More snow and rain could be on the way after Dec 10 according to the US Weather Service. Could this be the beginning of a winter that can make a real dent in the drought? We hope so. The forecast is for warm conditions ahead of the storm. Monday through Wednesday are forecast to have highs close to 60ºF, but cooling into the 40ºs as the storm approaches on Thursday.
(See the National Weather Service 7 Day forecast map on their Facebook page here.)
Right now, Lake Tahoe is nearly 18″ below its rim, although the Lake did get a very slight bump from the storm on December 3 and there was more precipitation in the mountains, too. Recently, the Lake has moved slightly higher, but Pyramid Lake is continuing to drop especially since water diversions to the Lahontan Reservoir are diverting more than half the flow of the Truckee River at Derby Dam. Upstream reservoirs on the Truckee River hold just a fraction of their capacity. So, there is a large deficit that needs to be overcome to produce drought busting river runoff this spring. Whether this storm is the beginning of that hoped for big snowpack and runoff, we’ll not know until the final surveys are done in the spring.
The chart below shows where we stand as of this weekend with water storage. One of the significant facts is that Lake Tahoe is a negative 25 percent. Since it is below its rim, it must receive 180,000 acre-feet of water just to be at its rim so that water can once again begin to flow from Lake Tahoe into the Truckee River at “Fanny Bridge”. The next largest reservoir, Stampede, is at 12 percent followed by Boca at 15 percent. We will revisit this chart again to see how things are changing as the winter progresses.
Here is the latest graphic of Lake Tahoe’s elevation change during the past week. Note that the bumps in elevation and the flattening afterward in a short period of time are generally caused by the increase in elevation caused by winds blowing on the surface of the Lake and pushing the elevation of the Lake higher at the measuring station.