It’s that time of year again, when all eyes are on the Sierra snowpack, the level of Mono Lake, and spreadsheets.

How much will Mono Lake rise or fall this year? Photo by Andrew Youssef.

Just imagining this winter’s snowpack flowing down Mono Basin streams this spring brings a gleeful sigh of relief. But … spreadsheets? Yep, because spreadsheets, forecast models, experts, and in-depth Mono Basin hydrologic knowledge, when carefully woven together, are how we figure out the big question for Mono Lake: how much is the lake going to rise or fall this year?

You can see the full (more…)

In a winter full of snow, getting down to the lake has been a bit more challenging and a lot more fun.

A calm lake surface in not only incredibly scenic but ideal for lake level readings. With the onslaught of storms we’ve experienced this winter, a glassy lake has been a rare sight. Photo by Robbie Di Paolo.

The Mono Lake Committee monitors Mono Lake’s level throughout the year, at least once a month and usually more frequently. You can find monthly lake levels going back to 1971 here. The most important lake level reading of the year happens on (more…)

Wow! With 53.3″ of snowfall, February 2019 was Lee Vining’s snowiest February on record. The Lee Vining record begins in 1989, with the previous record 49.0″ of total snowfall in February 1998.

February 2019 was Lee Vining’s snowiest February on record, and included days when it was possible to ski along the shore of Mono Lake. Photo by Robbie Di Paolo.

Total snowfall for January and February 2019 was the third-largest on record with 78.5″, lagging behind the same time-frame in 2008 with 91.4″ of snow and 1993 with 81.2″ of snow. Snowfall this past February was 313% of average, and the January–February total was 209% of average. The (more…)

Peak snowmelt runoff on Mono Lake’s tributary streams is occurring!

Restoration Field Technician Robbie Di Paolo retrieves a temperature logging device in high flows on Rush Creek. Photo by Andrew Youssef.

Lundy Lake Reservoir is spilling, and the Rush Creek peak flow of 380 cubic feet per second (cfs) below Grant Lake Reservoir is being released over the next five days. So far, snowmelt runoff above the aqueduct has peaked at 272 cfs on Rush Creek, 238 cfs on Lee Vining Creek, 46 cfs on Parker Creek, and 23 cfs on Walker Creek. The flows should begin to subside soon given the rapid melting and limited snowpack. (more…)

Snow surveys conducted around every April 1st coincide with the average date of peak snowpack. This year, the surveys were completed at the end of March and revealed a large increase in snowpack over the previous month—from 50% of average to 76% of average!

Map of snow survey locations compiled by Robbie DiPaolo. The Lee Vining Creek watershed above the DWP diversion dam and the Rush Creek watershed above the SCE powerhouse are outlined in red.

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Last week the Los Angeles Department of Water & Power (DWP) released its preliminary runoff forecast based on record-breaking March 1st snow surveys: 195% of average runoff for the April 1, 2017 through March 31, 2018 runoff year. This volume of runoff is very similar to 1983, the wettest runoff year on record. Due to the warm storms in January and February, the lower-elevation snowpack below about 9,000 feet above sea level is much lower than in 1983, so we are assuming that record runoff is a high-end scenario. That forecast also assumes median precipitation over the next year.

Based on 1983 as a high end, 1995 as a probable scenario, and 2006 as a lowest possible scenario, we modeled the likely rise in Mono Lake based on those past year inflows and probable reservoir operations this year. The result? A 3.8-foot rise in Mono Lake is likely over the next year. Expected Grant Lake Reservoir operations add about half a foot to our forecast.

A 3.8 foot rise in Mono Lake is likely over the next year. (Click on the graph to enlarge it.) Graph by Greg Reis.

All three scenarios have little or no rise before May and a similar rise in May and June, since snow can only melt so fast, (more…)

After the wettest February since 1986 at some survey sites, Mono Basin snowpack is more than double the March 1st average!

Snow water equivalent (SWE) ranges between 205% and 244% of average at the five snow survey sites in the Mono Basin (called snow courses). Gem Pass, Ellery Lake, and Saddlebag Lake have the highest March SWE on record. At the lowest-elevation snow survey site—Gem Lake at 9,150 feet above sea level—SWE was about 10 inches shy of the 1969 record, but it had reached the 1983 amount. The Tioga Pass snow course was 5 inches shy of the 1983 record. In the map below showing the snow courses, portions of the Lee Vining Creek (top) and Rush Creek (bottom) watersheds are outlined.

At Ellery Lake and Saddlebag Lake, in the Lee Vining Creek headwaters, March 1st SWE was already higher than the record April 1st SWE set in 1983! Map by Robbie DiPaolo.

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February 1 snow surveys conducted over the past week revealed an approximately 200% of average snow water content in the Mono Basin. This puts the April 1 average at just over 120%.

The current outlook for April 1, 2017 peak snowpack at the Mono Basin’s five snow courses based on February 1 snow surveys and historic data. Graph by Greg Reis.

It is still early in the season, but even with a dry February and March, it will be an above-average year, and with an average end to the season it will be a wet year. With a wet February and March, new April 1 records could be set!

At the end of the wettest January in the 29-year record for Lee Vining, how do Mono Basin season totals for precipitation and snowfall compare to other years? The season precipitation total (since October) of approximately 15.84 inches of water is among the wettest years recorded since 1989. It is the second-wettest year to date (1997 was the wettest) that we’ve recorded in 29 years as of the end of January.

Lee Vining monthly precipitation. Graph by Greg Reis.

At Cain Ranch, five miles south of Lee Vining and more representative of the precipitation that falls on Mono Lake itself, the 2017 seasonal total of 9.44″ to date is sixth-wettest in 86 years. For both Cain Ranch and Lee Vining, these totals fall into the wettest 7% of years. (more…)

When Mono Lake is between 6377 and 6380 feet above sea level, and the final May lake level forecast (and any subsequent projections) shows that it will stay above 6377 feet, the Los Angeles Department of Water & Power (DWP) is permitted to export 4,500 acre-feet of water that year. Any time Mono Lake falls below, or is projected to fall below 6377 feet, exports must stop.

A blustery day in mid-October kicked up clouds of alkali dust over Mono Lake’s eastern shore. Mono Lake may drop below 6377 feet above sea level next year, which means no water may be exported to Los Angeles. Photo by Bartshe Miller.

Operations plan guidelines state that the water should be exported late in the summer, and this year, DWP exported this water September through early November, allowing more water to remain in Grant Lake Reservoir during the summer—a good thing that kept the reservoir higher during recreation season and likely kept water temperatures cooler for fish in Rush Creek. (more…)