Last week, Lee Vining Creek peaked on Thursday night, June 23, at approximately 536 cubic feet per second (cfs), according to preliminary data from the Los Angeles Department of Water & Power (DWP). Southern California Edison is releasing additional water from Saddlebag Lake Reservoir and almost the entire natural flow from Tioga Lake Reservoir, which resulted in a very high peak flow on Lee Vining Creek. This peak flow was about the same as last year’s average daily peak flow, which had only been exceeded twice since 1980 (in 1995 and 1997). The timing of these reservoir operations when the snow melts late and suddenly (this year and last year) just happen to match Synthesis Report recommendations for increasing Lee Vining Creek’s peak flow in order to promote restoration of the creek.
Very warm air temperatures for three nights in a row preceded the peak. Thursday morning low temperatures above 9,000 feet were as warm as 48 degrees, allowing rapid melting of the high elevation snowpack to continue all night and peak under the post-summer-solstice sun the following day. The nearby Dana Meadows snow pillow recorded a loss of 2.3 inches of water from the snowpack that day, and the 10,750-foot Gem Pass snow pillow recorded a 1.76-inch drop in water content of the snowpack.
Mammoth Pass snowpack, tracked on this graph by DWP, remained unmelted during California’s cool and wet spring for so long that by the time it started melting rapidly around June 10, it matched the mid-June snow water content for 1983, the wettest year on record!
This week, an unusually wet June storm dropped snow at the higher elevations and about a quarter inch of rain in Lee Vining. The cooler weather dramatically reduced the flows in many of the creeks, but very warm temperatures during the holiday weekend will result in another major peak flow during the middle of next week. The reservoirs in the Rush Creek watershed above Silver Lake will be full and with Grant Lake Reservoir spilling, Rush Creek will carry the extraordinary runoff all the way down to Mono Lake.
As of Monday, Mono Lake had risen 0.9 feet since April 1, and half a foot during the preceding three weeks. Another foot rise in July is not out of the question!