Weather Window | Winter wrap up dry subject
June 19, 2014
Water year 2014 still has more than three months left on the clock (it ends Sept. 30), but for all intents and purposes California's rainy season is done.
Unfortunately, last winter wasn't very wet. Data provided by Randall Osterhuber at the Central Sierra Snow Laboratory at elevation 6,900 feet near Donner Pass indicate that winter 2014 ranks as the third least snowiest since 1879, with a total 194 inches. That measurement is virtually tied with 1924 at 195 inches, but behind 1881 and 1977 for the all-time most meager annual snowfall.
At the base of Squaw Valley ski resort, less than 98 inches fell during the whole winter. As in most years, snowfall amounts were more generous at the higher elevations. According to the Squaw Valley snowfall tracker, during the 2014 ski season the resort tallied 296 inches of snow at its upper mountain stake located near 8,000 feet, which is more than 1,000 feet higher in elevation than the Snow Lab.
HOW DRY IS DRY?
Last year media headlines claimed that the 2013 calendar year was the driest in California since records began in 1850.
But precipitation is officially measured in water years, not calendar years. Yes, it was exceptionally dry during those 12 months, but hydrologists, meteorologists, and water districts all subscribe to the official Water Year when measuring and comparing seasonal precipitation. In California the lowlands calculate precipitation based on a July 1 to June 30 cycle. In the Sierra, however, the water year runs from Oct. 1 to Sept. 30. (Precipitation is the combination of rain plus snow melted for its water equivalent.)
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At Donner Pass, water year 2014 wasn't even close to being the driest. The 35.7 inches of precipitation measured at the Snow Lab last winter ranks 25th on the dry list since 1871. For purposes of comparison, that total of nearly three feet of water makes 2014 much wetter than 1924, the all-time driest with only 18.9 inches of precipitation. In case you're wondering, the wettest year of record at Donner Pass is 1982 with 112 inches.
Similar to last year, severe drought conditions continue to plague much of California and Nevada. Based on the Northern Sierra 8-Station Index, 2014 precipitation currently stands at 28.8 inches, compared to the annual average of 50 inches, making 2014 the third consecutive year with below normal snowfall and precipitation throughout the Northern Sierra. Last winter was bad, but 2013 wasn't much better as it ranked fifth least snowiest at the Snow Lab.
Despite the lack of precipitation over the past few years, Lake Tahoe's water level is currently more than a foot above the lake's natural rim. That's pretty good considering that during an extreme drought from 1987 to 1992, the water level in Tahoe fell three feet below the rim, four feet lower than it is today. That extended dry spell cut off Tahoe's flow into the Truckee River for more than two years.
IN THE TRENCHES
During another drought in the late 1920s and early 1930s, the Truckee River dried up and failed to provide water for western Nevada agriculture. As frustration grew, a group of Truckee Meadows farmers threatened to dynamite the rim of the lake to allow water out. The threats jump-started a series of negotiations among Tahoe lakeshore property owners, business groups, and both state and federal governments, but no solutions to the ongoing water war were forthcoming.
At one point, men from Nevada attempted to dig a trench past the Tahoe Dam in order to drain off the lake. A steam shovel escorted by a Reno police force was deployed to land adjacent to the dam and a diversion ditch begun. Tahoe sheriff's representatives formed a posse to prevent the ditch digging until a judge ordered an injunction to halt the operation. The steam shovel was shut down and the trench backfilled.
Extremely dry conditions in the mid-1970s nearly dried up Northern California's reservoir system and crippled the Golden State. Indicative of the parched conditions, only 183 inches of snow fell at the Snow Lab in 1977, the second lowest amount on record. The positive aspect of that drought is that it was relatively short-lived and it led to permanent water conservation in California, particularly in the Bay Area where cities realized they could implement comprehensive policies to reduce urban consumption by 40 percent.
Wetter conditions in winter 2015 will be critical for Tahoe-Sierra ecosystems and reservoirs to recover somewhat from the current dry spell.
Forecasters are relatively confident that a developing El Niño event in the Pacific Ocean will play a role in next winter's weather, but no one can say at this time how strong the episode will be or whether it will bring the much needed rain and snow that the region so desperately needs.
Weather historian Mark McLaughlin is a nationally published author and professional speaker. His award-winning books are available at local stores or at http://www.thestormking.com. You can reach him at firstname.lastname@example.org. Check out Mark's blog: http://www.tahoenuggets.com.
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