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Hydrology | The Mono-logue

Posts Tagged ‘Hydrology’

DWP completes this year’s export of 4,500 acre-feet of water from the Mono Basin

Saturday, November 5th, 2016 by Greg, Information & Restoration Specialist
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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.

Photo by Bartshe Miller.

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…)

Fifth wettest October on record in the Mono Basin

Wednesday, November 2nd, 2016 by Greg, Information & Restoration Specialist
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At Cain Ranch, a precipitation station five miles south of Lee Vining that is representative of precipitation patterns on Mono Lake, October 2016 precipitation was 2.1 inches. This was the fifth-wettest October since 1931 and about 325% of average. Two of those other wet Octobers occurred in 2009 and 2010.

rainy-october-2016-10-30-north-basin-rainbow-elj_9161

October 2016 was also the sixth-wettest month at Cain Ranch in the last decade, and curiously three of those months were the Octobers mentioned above. The other three months that were wetter than October 2016 were December 2010 and 2012 and May 2015. Aside from the wet Decembers, this pattern is unusual, since December and January and February are usually the wettest months of the year.

The rain in the last week raised all the creek flows and also raised Mono Lake from 6377.12 to 6377.19 feet above sea level, putting it back on track with the lake level forecast DWP made in the spring.

A wetter but still below-average winter in the Mono Basin

Thursday, February 25th, 2016 by Greg, Information & Restoration Specialist
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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…)

Happy New Water Year 2016 from Mono Lake

Thursday, October 1st, 2015 by Greg, Information & Restoration Specialist
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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.

The remarkable thing about the 2015 water year was that it was the driest fall-winter on record and the wettest spring-summer on record.

The remarkable thing about the 2015 water year was that it was the driest fall-winter on record and the wettest spring-summer on record.

The Mono Basin’s wettest July since 1965

Thursday, July 16th, 2015 by Greg, Information & Restoration Specialist
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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.

The wet July continues the wet May-June centered on Mono County. This map from the Western Regional Climate Center shows April-June precipitation in percent of average.

This wet July continues the wet May–June centered on Mono County. This map from the Western Regional Climate Center shows April–June precipitation in percent of average.

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%.

Extreme precipitation amidst extreme drought

Friday, July 3rd, 2015 by Greg, Information & Restoration Specialist
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On the evening of July 1st, rain falling on Mono Lake during thunderstorms could be heard two miles away. Photo by Geoff McQuilkin.

On the evening of July 1st, rain falling on Mono Lake during thunderstorms could be heard two miles away. Photo by Geoff McQuilkin.

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…)

Mono Lake’s wet May keeps on keeping on

Saturday, May 23rd, 2015 by Greg, Information & Restoration Specialist
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Clouds have covered the Mono Basin for much of the last three weeks. Mono Lake on May 20. Photo by Arya Degenhardt.

Clouds have covered the Mono Basin for much of the last three weeks. Mono Lake on May 20. Photo by Arya Degenhardt.

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…)

Wet weather causes Mono Lake to rise

Friday, May 15th, 2015 by Greg, Information & Restoration Specialist
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After the storm clouds cleared last Friday, Black Point had turned white under 14 inches of new snow. Photo by Lisa Cutting.

After the storm clouds cleared last Friday, Black Point had turned white under 14 inches of new snow. Photo by Lisa Cutting.

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.

2015 will be the driest year on record, by far

Wednesday, April 29th, 2015 by Greg, Information & Restoration Specialist
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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.

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 the 1977 runoff.

The twelve driest seasons on record in the Mono Basin. 2015 April–September runoff is not only going to be less than 1977, the driest year on record—it is also expected to be less than half of the 1977 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 measured

Friday, April 3rd, 2015 by Greg, Information & Restoration Specialist
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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).

Tioga Pass snowpack has a March decline about 13% of the time. Similar years are shown, with average and 2014 shown for comparison.

Tioga Pass snowpack has a March decline about 13% of the time. Similar years are shown, with average and 2014 shown for comparison.

Gem Pass snowpack has a March decline about 17% of the time. Similar years are shown, with average and 2014 shown for comparison.

Gem Pass snowpack has a March decline about 17% of the time. Similar years are shown, with average and 2014 shown for comparison.

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).

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