Looking back at 2008: All about the water
October 20, 2008
Sept. 30 marked the official end of the 2008 water year, and unfortunately, it was another disappointing winter as far as precipitation and water runoff are concerned. At the Central Sierra Snow Laboratory at Soda Springs (near Donner Pass), lead hydrologist Randall Osterhuber measured 346 inches of snow and about 45 inches of precipitation. Average snowfall at the lab is 409 inches annually with nearly 54 inches of precipitation. (Precipitation is rain and snowmelt combined.) After 138 years of record, last winter was the 84th driest.
In the Sierra the water year runs from Oct. 1 to Sept. 30 because the beginning of October represents the historic low point for water flow and reservoir storage in the mountains. From early October on, the chances for measurable precipitation increase daily, with the likelihood of rain and snow at its peak from late December through February.
Many of us remember the barrage of snow that hammered the Truckee-Tahoe region for five weeks beginning in early January 2008. The National Weather Service in Reno called it the “Storm of the Century,” and although that may have been a bit of a stretch, heavy snow along with low temperatures generated some of the best powder skiing and snowboarding in years.
For a period of time, hydrologists were exuberant about water runoff forecasts that were significantly above average. Unfortunately, the storm track shifted after the first week of February and the intense, snow-producing weather pattern was gone for good.
It was an interesting winter in that two separate storm periods over the course of five weeks produced the bulk of the season’s precipitation. The heavy and persistent snowfall during Jan-uary and into early February made national news and helped boost our winter economy by ramping up the motivation of winter sports enthusiasts to visit local resorts.
In addition to ensuring great skiing and snowboarding conditions, the big snowstorms also allayed fears of another dry winter like we
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experienced during the 2007 water year, which turned out to be one of the driest on record.
Tahoe ski resorts enjoyed one more significant storm, a healthy 5-foot dump of snow during the third week of February, but for the rest of the ski season Squaw Valley received only a meager 35 inches of additional snow on the upper mountain at 8,200 feet in elevation. A bone-dry March was followed by a parched April and May, which led to the driest spring season on record for the Northern Sierra.
For the first time, hydrologists reported Lake Tahoe’s water level was actually falling during the spring melt due to a lack of runoff, desiccated soils and evaporation.
The lack of late winter precipitation diminished the snowpack and reduced runoff forecasts. On April 1 the statewide snowpack looked good with near average water content, but by May 1 a significant portion of the snowpack had evaporated and the water content had plummeted to just 67 percent of average. The Central Sierra snowpack was even less at 61 percent of normal water content for the date.
Currently, Lake Tahoe’s water level is falling to near its natural rim at which point no water will flow into the Truckee River. With low water levels in Tahoe, the 2008-2009 winter will be crucial to replenishing our regional watersheds, lakes and rivers. The past few years have been characterized by ENSO (El Nino Southern Oscillations) where sea surface water temperatures in the equatorial Pacific have been warmer (El Nino) and cooler (La Nina) than normal, both of which historically tend to affect weather patterns and jet stream activity across North America.
The forecast for this winter is for ENSO neutral conditions, which means that neither El Nino nor La Nina conditions are expected. The lack of a significant ENSO event has led forecasters to predict this winter has equal chances of being normal in both temperature and precipitation on the Pacific Coast. We’ll just have to wait and see how this winter pans out, but since we receive close to 35 feet of snow in a “normal winter” along the Sierra Crest, an average winter will be just fine.
” Mark McLaughlin’s column, “Weather Window,” appears every other week in the Sierra Sun. He is a nationally published writer and photographer whose award-winning books are available at local stores. Mark can be reached at firstname.lastname@example.org.