RUNOFF HEATS UP
Weekend temperatures slated to top 105 in the Owens Valley and hit 85-plus in Mammoth Lakes should generate enough daytime and nighttime heat to deliver this year’s “peak” Sierra runoff.
At least, that’s the prediction from the snow and water-watchers at the Los Angeles Department of Water and Power (LADWP). And this time they are pretty confident streams from Lee Vinning to Lone Pine will be surging to their highest levels of the season. Granted, the “peak” runoff was initially supposed to hit sometime in late June, then the July 4th weekend was supposed to deliver the final blow to the Sierra’s record snowpack. But each time, the slight drop in temperatures slowed the melt in the high Sierra and gave LADWP time to continue to fortify its water-moving infrastructure.
It’s not like LADWP officials are complaining about the extended runoff season. The slow, steady melt has given LADWP extra time to manage this year’s record runoff that will be 233% of normal (from a record snowpack at 296% of average).
After an unusual winter featuring unrelenting snowstorms, spring was also off script. Typically, snowpack peaks on April 1 and starts a quick melt to basically disappear by mid-June. Not this year. At a recent Inyo-LA Technical Group meeting, Eric Tillemans, LADWP aqueduct manager, said this spring featured temperatures from 5 to 10 degrees cooler than average in April, May and June. That weather weirdness has pushed the peak melt back into mid-July in most of Inyo County, if not later in Mono County.
Cool is still not cold, however. Since the end of May, stream levels in Inyo County have been surging at what would usually be “normal” runoff levels. In Mono County, the stream flows were a bit more restrained, but have picked up considerably since mid-June.
The spell of high water, with dozens of creeks and streams running bank-to-bank, and many coursing out of their banks for nearly two months, begs the question: “How much snow is left up there?”
The quick answer: Plenty.
Here’s the longer answer, from a July 11 Facebook report from the Inyo County Search and Rescue team: “Most of the Sierra in Inyo County still has patchy snow between 9,000 and 10,000 feet, and almost full snow coverage above 10,000 feet.”
Still need convincing? Check the Mammoth Mountain webcam for Chair 23. Or photos of the snow-clad mountains above Virginia Lakes, which sit just above 9,000 feet, or the CHP rescue helicopter sitting at trail camp at 12,000 feet just below Mt. Whitney during yet another rescue on July 11.
The staggered runoff season has allowed LADWP to make room in its reservoirs for the coming snowmelt.
Tillemans noted that Long Valley Reservoir (Crowley Lake) is still about 10 feet below capacity and has room to handle incoming runoff from the Owens River and Hot and McGee creeks. The outflows from Crowley have dropped to a minimal 100 cubic feet per second, he added, which has had a cascading effect all the way to Owens Lake.
The lower flows into Pleasant Valley Reservoir have dropped the reservoir levels below capacity for the first time in months. That means slightly lower flows in the Owens River going through Bishop. But the river and adjacent canals are still running fast and full, so keep those inner tubes in the garage for now.
Bishop Creek, however, could still be a trouble spot. California Edison has been allowing runoff to fill its reservoirs (South Lake, Lake Sabrina and Intake II), Tillemans said. Bishop Creek, which is running at a 500 cfs clip, could surge even higher once those reservoirs hit capacity and start spilling water into the creek.
The lower flows in the Owens River also translate into less water going into the Lower Owens River Project. The LORP was essentially the relief valve for excess runoff, and at one point saw flows topping 700 cfs a day. That flooded the valley floor from Aberdeen to the Owens Lake. Currently, the LOPR flows are about 300 cfs.
Owens Lake has been transformed into a real lake from the excess runoff streaming into the lakebed.
The middle of the lake is now a huge, blue expanse of water. The sight of “The Owens Dry Lake” brimming with water has stunned and delighted locals and visitors alike.
In general, Tillemans said the department expects creeks and streams to hit peak levels, but not the Owens River. The peak flows should start in the south, at Cottonwood Creek, Lone Pine Creek and Independence Creek, then work north though the rest of Inyo County and into Mono, Tillemans noted.
That also holds for the streams feeding Mono Lake. About mid-June, the four creeks emptying into Mono Lake started roaring.
Lee Vining Creek hit 560 cfs on July 3 and Rush Creek was at 615 cfs on the sameday.
Over the past week, Mono Lake has been absorbing about 1,300 cfs a day.
For comparison, the LA Aqueduct ships a mere 700 cfs south to Los Angeles.
As predicted, Mono Lake is on the rise, thanks to the abundant runoff. On July 12, it hit 6,382 feet above sea level, which means it has risen a solid two feet in the past month.
