-of-war for millennia, and our analysis suggests this pattern will continue."

The paper suggests that any changes in the total amount of precip L.A. gets between now and the end of the century are likely to be within the normal range of extremes measured between 1981 and 2000. But the region will be warmer, and that means that more of the precipitation Los Angeles' mountainous backdrop gets will come as rain rather than snow. And that means trouble.

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"Although we don't expect the total amount of precipitation to change much," says Hall, "we know from the snowfall study that warmer temperatures will cause less of that precipitation to fall as snow. Instead, it will fall as rain, which runs off our mountains much more quickly."

That means more potential problems with landslides and flooding, especially if wildfires increase in the San Gabriel mountains. It also means less winter precipitation will stay conveniently up in the mountains until spring, which means Angelenos won't have as secure a local water supply through the summer months.

But the Los Angeles Department of Water and Power is nonetheless moving ahead with plans to increase the percentage of water it sources locally. "The study, frankly, helps us move forward with our plans," says Martin Adams, LADWP's Senior Assistant General Manager for Water. "The study gives us confidence to proceed with our utility's plans to increase local water supply from 11 percent this year to 36 percent by 2035."

The future of water use in Los Angeles may well lie in learning to capture much more of that rainy runoff, say environmentalists.

"Every inch of rain we fail to capture results in the loss of 3.8 billion gallons of water," said Environment Now executive director Shelley Luce. "The recent rain event on December 2 and 3, if captured, could have supplied over 4 percent of the city's annual water needs. The UCLA study suggests we can indeed rely on local rain for our water needs -- and we must be willing to make the investment."

For ongoing environmental coverage in March 2017 and afterward, please visit our show Earth Focus, or browse Redefine for historic material.
KCET's award-winning environment news project Redefine ran from July 2012 through February 2017.

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