El Nino unlikely to quench reservoirs’ thirst in California

As the first of several El Nino-driven storms drenched California on Jan. 5, state authorities and meteorologists caution that even the wettest of winters and higher than normal snowfall cannot completely replenish the state’s depleted reservoirs.

Mammoth Mountain, located in Eastern California along the east side of the Sierra Nevada mountain range in the Inyo National Forest, recorded 5 in of snowfall on Nov. 15 to bring its monthly total to 38 in, almost three times the 13 in it received November 2014.

Diamond Valley Lake is Southern California’s largest reservoir and it features three earth fill dams, two located on either side of the valley and one on the north rim. It draws much of its supply from the far reaches of Northern California. The Metropolitan Water District of Southern California (MWD) began the US$1.9 billion construction project in 1995 and it was completed in 2003.

As much as 15 in of rain and additional snow could fall in the next 16 days in Northern California. About 2 ft of snow is expected in the highest points of the Sierra Nevada, said Johnny Powell, a forecaster with the National Weather Service. But, a report by the Los Angeles Times said, a single year of heavy El Nià±o rains is unlikely to fill up Diamond Valley Lake Reservoir to full capacity, according to Bob Muir, spokesman for MWD.

So many wells and reservoirs farther north are so dry, it’s hard to say how much Southern California would get, he said.

Large capacity reservoirs similar to Oroville and Shasta, and many hundreds of small reservoirs up and down the state, as well as the groundwater basins take a long time to fill and it has never happened in one winter, said Bill Patzert, climatologist for NASA’s Jet Propulsion Laboratory in La Canada Flintridge.

In Southern California, between 2 and 3.5 inches of rain are predicted to fall across the coastal and valley areas, and up to 5 inches falling in the mountains.

Flash flooding and flows of mud and debris were a concern, especially in places left barren by last year’s wildfires.

California’s water deficit is so deep after four years of drought that a “steady parade of storms” like these will be needed for years to come, said Mike Anderson, climatologist for the state’s Department of Water Resources.

The current El Nino — a natural warming of the central Pacific Ocean that interacts with the atmosphere and changes weather worldwide — has tied 1997-98 as the strongest on record, the National Oceanic and Atmospheric Administration’s Climate Prediction Center said, citing statistics that go back to 1950.

El Ninos usually bring heavy rains to California, although it remains to be seen whether people should expect anything like a repeat of 1997 and 1998, when storms killed 17 people, wiped out crops, washed out highways and pushed houses down hillsides.

“DarthNino may finally have California in its sights,” said Jeff Masters, meteorology director of the private Weather Underground.

“A parade of strong Pacific storms characteristic of a strong El Nino event will batter the state this week and will likely bring damaging flooding by the time the second storm in the series rolls through on [Jan. 6],” Masters said.

However, Masters and meteorologist Ryan Maue of the private WeatherBell Analytics do not believe this first storm is as powerful as some other Pacific storm systems, and they caution that the storms now following it may land elsewhere.

The current forecast calls for a “kind of a nice level of bombardment” over the next two weeks — probably not enough to cause the tremendous flooding of 1998, but then again, that year’s floods did not peak until February, Masters said.
 

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Gregory B. Poindexter formerly was an associate editor for HydroWorld.com.

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