Environment
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The U.S. Drought Monitor, which publishes its colorful drought map every Thursday, this week is expected to show a slight decline in the dark brown parts of California suffering the most acutely from a drought that has parched the state four years in a row.
It’s raining in California again this week, but 80 percent of the state is in an extreme drought, with over half in an exceptional drought. So it should come as no surprise that a series of recent storms dousing the state are a long way from ending a particularly long overall dry streak that recent research estimates is the most severe in 1,200 years.
But any drop of rain provides some relief — along with the threat of mudslides and flash floods.
State reservoir levels are inching up. The Lake Oroville reservoir reached its low mark on Nov. 21, when it contained only about 898,000 acre feet of water, or about 292 billion gallons. After a storm last Wednesday, that increased 27 percent.
“Still, now it only puts us at 53 percent of the historical average,” said Doug Carlson, an information officer at the state Department of Water Resources. “Our state climatologist has been saying for some time that to consider we have broken the drought, we would have to exceed normal precipitation by 150 percent at the end of the water year,” which runs from October to September.
The average rain and snowfall in a water year dumps about 50 inches of water. California would thus need 75 inches to bust the drought. “One or two rain events in December going into the fourth year of drought is not going to eliminate the problem,” said Brian Fuchs, a climatologist with the National Drought Mitigation Center at the University of Nebraska.
Brian Fuchs
climatologist, National Drought Mitigation Center
So despite above-normal precipitation this month, it’s not enough to make up for the below-normal levels in October and November. Almost 19 inches of rain fell on the state this month. That’s 139 percent of normal, which is less than 14 inches.
“We really need these consistent rain events and snow events for the rest of the winter,” Fuchs said. “December, January and February count for 50 percent of annual precipitation in California … But the region has missed out a year’s worth. You need normal plus the deficit.”
Northern California benefited the most from recent storms that dumped from 3 inches in the northern valleys to 13 inches of rain on coastal mountain ranges north of San Francisco.
“The only area of California that hasn’t exceeded normal precipitation for the month of December is the northwest corner,” said Scott Carpenter, a meteorologist for the Western region office of the National Weather Service in Salt Lake City. “The whole core of Northern California is 5 to 8 inches above normal … But even if we look at the central southern Sierras, they are still below normal.”
Another round of storms that could dump another 2 to 3 inches in the north and up to an inch in the south is hitting the state through Wednesday evening. But there is no sign the storms will ease strict water restrictions and stiff fines for water waste in communities across the state.
“What happens when the landscape becomes so dried out is that there is little moisture in the soil,” Carlson said. “It starts getting compacted and forms a crusted layer on the top part of the soil … It’s almost like concrete.” The water then almost always runs off to streams and rivers — good to replenish reservoirs but not to raise groundwater levels.
He likens December rains to a financially strapped family’s winning a small jackpot in Las Vegas.
“They can’t say, ‘Hurray, our troubles are over.’ They’re still living in a deficit,” Carlson said.
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