Sierra snow survey points to dry year ahead
01/03/2014 12:27 PM
10/08/2014 11:30 AM
One month into winter, and it looks a lot like summer all across California.
The state is experiencing one of the driest starts to winter ever recorded, proved by the clear blue skies and record-warm temperatures that have persisted over the past few weeks.
How dry is it? The depth of the problem was exposed in plain terms on Friday when the California Department of Water Resources conducted its first Sierra Nevada snow survey of the season. Surveyors reported the snowpack is only 20 percent of average as of Friday across the mountain range that serves as a crucial water bank for the state.
In the northern mountains, home to the state’s largest water storage reservoirs, the snowpack is just 10 percent of average.
That ties a record for the driest snow survey ever recorded in January, equaled only by the same month in 2012, DWR reported. That year became the first of two dry winters, and it looks increasingly like a third is underway.
“While we hope conditions improve, we are fully mobilized to streamline water transfers and take every action possible to ease the effects of dry weather,” DWR Director Mark Cowin said in a statement. “And every Californian can help by making water conservation a daily habit.”
Even more concerning to state water providers is the forecast. On New Year’s Eve, the National Weather Service predicted that California is likely to see below-average rainfall for the entire month of January. That means the state is likely to emerge from winter with two of its wettest months essentially missing.
“The water situation is bad. We’re kind of in unprecedented conditions,” said John Woodling, executive director of the Sacramento Regional Water Authority, which represents more than two dozen water providers in the capital area. “We’re looking at a year that’s potentially going to be worse than the 1976-77 drought.”
A number of area water agencies already have ordered mandatory 20 percent reductions in water use for residential and business customers. Others are likely to follow with similar measures in the weeks ahead, including the city of Sacramento.
The local conservation measures are dictated largely by low storage in Folsom Lake, the primary water supply for many area cities. The reservoir stands at 19 percent of capacity and is falling rapidly amid negligible upstream runoff from the American River.
Streams and rivers across the state are depleted. According to gauges maintained by the U.S. Geological Survey, only 25 percent of the 215 monitored streams had “normal” water flow as of Friday, and 71 percent were below normal. About 21 percent are at unprecedented lows, a number that has doubled in the past two weeks.
These stream flows are crucial not only for fish and wildlife, but also for cities and farms that draw water from them.
“The big reservoirs that provide a lot of the state’s water, they’re not going to get a lot of recharge unless things really turn around,” said Alan Haynes, acting hydrologist in charge at the California-Nevada River Forecast Center, a branch of the National Weather Service in Sacramento. “It could happen, but chances are it’s not going to recharge the reservoirs a whole lot, and then we’ll be starting from a low point next summer.”
The lack of precipitation is caused by an enormous and persistent area of high pressure parked over the Gulf of Alaska for months. It has detoured the normal storm track far north of its usual route through California, leaving the state stormless.
“We do have quite a few (storm) systems lined up there out in the Pacific,” said Michelle Mead, warning coordination meteorologist at the National Weather Service in Sacramento. “All those systems have been diverted to the north of us.”
It is unclear why that high-pressure ridge has persisted. It may be a result of a phenomenon called the Pacific Decadal Oscillation, or PDO, which is like a larger and longer-lasting version of the ocean temperature phases that occur during El Niño and La Niña years. As the name implies, this particular cycle can lock in place for years and even decades.
The PDO is currently negative, meaning the northern Pacific Ocean is cooler than average. Bill Patzert, a climatologist at the NASA Jet Propulsion Laboratory in Pasadena, said droughts in California often are associated with a negative PDO. He argues that California is in the midst of a decades-long drought that began in 2000.
“The negative PDO tends to look like this,” Patzert said. “It tends to keep those Pacific storms quiet and certainly out of California. If there’s anything intelligent to forecast, it certainly looks like more of the same.”
The National Weather Service reports that a couple of storms may break through the high pressure and reach California on Tuesday and Thursday. But they are expected to be weak by the time they reach the state, and bring little if any precipitation.
Then the high pressure is projected to strengthen all over again.
Daniel Swain, a doctoral candidate in climatology at Stanford University, has been studying the situation and reporting about it on his blog, weatherwest.com. He said the high pressure ridge has been in place since December 2012. After examining relevant weather records dating to 1948, he believes such a persistent ridge has never been seen before.
“It’s at least unprecedented in the observational record in that particular region,” said Swain, who earned his bachelor’s degree in atmospheric science at UC Davis. “I definitely think it’s a significant event.”
Water agencies across the state are beginning to brace for a third dry year. The situation could be acute for Sacramento-area water agencies that depend on water stored in Folsom Lake. To preserve what remains in the reservoir, the U.S. Bureau of Reclamation on Jan. 1 trimmed releases into the American River to 1,100 cubic feet per second. On Tuesday, it plans to reduce releases to 800 cfs.
“It’s not too early to start conserving,” said Woodling, of the Sacramento Regional Water Authority. “It’s been a dry winter and I think some people need to reduce their outdoor water use right now who have been watering during the winter. People need to step up and get it done and recognize it means more water for later in the summer.”
Water agencies that depend on the Sacramento-San Joaquin Delta, a collection point for Sierra snowmelt, also could see shortages later this year, especially farmers. DWR currently estimates it will be able to provide its 29 water contractors with only 5 percent of the water they requested for 2014. That could change if the winter gets wetter, but that doesn’t seem likely right now. Those contractors serve 25 million people and 1 million acres of farmland between San Jose and San Diego.
“The state’s agricultural areas will see major impacts as the lack of water will result in the need to fallow important farmland,” Terry Erlewine, general manager of the State Water Contractors, said in a statement. “These conditions are worse than some of the most devastating droughts our state has ever seen.”
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