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Rain No Help For California Reservoirs

Marnette Federis / Capital Public Radio

Lake Oroville Reservoir in November 2014.

Marnette Federis / Capital Public Radio

A fifth year of drought is likely in California, and El Niño won't end it, say water scientists and forecasters.

Water managers can only wait, hoping the fall and winter precipitation brings enough snowpack and rain to ease four years of drought. The snowpack last year was gone in early spring.

The California Department of Water Resources reported that the statewide snowpack on April 1, 2015, held only 5 percent of the average water content for that date - in records dating to 1950.

The previous low record of 25 percent of average was set in 1977 during one of California’s most significant droughts and was tied in 2014, according to the DWR.

"Of the nine April 1 snowpack readings below 50 percent of average since 1950, three have occurred in the past three years of drought," the DWR reported in late-September.

Unseasonably Heavy Rains No Help For Reservoirs, Drought

The U.S. Drought Monitor released Oct. 8 shows no difference in the percentage of drought in California, as 92 percent of the state is in severe drought, 71 percent is in extreme and 46 percent is in exceptional drought.

In Nevada, 76 percent of the state is in severe drought, 37 percent is in extreme and 15 percent is in exceptional drought.

The Drought Monitor intensity levels are Abnormally Dry, Moderate, Severe, Extreme and Exceptional Drought.

"With September and October normally one of the driest months in California, any significant rain (more than 0.5 inches) that falls during this time will usually produce large percentages. This was the case this week when a strong upper-air trough (low pressure) affected the West Coast, drawing in Pacific moisture to most of California and the Great Basin," according to the weekly report.




"Unseasonably heavy precipitation (0.5 to 1 inch, locally to 2 inches) was observed in extreme southwestern California (near San Diego vicinity), the Sierra Nevada, and most of northern and western Nevada including the Las Vegas area," the drought report noted.

But, while the rains "were welcome and aided in the suppression of wild fire conditions and increased topsoil moisture, it did little for the long-term drought and reservoir storages, thus no changes were made to the drought map."

The report did say that at the end of September, "the water conservation efforts in California were noticeable when compared to last year and so this year’s major reservoir storage was only slightly below the storage from a year ago when there were no mandatory water restrictions."

In the Pacific Northwest, Oregon and Washington are 100 percent in severe drought. Extreme drought covers 67 percent of Oregon and nearly 68 percent of Washington.




Major California Reservoirs 50 Percent Of Average


The U.S. Bureau of Reclamation reported Oct. 6 that six key California reservoirs for its Central Valley Project hold 2.9 million feet of water.  The amount is what is carried over to the new water year which started Oct. 1.

The federal agency says the 2.9 million feet is 47 percent of the 15-year average carryover for the reservoirs. 

"We’re about 200,000 acre-feet lower than we were a year ago," said Shane Hunt, with the U.S. Bureau of Reclamation.   

Hunt says the water year is starting with nearly double the water volume than the driest year, which was 1.5 million acre-feet in 1977.

"But you do see the pace of the decline has slowed over that same period also," says Hunt. "We would hope to not get down to that 1977 level."

One acre-foot is enough water to supply a typical California household of four for one year.


1008 CA Reservoir


El Niño May Help But Won't End California Drought


A strong El Niño is not expected to make a difference in terms of ending the drought in California.

"The deficit right now is somewhere around 12 trillion gallons of water," Jay Famiglietti, Senior Water Scientist with NASA's Jet Propulsion Lab and a Professor of Earth Systems Science at UC Irvine, said in August. "So we need to replace about 12 trillion gallons of water in storage, in snow, in groundwater, in our reservoirs. That’s going to take about three years of above-average precipitation."

"So, one El Niño year will help, if it actually brings rain to California, which is not guaranteed," Famiglietti said. "But we need a few years in a row of above-average precipitation to dig out of this monumental hole that we’re in."

A PBS video explained the nuances of short and long-term weather forecasting:  "El Niño and Why We Can’t Predict the Weather."

Michelle Mead, with the National Weather Service in Sacramento, says the video "basically answers the question of why we're sometimes wrong."

As to El Niño helping this winter, Mead says "due to the confidence of a strong El Niño lasting through the winter, it is looking more favorable that Northern California could see above average precipitation in the latter part of Winter (Dec-March)."

But Mead says, the ocean warming condition won't end the water supply deficit caused by four years of drought.  And, she says colder storms - from the Gulf of Alaska - bring better potential for snow. 


The U.S. Seasonal Drought Outlook shows drought persists and intensifies over much of California and Nevada through December 2015, and over all of Oregon and Washington. But, the outlook shows some improvement to California's central and southern coast. 

The seasonal outlook for precipitation and temperature will be updated October 15. 


0924 Seasonal Outlook


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