Can We Be Flooded and Still in a Drought?One month ago, California’s Sonoma County came closer than ever to a water crisis: the level of its primary reservoir sunk to an all-time low after three taxing years of severe drought.
This week, as a parade of atmospheric rivers bringing torrents of rain pummels much of the state, the county in the heart of wine country is grappling with the opposite problem: too much water, way too fast.
But even in a time of abundance, when Lake Sonoma is slowly refilling and the Russian River could soon spill its banks, water managers and scientists are not ready to declare an end to the drought.
“We had such a big hole to dig out of to begin this,” said Grant Davis, Sonoma Water’s general manager, as rain soaked Santa Rosa, the county seat. “We are as water managers dealing with something we call weather whiplash — that means extremes on the dry end and extremes on the wet end.”
Scientists say the apparent paradox of dangerous flooding amid historic drought shows how climate change has amplified California’s intense climate — making the dry spells drier and the wet periods wetter, without either season fully counteracting the other’s effects.
Even though California has improved its water management system in recent years, it wasn’t built to cope with such intense storms, experts say. Even if every drop can be captured and stored in a reservoir, it will take a lot more rainfall to erase the state’s years-long water deficit. And rain is just one part of the equation.
“We are in a flood emergency while we still have an active drought emergency,” Karla Nemeth, the director of California’s Department of Water Resources, said in an interview. “That pretty much says it all about the new normal we have with climate change.”
Human greenhouse gas emissions, mostly from burning fossil fuels, have increased California’s average air temperatures by about 2.5 degrees Fahrenheit, according to the state Environmental Protection Agency. These warmer conditions increase water evaporation from vegetation and soil and deplete the mountain snowpack the state relies on for 30 percent of its water storage.
According to the U.S. Drought Monitor, there hasn’t been a week when some part of California wasn’t abnormally dry or worse since 2011. Last year was exceptionally bad: Wells were parched, and cities became dependent on bottled water as the state saw its second-driest year on record.
“We’re starting off from a position of a really severe deficit,” said Noah Diffenbaugh, a climate scientist at Stanford’s Doerr School of Sustainability. “If you don’t get paid for several months, and then your employer gives you one normal monthly paycheck, most people are not going to feel their bank account is back to normal.”
When rain does fall, climate change has made it much more intense and destructive, studies show — and in turn, harder for water systems to absorb. The atmosphere holds 7 percent more moisture for every degree Celsius increase in temperature, which means any given storm will be much wetter in a warmer world.
If forecasts for the next two weeks hold up, 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 over.
“We’re now in a climate where we’re much more likely to have severe water deficits punctuated by wet conditions,” Diffenbaugh said.
Rising temperatures mean more of that precipitation falls as rain instead of snow. Rather than accumulating on mountain peaks, where it will gradually melt into waterways and ecosystems, the water is immediately flushed into rivers and streams. This can overwhelm water systems that weren’t designed to handle such sporadic, severe rainfall, Diffenbaugh said. In a 2019 study in the journal Water Resources Research, he and his colleagues found that flood risk becomes exponentially worse as precipitation shifts from snow to rain.
In California this week, the downpours have soaked soils and caused drought-stressed trees to collapse. Officials fear that landscapes recently scorched by fire may melt into soggy debris flows. Water managers who were once worried about critically low reservoirs are now contemplating releases to stave off dangerous floods.
California is being inundated with rain. Will it ease the drought?
