Dry winter in the Sierra may continue, but water supplies are OK in Truckee Meadows
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It's a week into 2014, and the bare peaks and rocky banks of the Sierra are harbingers of what could be an increasingly dry year. On Friday, the first readings of the snowpack south of Tahoe were described as abysmal by California scientists. Lake Tahoe is only at about 10 percent of its reservoir's capacity.
"We're off to a very slow start for the year. We have, maybe, a third of the average snowpack and the prospects for adding to that are pretty low."
Kelly Redmond is Deputy Director of the Western Regional Climate Center at the Desert Research Institute.
"No more than dribs and drabs this week, and then it looks like the ridge off the West Coast is going to rebuild next week and shunt the storms, such as there might be, into Alaska."
That high pressure ridge continues to push storms away from the Sierra. Redmond says it's the counterpart to the trough on the East Coast, which has been pounded by snow and cold weather. He says it's a relatively stable weather pattern and can persist for several weeks at a time. While it's hard to project out past that timeframe, he says new experimental modeling from NOAA is hinting strongly that dry conditions could persist through spring.
Still, Redmond says we're not even at the halfway point yet for winter precipitation.
"It does takes just only one or two pretty large storms to make a big dent in the deficit."
Previous years play that out. In 2010, the snowpack in the Truckee River Basin, which is the largest watershed that the Truckee Meadows Water Authority (TMWA) uses, was about 80 percent. The next year it nearly doubled. Since then, it has dropped back down to about 50 percent.
John Erwin is a director at TMWA.
"Currently, the river is meeting all the demands of our customers."
Erwin says there may not be that much snow, but there are always some flows in the Truckee during the winter-not necessarily from Tahoe-but from smaller sources like creeks and snow melt. After that, the spring runoff comes, which means there's only a fraction of the year when they'll need to call upon drought supplies.
"You do get precipitation. You may not get significant amounts, but you always get some to support the river generally from October through June. It's just those months-July, August and September-that we've compressed all our drought supplies to be used during that period."
Historically, there's usually no more than three straight years with snowpack as low as 50 percent, except for in the early 90s. While 2012 through 2014 is shaping up to look like that dry period, Erwin says the difference is the utility now has the technology to store and access drought reserves only at the end of summer when it's most needed. They have enough water in reservoirs like Donner Lake, as well as groundwater, to last 9 years of the most severe drought levels.
California is currently taking emergency drought measures because much of the southern portion of the state relies on the Sierra for its water. The Truckee Meadows, Erwin says, is blessed with high altitude reservoirs and plenty of smaller sources to keep the water running into 2014.