The strong 2015–2016 El Niño winter is likely to turn out below-average in the Mono Basin. The 90% of average February 1st snowpack, and an 80% of average preliminary runoff forecast based on that snowpack, were followed by a dry February. In the next week, March 1st snow surveys will reveal how bad things are. A wet March might be able to catch things back up to average, but it would take a very wet spring to shift the snowpack and snowmelt runoff above average at this point. From 1980–2010, the lowest March snowpack that resulted in above-average runoff was 110%. (more…)
Recent updates on the Mono Basin Clearinghouse include the following items:
Point Blue has finished its 2015 report on the nesting success of California Gulls at Mono Lake. According to project coordinator Kristie Nelson, it was an above-average year—a welcome finding after a downward trend of below-average populations over the last ten years.
October 1st marks the start of a new water year. The 2016 water year runs October 1, 2015–September 30, 2016. It measures the fall-winter precipitation and the rain that falls in the following growing season all in one 12-month period.
Here is how last year stacks up for Lee Vining precipitation: 11.84 inches, or 84% of average. The remarkable thing is that the fall-winter was the lowest on record, at only 34% of average, meaning the snowpack was the lowest on record. Summer was highest on record, at 285% of average.
At the Cain Ranch weather station, five miles south of Lee Vining, as of July 13, 1.57 inches of rain had fallen in July. That makes this month already the second-wettest July on record after the 1.98 inches of rain in July 1965. Records at this location began in 1931. Rain fell on all but two days between July 1 and 10, and while it has been dry there since July 10, it still has been raining in other parts of the Mono Basin almost every day.
Lee Vining Creek above the Los Angeles Department of Water & Power (DWP) diversion dam experienced its peak flow of about 124 cubic feet per second on July 11, from rain and melting fresh snow. Below the dam, the minimum flow is being released, and the floodwaters are being diverted to Grant Lake Reservoir, which has been slowly rising since May.
Aside from brief floods due to thunderstorms, the Mono Basin’s creeks are dropping to the very low levels that were otherwise expected this summer. If the thunderstorms stop, we will start seeing new low flow records later this month, especially in watersheds without glaciers, such as Walker Creek. The April–September snowmelt runoff forecast issued by DWP in May predicted 19% of average runoff, with a lower bound of 7% and an upper bound of 32%. Nineteen percent is less than half of the runoff measured in 1977, the driest year on record; 32% is still much drier than the driest year on record. Thanks to the recent wet weather, Mono Basin runoff is on track to reach 32%.
The Mono Basin is a land of extremes, and this year’s weather is no exception. Temperatures since January are the warmest on record. October–March precipitation in Lee Vining was the lowest on record. April–September precipitation, on the other hand, already is the highest on record—and we are only halfway through that time period! This water year (October 1, 2014–September 30, 2015) is the first time Apr–Sept precipitation has exceeded Oct–Mar. This reversal of the warm and cold season Mediterranean precipitation patterns has allowed invasive plants like cheatgrass to (more…)
A week ago, at mid-month, we excitedly were tallying up the already-record-making Mono Basin precipitation totals for May and the rise in Mono Lake. Who would have thought that it would keep raining and snowing—especially during the driest year of one of the worst droughts on record?
Well, it has kept raining and snowing! (more…)
With May only half over, we have measured almost three inches of precipitation in Lee Vining—surpassing the usual total for all of April-September. This May has already beaten the previous records of 2.23 inches measured in May 1989 and 2.74 inches measured in May 1994. It has also been cold, with over 16 inches of snow already beating the 14.6 inches measured in May 1994. At Cain Ranch, it is already the third-wettest May since 1931.
As Rush Creek above Grant Lake Reservoir nears record-low flows for May, record highs for precipitation are welcome.
A cold May with 400% of average precipitation is very good news for Mono Lake. Reduced evaporation helps slow the declining lake level, and direct precipitation on the lake a week ago raised the level about a tenth of a foot. It now stands at 6379.0 feet above sea level, about a tenth of a foot higher than it was on May 1st. Mono Lake is projected to drop a tenth of a foot this month, but it is now looking like it will remain steady, and it could even have a net rise if the last half of the month is wet.
October to March precipitation was 33% of average—driest on record for Lee Vining and third-driest on record for Cain Ranch. The April 1 snow surveys found only 14% of average snow water content in the Mono Basin after a warm March melted much of the already near-record-low snowpack.
Based on precipitation, snowpack, and recent runoff, the Los Angeles Department of Water & Power (DWP) has run its forecasting equations and issued its runoff forecast: 19% of average runoff is expected for April–September, and 25% over the next year—assuming median precipitation falls. 2015 April–September runoff is not only going to be less than 1977, the driest year on record—it is expected to be less than half of 1977’s runoff.
We are in uncharted territory. It has not been this dry since records began in the Mono Basin. This will be a challenging year for our ecosystems and for water management.
Warm March took snowpack to lowest levels on record; Tioga Pass and Gem Lake have biggest March declines ever measuredFriday, April 3rd, 2015 by Greg, Information & Restoration Specialist
Yesterday I was refreshing the California Cooperative Snow Surveys Webpage almost every hour. Over and over again I saw the dramatic pattern across the state—higher double-digit percentages at the highest elevations of almost every watershed, and lower or zero snowpack at the lower elevations.
Finally, this morning, the rest of the Mono Basin data appeared! The good news is that the snowpack in most of the Mono Basin isn’t as bad as the 6% of average at Tioga Pass and Saddlebag Lake. The bad news is that with only 14% of average snow water content, the snowmelt runoff will be lower than anyone anticipated.
Gem Pass, at the highest elevation, tops the charts with 25% of average snow water content. Everywhere else, snow surveyors measured the lowest snow water content ever measured on April 1st. Ellery Lake is 21% of average, and Gem Lake is 12% of average. Also in the Mono Basin, but reported under the San Joaquin River drainage, is Agnew Pass, which lost 7.5 inches of water in March, and currently is only 3% of average (1 inch of water content).
The following is a summary of the five Mono Basin snow courses:
- Gem Pass lost 2 inches of water in March, and at 8.5″ is about the same as 1977, although not as dry as 1931.
- Gem Lake lost 5.5 inches of water in March, and at 3.5″ is driest on record (beating 5.9″ in 1976).
- Tioga Pass lost 6 inches of water in March, and at 1.5″ is driest on record (beating 7.4″ in 1977).
- Saddlebag Lake lost 6 inches of water in March, and at 2″ is driest on record (beating 9.9″ in 1977).
- Ellery Lake lost 1.5 inches of water in March, and at 6″ is driest on record (beating 9.7″ in 1977).
As early as late February, it seemed likely that this was going to be the driest year on record. Mono Basin snowpack was lower than any year but 1991, and that year had a “Miracle March” that was absent from the long-range forecasts. Sure enough, the dry pattern didn’t change, and March was very dry.
On Thursday I began checking the snow surveys web page for the April 1st snow survey results, which are conducted within a few days of April 1st. On Friday, results for one of the five Mono Basin “snow courses” appeared. And it was a shocking result: Tioga Pass snow water content is at only 6% of average. (more…)