The greatly improved snowpack will improve runoff in the Truckee River and flows to Pyramid Lake this spring. The snow and rain in March did come too little and too late to push us to an average water year, however. How quickly drought conditions on the river will return depends on how rapidly the spring warms up and whether we get additional storms – never to be counted on – during the early spring. Precipitation since October 1 (the beginning of the water year) remains below normal, too, but better than the snowpack. Snow water in the end-of-season snowpack appears to be diminishing year after year, especially the lower elevation snowpack.
The Tahoe and Truckee River basin snowpack water content remains significantly better today than in February. Although the official water content gets counted on April 1, the numbers won’t change too much. So for March 29, the median water equivalent in the snowpack stands at 78% in the Lake Tahoe basin and 83% in the Truckee River basin. However, total precipitation (rain and snow water equivalent) for this water year is better at 97% and 91% of normal. The Carson River basin has more water in the snowpack at 88% which matches the total precipitation percentage – 88%. Overall, the Carson River’s watershed is higher elevation than the Truckee River’s which may account for the precipitation tracking overall precipitation.
Lake Tahoe stands at 6228.6 feet – just 6″ below its maximum legal elevation and 5.6 feet above its outlet rim. The Lake Tahoe dam controls flows out of Lake Tahoe into the Truckee River. The Lake will soon see an increase in runoff from the melting snowpack. How fast it rises will be based on flows into the Truckee River by the Federal Water Master’s office – the administrator of the Federal Court decree that governs water in the Truckee River for both California and Nevada – as well as the temperatures this spring that determine how quickly the snowpack melts. In an average water year, Lake Tahoe sees a rise in elevation of about 3 feet over spring and early summer. Truckee River flows are running above the long-term average now at more than 2,000 cubic-feet-per-second (CFS) at Pyramid Lake.
Pyramid Lake may see a moderate rise if flows in the Truckee River remain high for most of the spring and diversions to the Newlands Project are small. As of February 28, 2018 Pyramid’s elevation was 3,802.37 feet elevation. Pyramid Lake’s historic elevation before the Newlands Project was built was 3,880 feet in elevation. Last year saw a significant rise in the Lake’s elevation – some 10 feet. With a less than stellar water year for 2017-18, however, Pyramid Lake’s elevation will most likely decline again. The highest elevation for Pyramid Lake in the last 25 years occurred in 1999 when it reached an elevation of 3,817 feet.
Water flows from Lake Tahoe into the Truckee River increased dramatically in the past 7 days. How long these flows from Tahoe last will be based, in part, on how rapidly the snow pack melts.