There is no such thing as a normal winter
At first glance, it looks like the chart for someone with a particularly powerful pulse. Strong and steady, with what seems like uniform ascents and declines. But it's not the beating of a human heart it shows, but the rhythm of the water cycle of Lake Tahoe.
The chart, Lake Tahoe Month End Elevations, 1900-2013, can be viewed from the walkway on the back of the Truckee River Dam. It shows that Tahoe's level drops from mid-summer until the beginning of winter every year, and then slowly rises again the following spring. But there are also more dramatic increases and decreases in the lake level over the years based on the wide fluctuation in the amount of precipitation that falls in the Tahoe region.
While TV meteorologists, in an effort to excite their viewers, commonly pronounce that the current level of precipitation is above or below normal, we need to remember that they are using normal differently then we do. They mean "average," which is just the middle ground between the winters when all we are doing is shoveling snow, and those years when we are praying for snow. There is really no such thing as a normal winter. And even two winters with the same amount of annual precipitation, can be very different indeed. For example, each of the last two winters gave us a similar amount of snow. But during the winter of 2011-2012 when the snows didn't arrive until the middle of January, we were hiking to mountain lakes to ice skate over Christmas. Then last year, a good dose of snow arrived just in the nick of time for Christmas, but then it petered out to almost nothing during the first few months of 2013.
We can also learn from the chart how establishing a legal limit of 6229 feet in 1935 had a powerful impact on the future development of Tahoe. In the early 20th Century, before the legal limit was set, the lake level exceeded 6229 feet six times, including 1908 when it topped out at over 2 feet above the current limit. If Tahoe reached 6231 feet today it would put most of our beaches and many of the piers under water (and some of the lakefront homes as well). Now, while the lake level cannot exceed 6229 feet, it's mother nature that decides how far below it can go. In the last
40 years the lake has dropped below the natural rim several times including 1977-1978 and during an extended period between 1990 and 1994.
What does the future hold? The current lake level has been dropping fast, currently sitting at just about a foot above the natural rim. If recent lake level rhythms continue, however, it's time for the water levels to begin to rise. But since we still haven't figured out how to accurately predict the weather more than a few days away, when that might happen is anyone's guess.