Unusual rainfall pattern for latest water year
July 10, 2013
Prevailing wisdom had this water year (July 1, 2012, to June 30, 2013) pegged as one of the driest — but the statistics tell a different story.
Grass Valley received about 44.65 inches of precipitation during the year-long period, which represents 83 percent of the normal precipitation for the Sierra foothills (53.80 inches), according to the National Weather Service.
The index, which measures rainfall accumulation at eight locations throughout the mountainous region of Northern California, ranging from Mt. Shasta City down to the American River basin, was 91 percent of the average year, said Eric Kurth, meteorologist with the weather service.
However, Kurth said the old adage that statistics don’t lie doesn’t hold water in the present instance.
“It’s been a pretty odd year, to say the least,” Kurth said. “If you just pick one number out and say, ‘It’s been an average year’ — well, that number can be deceptive.”
Kurth said the timing of when the precipitation falls and in what form dictates how usable the water is for Northern California residents.
In the present year, rainfall came early and often (October-December), then stayed away for much of the rest of the year (January-May), while getting a little bump toward the end of June, Kurth said.
However, an early melt means large water agencies will bypass storage due to anticipation that more precipitation will come later in the year.
“A lot of water went down through the valley and out into the ocean, this year,” Kurth said.
Sue Sindt said Nevada Irrigation District is able to avoid having to forgo storage in the early part of the year, as the scale of its operation exempts it from certain mandated flood-storage parameters.
Thus, NID began storing water early in the water season and the agency’s water storage levels hovered at 102 percent of average at the end of June, Sindt said.
Sindt agreed the water year was not true to form for Northern California.
“It’s unusual how wet it was in October and November and how dry December through May was,” she said.
However, Sindt said NID “monitored the weather and the snowpack all season long and responded accordingly.”
Sindt said the late June moisture helped slow the rate of withdrawal from some of the reservoirs, partly due to run-off collection but mostly due to decreased demand from customers.
Sindt said she expects the carryover to next year to be about average for NID.
After the brutal heat wave saw temperatures in the foothills rise above 100 degrees for several consecutive days, average temperatures will return to the region over the next week. Temperatures will hover in the low 90s for the front of the week, and the mercury will delve into the high 80s beginning Thursday and through the weekend, Kurth said.
A low-pressure system has moved into Northern California, bringing cooler temperatures in tow.
The humidity that exacerbated last week’s sustained heat wave has dissipated altogether, Kurth said.
Sunny skies will prevail throughout the week.
To contact Staff Writer Matthew Renda email firstname.lastname@example.org or call 530-477-4239.
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