To nudge California out of drought territory, it will take almost double the amount of rain that falls in a normal year during the upcoming rainy season that starts in less than two weeks, according to a recent analysis prepared by National Oceanic and Atmospheric Administration meteorologists.
As flood-control channels surge, records would shatter. Southern California and the San Joaquin Valley — the state’s agricultural heartland — would need between 160 percent and 198 percent of normal rainfall, wrote NOAA meteorologist Tom Di Liberto, in a Sept. 11 paper titled “How Deep of a Precipitation Hole Is California In.”
That kind of record rainfall — something that has occurred three times in the past 135 years — only would lift the state from the bottom 20 percent of precipitation totals, the lowest possible rainfall cumulation that no longer qualifies as drought by the NOAA Climate Prediction Center. In academic terms, California would score a passing grade — barely.
If the state were to reach 50 percent for five-year (2011-2016) rainfall totals, Di Liberto calculates the coast of Southern California would have to experience rainfall at 300 percent of normal, or about 53 inches in one year, about 15 inches above the wettest year on record for Los Angeles.
“This deficit isn’t so much a hole as a giant chasm,” he wrote.
WILL EL NIÑO SHOW UP?
“Thirty inches of rain would be remarkable for Southern California. Double that? That might take five to six years,” said Bill Patzert, climatologist from the Jet Propulsion Laboratory in La Cañada Flintridge.
NOAA meteorologists are predicting there is a 95 percent chance an El Niño will occur, one strong enough to bring above-average rainfall to California.
“This El Niño ranks among the strongest in the historical record for this time of year, and forecast models predict it to last into 2016,” according to an assessment from the NOAA Drought Task Force of possible El Niño winter impacts in California.
NOAA forecasters couch that prediction, saying some El Niños can do the opposite and spread dry conditions. But most climatologist predictions lean toward a very strong El Niño happening, such as the two that dumped record rains and caused devastating floods to Southern California in the winters of 1982-1983 and 1997-1998.
Shifts in climate patterns are already evident, Patzert said. Drought conditions are occurring in Southeast Asia. The subtropical jet stream is moving north, situated perfectly to corral Pacific storms.The recent storm that left 2.4 inches made for the second-wettest September day in downtown L.A. Patzert characterized it as an opening act with the main event penciled in for late winter.
NOAA models say the building El Niño “could greatly dent the drought” in California. The strongest possibility for rain would be in February, March and April, according to NOAA predictions.
LESS IMPACT IN NORCAL
When is not as important as where. Again, the NOAA analysis says it’s more likely heavy rains would hit Southern California than Northern California. NOAA forecasters give Northern California a 50 percent chance for precipitation above 140 percent of normal.
That would not help refill state reservoirs currently at 54 percent, because much of Southern California imports 60 to 70 percent of water from the State Water Project that draws from reservoirs that are fed by snowmelt in the northern and southern Sierras.
WHY 1 YEAR ISN’T ENOUGH
The effects of the driest four years in California history will be hard to reverse.
“We are about 40 inches below where we should be,” said Ted Johnson, a hydrogeologist with the Water Replenishment District of Southern California. The district serves 43 cities in a 420-square-mile service area from Los Angeles to Long Beach in the south and from Cerritos to Redondo Beach in the west.
In the past four years, Southern California got 32 inches of rainfall, when it should have received 70 inches, he said. The region needs 38 to 40 inches of rain to bust the drought, he said.
“It is obviously going to take two to three years of above-normal rainfall to get out of the drought. One year will not do it, even if this El Niño gives us 35 inches of rain,” he said.
With 99 percent of the San Gabriel River water being captured, local rains will help replenish Southern California’s unheralded but hardworking resource: groundwater basins.
HARD WORK AHEAD
Johnson monitors the Central Basin and the West Coast Basin, which are both at the lowest levels in 55 years. Stormwater is funneled to various spreading grounds — open swaths of land with porous soil — where water percolates into the aquifers. WRD’s San Gabriel Coastal Spreading Grounds suck in stormwater, recycled water and imported water when available.
To the north, the vast San Gabriel Basin has dropped 75 feet in 10 years, reaching an all-time low this summer.
Water is pumped from wells to serve millions of Southern Californians, but these aquifers need artificial replenishing. Usually, the state delivers replacement water from Northern California and the Colorado River but that source has been cut off, Johnson said.
The San Gabriel Valley Municipal Water District pumps water from Northern California into Lake Silverwood into the San Gabriel Basin. But according to its 2014-2015 annual report, recharging the basin with imported water has fallen off dramatically, from 23,040 acre-feet in 2011 to 1,200 acre-feet in 2014 — a drop of 95 percent.
While groundwater basins in Los Angeles and San Bernardino counties are low, they are not sinking, as are some in the farming areas of the San Joaquin Valley. There, farmers are pumping 24 hours a day. New wells are being dug at record rates, Johnson said.
“Any rain helps,” Johnson said. “The more the better.”