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California is flooded with rain. Will it ease the drought?

California is flooded with rain. Will it ease the drought?

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One month ago, California’s Sonoma County was closer than ever to a water crisis: its main reservoir level had dropped to its lowest level after three years of severe drought.

This week, as a parade of atmospheric rivers bearing downpours pound much of the state, the county in the heart of wine country is grappling with the opposite problem: too much water, too fast.

But even in times of plenty, when Lake Sonoma is slowly filling up and the Russian River may soon burst its banks, water managers and scientists aren’t ready to declare an end to the drought.

“We had to dig such a big hole to start this,” said Grant Davis, general manager of Sonoma Water, as rain drenched Santa Rosa, the county seat. “We as water managers deal with something we call weather whiplash – that means extremes in the dry end and extremes in the wet end.”

Californians prepared for another massive winter storm on Jan. 4 by laying down sandbags and staying indoors. (Video: Julie Yoon/The Washington Post)

Scientists say the apparent paradox of dangerous flooding amid a historic drought shows how climate change has intensified California’s intense climate — making dry periods drier and wet periods wetter, with neither season fully counteracting the effects of the other.

Although California has improved its water management system in recent years, it is not designed to handle storms this strong, experts say. Even if every drop could be captured and stored in a reservoir, much more rainfall would be needed to erase the state’s long-standing water deficit. And rain is only one part of the equation.

“We’re in a flood emergency while we still have an active drought emergency,” Carla Nemeth, director of the California Department of Water Resources, said in an interview. “That pretty much says it all about the new normal we have with climate change.”

Human emissions of greenhouse gases, mostly from burning fossil fuels, have raised average air temperatures in California by about 2.5 degrees Fahrenheit, according to the state agency for environmental protection. These warmer conditions increase water evaporation from vegetation and soil and deplete the mountain snowpack, which the state relies on for 30 percent of its water supplies.

According to US Drought Monitorthere hasn’t been a week where some part of California hasn’t been unusually dry or worse since 2011. Last year was exceptionally bad: Wells dried up and towns became dependent on bottled water as the state saw its second driest year on record.

“We’re starting from a position of really serious deficit,” said Noah Diefenbaugh, a climate scientist at Stanford’s Doerr School of Sustainable Development. “If you don’t get paid for a few months and then your employer gives you a normal monthly paycheck, most people won’t feel like their bank account is normalizing.”

When it rains, climate change has occurred much more intense and destructive, studies show — and in turn more difficult for water systems to absorb. The atmosphere holds 7 percent more moisture for every degree Celsius rise in temperature, meaning a given storm would be much wetter in a warmer world.

If the forecasts for the next two weeks hold, 22 trillion gallons of water could fall on California in the next 15 days, according to meteorologist Michael Snyder’s calculations. That’s enough to fill Lake Mead more than twice.

“We are now in a climate where we are much more likely to have severe water deficits punctuated by wet conditions,” Diefenbaugh said.

Rising temperatures mean more than that precipitation falls as rain instead of snow. Instead of accumulating on mountaintops, where it would gradually melt into waterways and ecosystems, the water immediately flows into rivers and streams. That could overwhelm water systems that aren’t designed to handle such sporadic, heavy rainfall, Diefenbaugh said. IN A 2019 study in the journal Water Resources Researchhe and his colleagues found that the risk of flooding becomes exponentially worse as precipitation shifts from snow to rain.

In California this week, torrential rains soaked soils and caused drought-stricken trees to collapse. Officials fear that landscapes recently scorched by fire could melt into wet streams of debris. Water managers who once worried about critically low reservoirs are now considering releases to prevent dangerous floods.

While dangerous, the recent spate of storms has helped ease the state’s longstanding water shortage.

The Sierra Nevada snowpack is nearly 180 percent of its normal volume for this point in the season — a 10-year high. Scientists hope that California’s weather won’t warm up too quickly in the coming months. This will allow the snow to slowly melt and flow to communities during the summer.

As of January 3, the US Drought Monitor classified entire condition as “abnormally dry”. There are more than 200 reservoirs in California 33 percent below their historical average levels. Monitoring wells show that the state’s groundwater aquifers, which account for more than half of the state’s water supply during drought years, contain only two-thirds of their normal water intake.

Now some parts of the state see as much as inches of rain per hour. But instead of slowly percolating through ecosystems and soils, the rain rushes onto the saturated earth in a destructive deluge. Instead of restoring the depleted groundwater, the flood exceeded the limited capacity of rivers and reservoirs, causing overflows.

This forces water managers in flood-prone areas to strike a delicate balance. Water is the country’s most valuable resource, and managers must hold on to as much of it as possible. But repeated strong storms mean they also need to keep room for flooding.

Those facing the worst drought conditions have other problems. In early December, the Lake Sonoma bill was painfully low, Davis said. The reservoir was below 40 percent of capacity, with a volume of just under 100,000 acre feet. As of this week, it was over 120,000, a good sign, but only about half of what the lake can safely hold.

Faced with unprecedented challenges, Davis said he is nonetheless optimists and that the country is “better prepared than ever” to deal with extreme climate conditions. One source of his hope is pilot program which uses improved forecasting and modeling to make decisions to retain or release water from reservoirs.

Sonoma has used the system, known as Predictive Informed Reservoir Operations, in one of its smaller reservoirs, and Davis credits it with saving thousands of acre-feet of water.

“This is going to be how water managers deal with these extreme events,” he said.

Meanwhile, a wet December and early January is no guarantee that all that water will last until spring. Look no further than last year’s weather, said Ellen Hanak, director of the Water Policy Center at the Public Policy Institute of California. The state saw similar winter storms before an unusually warm and dry stretch wiped out most of the snowpack.

“Last year wasn’t good, even though we started wet,” Hanak said.

California’s traditional rainy season runs from October to April, so a lot will change in the coming months.

“We’ve got a couple of months we still have to play here,” Hanak said. “But this is welcome beginning.’

A key factor in dealing with long-term drought conditions — and ensuring the state’s well-being — will be finding new ways to manage flooding from future megastorms, effectively using one climate disaster to mitigate another.

Hanak and other experts see promise in underground water storage, which is used in some parts of the state but could become increasingly popular as snowfall becomes less reliable.

Jane Dolan, the president of the Central Valley Flood Protection Board, is urging state and local governments to expand floodplains and restore wetlands as a way to protect against heavy storms and recharge aquifers. The recent storms in California show the urgent need to do both, she said.

“We’re paying now to make things more resilient and protect people’s lives and property, or we’re going to pay later by fixing the massive damage that’s occurred,” said Dolan of Chico, the state’s largest city in the north from Sacramento, where she spent decades in local government.

“Water is the number one issue in California,” she said. “We either have too much of it or not enough.




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