The recent rain storms in Reno and snow and rain in the central Sierra Nevada including Lake Tahoe have raised the Lake’s water surface elevation from 6226.23 to 6226.73 – an additional increase of 5 inches in just 7 days. A significant portion of that rise likely came from rain and snow falling directly on the surface of the Lake. Lake Tahoe occupies 40% of its own watershed. The 5 inch rise is equivalent of 50,933 acre-feet or 16.6 billion gallons of water.The rise is dramatic especially when coupled with the more than 3.5 foot of rise between October 2016 to just before the storms of the past week. Lake Tahoe now stands just 2.37 feet below its maximum water surface elevation of 6229.1 feet (set by court decree). With a current snowpack of more than 200 percent of average, Tahoe seems likely to approach or reach its maximum surface elevation.
Tiny flows from Tahoe into the Truckee River
The dramatic rise in Tahoe’s water surface elevation hasn’t resulted in significant flows to the Truckee River from Lake Tahoe, however. In fact, very little water is being released into the Truckee River with flows near Tahoe City, California staying close to 50 cubic-feet-per-second (CFS). Compare this to yesterday’s flow in the Truckee River at Reno of 4,500 CFS. Water in the Truckee River is coming from direct runoff from rain and melting snow into tributary streams entering the Truckee River below Lake Tahoe. Lake Tahoe has a dam (built by the US Bureau of Reclamation over 100 years ago) at Tahoe City that controls the release of water into the Truckee River. Under natural conditions flows from Lake Tahoe would be much higher. It is easy to forget that dams control the amount of flow along the river’s entire course. The biggest diversion on the Truckee River is at Derby Dam between Sparks and Wadsworth. (Want to know more about tributaries to the Truckee? Click here.)
Pyramid Lake rising finally
Pyramid Lake rose at least 1.27 feet although unofficial reports say the actual rise to date is higher. The last official measurement of the water surface elevation of Pyramid Lake shows the first rise in elevation since 2011. The next measurement of Pyramid Lake’s elevation should be on March 1, 2017 (no measurement occurred in January, e.g.). Yesterday, flows of the Truckee River at Pyramid Lake were just under 7,000 CFS. By this morning’s report on the Truckee River Operating Agreement website the Truckee River flow at Pyramid Lake’s Nixon Gauge was 6,450 CFS.
Drought areas shrinking
In northwest Reno near the University, I recorded approximately 3.75″ of precipitation in the form of mostly rain with slush and snow at the end of the storm. This is a pretty significant amount of rain/snow for just a little over 2 days and may be a record for us at our house. The NOAA California River Forecast Center website reports that since the beginning of the water year on October 1, 2016, Reno has officially received 9.36″ of precipitation – 126 percent of average for an entire year. The Reno precipitation gauge is located at the airport in southeast Truckee Meadows. Precipitation amounts vary widely across the Truckee Meadows.
The Drought Monitor map released on February 14 may change yet again from that shown below when next released. Drought conditions in Nevada and California have consistently shrunk in size and severity as rain pummeled California and western Nevada and snow piled up in higher elevations of the Sierra Nevada Mountains.