California weather extremes and climate

[Xulonn]

Looking at NOAA's California Nevada River Forecast Center interactive map [http://www.cnrfc.noaa.gov/], the only red dot (indicating flooding) I see in the entire included region is near the mouth of the Navarro River at the central Mendocino County coast.  This is one of those local, short north coast redwood/douglas fir forest rivers in rugged terrain that is not dammed, and not important with respect to the state's drought.  Most other NorCal rivers are predicted to rise significantly, but remain well below flood levels. 

[Sigmetnow]

NWS Sacremento:  Some very impressive snowfall totals since Friday!  More storms expected later this week! #cawx
https://twitter.com/nwssacramento/status/707017393948663808

[Sigmetnow]

A month and many storms later, yet the California mountain snowpack is barely hanging on, especially in the warm south.

Compare with Feb 16:
https://forum.arctic-sea-ice.net/index.php/topic,729.msg70121.html#msg70121

Or choose your own dates at: http://cdec.water.ca.gov/cdecapp/snowapp/sweq.action

[Sigmetnow]

Pacific Institute:  The California Drought:  Current Conditions

A recent snow survey showed statewide snowpack at 83% of the March 1st average. Unless California receives heavy rain as much as it did during the “March Miracles” of 1991 and 1995, drought conditions will persist for another year.

-The California and Oregon Departments of Fish and Wildlife estimated that the population of the fall run Chinook salmon in the Klamath River is about a third of last year’s estimate and the second lowest predicted since 1996. The low prediction number is based on the combined effects of climate change and the ongoing California drought. Meanwhile, delta smelt count has hit the lowest level ever recorded for January and February.
...
-A new study by NASA, Scripps Institution of Oceanography at UC San Diego, and other partners found that atmospheric river storms in California’s Sierra Nevada are 2.5 times more likely than other types of storms to accelerate the melting of snow, with warmer rain falling on snowpack and causing it to melt.

-LA County is using cloud seeding technology to increase the amount of rainfall from existing clouds. Under the right atmospheric conditions, the method can produce 10-15% more rainfall, according to a county estimate.
...
–A proposed ballot initiative to support the construction of new reservoirs and water storage projects in California has sparked a new debate on the state’s priorities. The ballot initiative would shift $8 billion from the high-speed rail project to a newly created agency, the State Water Storage and Groundwater Storage Facilities Authority. It would also shift $2.7 billion from the water bond approved in November 2014 to the new authority to improve water supplies.

http://www.californiadrought.org/drought/current-conditions/

[Laurent]

The Terrifying Beauty Of California’s Wildfires Captured In Stunning New Time-Lapse Video
http://www.huffingtonpost.com/entry/california-wildfire-time-lapse-video_us_56ef8f7de4b084c67220b57b?ir=Green&section=us_green&utm_hp_ref=green

California’s five-year drought created the perfect conditions for massive wildfires, which have left behind stunning and heartbreaking images of devastation.

Filmmaker Jeff Frost has been documenting these fires, and just released a time-lapse video that reveals the raw power of nature at its hottest.

“I wanted to show what we are up against right now, let alone down the road when global warming intensifies heat and drought which will further exacerbate wildfires,” Frost told National Geographic.

Last year, Frost documented his escape from a wildfire in a HuffPost blog, and included a time-lapse video of his drive out of the area after the worst of the blaze had passed.

“It felt like I was taking a drive through Dante’s Inferno,” he wrote.

[Sigmetnow]

April 1 (the start of the water year) Sierra Snow Pack data is out.
% of April 1 average:  86%

Southern Sierra:  73%.

So much for the El Niño rebound everyone was hoping for. 

[ghoti]

Well it is less below average than it was before 

[Sigmetnow]

Eric Holthaus: Latest NMME shows all-in on La Niña. Most certainty I've seen so far, despite current low-predictability window.
https://twitter.com/ericholthaus/status/718506175310868480

[Sigmetnow]

Eric Holthaus: All 7 components of latest NMME show a dry start to the 2016-17 rainy season in California, thanks to La Niña.
https://twitter.com/ericholthaus/status/718505369119498240

[Sigmetnow]

Eric Holthaus: Still looking like this summer is going to be a hot one (coast to coast) as El Niño transitions to La Niña.
https://twitter.com/ericholthaus/status/718507680717873153

Eric Holthaus: Atlantic & Gulf temperatures during the peak of this year's hurricane season (Aug-Sep-Oct) looking toasty warm.
https://twitter.com/ericholthaus/status/718521490971308032

[Sigmetnow]

Eric Holthaus: Here's Aug-Sep-Oct ocean temperatures during the peak of this year's Atlantic hurricane season....
https://twitter.com/ericholthaus/status/718526988294553600

[Sigmetnow]

U.S. Seasonal Drought Outlook - May-June-July

Latest Seasonal Assessment - As the wet season nears its end in the West, coincident with the waning El Niño, a return to climatologically dry conditions is favored across the region. Though the final drought-related statistics for California are still being determined, it appears that northern portions of the state fared well this past winter season in such areas as precipitation, snowpack, and reservoir levels.

Southern California did not fare as well, despite the presence of one of the strongest El Niño's on record. Late season precipitation was indeed welcome in southern California, but unfortunately, significant moisture deficits remain. Much of the Desert Southwest also missed out on anticipated El-Niño related precipitation this past winter. During the next two weeks, above-median precipitation is favored across portions of California, the Great Basin, and the Southwest. However, the heaviest precipitation is expected to occur outside the ongoing drought areas. For the upcoming May-June-July (MJJ) season, drought persistence is forecast for most areas west of the Continental Divide....

http://www.cpc.ncep.noaa.gov/products/expert_assessment/sdo_summary.php

[Sigmetnow]

Update on the California Drought – May 10, 2016
 
This week in… Water Conservation Continues, But With a Twist

The State Water Resources Control Board (the State Board) recently released a proposal to amend the extended emergency water conservation regulations (adopted February 2, 2016) due to improvements in water supply conditions throughout the state. Significant proposed changes include replacing statewide standards with locally developed conservation targets. Individual urban water suppliers would be required to self-certify that they have sufficient water supplies and to reduce potable water use in a percentage equal to their projected shortfall, assuming three additional years of drought....
...
— The US Forest Service estimated that 27.6 million tree deaths in 2015, up from 3.3 million in 2014. Drought and the spread of bark beetles are the main causes of these tree deaths.

http://www.californiadrought.org/drought/current-conditions/

[abbottisgone]

April 1 (the start of the water year) Sierra Snow Pack data is out.
% of April 1 average:  86%

Southern Sierra:  73%.

So much for the El Niño rebound everyone was hoping for. 

Is this not a major improvement over the last few years?

[Sigmetnow]

April 1 (the start of the water year) Sierra Snow Pack data is out.
% of April 1 average:  86%

Southern Sierra:  73%.

So much for the El Niño rebound everyone was hoping for. 

Is this not a major improvement over the last few years?

Indeed it is: Last year at this time the numbers were 1% of April 1 average and 2% of normal for the date. But everyone was hoping for an above average season this year, to really help things out.

After an encouraging start to 2016, snow levels have decreased to 32% of April 1 and 51% of normal for the date.   The good news: current reservoir storage is up from recent storms and melting snow.

Unfortunately, too much water all at once brings other problems:
California's largest reservoir filling too fast thanks to El Niño, must release more water
http://www.latimes.com/local/lanow/la-me-ln-california-reservoir-too-full-el-nino-20160325-story.html

[Sigmetnow]

@Weather_West: #LaNina does NOT always bring dry CA winters. However, models hint at increased risk this yr. #CAwx #CAdrought
https://twitter.com/weather_west/status/730891265617731584

[Sigmetnow]

Eastern Pacific Hurricane Season Begins May 15; How the Storms Can Threaten the U.S.

Why are tropical storm and hurricane landfalls such a rare event in Southern California? The primary reason is the very cool ocean temperatures in the path of a tropical system trying to make the journey to the Pacific coast of the United States. As in 1858, the hurricane must be moving fast enough, over waters just warm enough, to maintain its intensity on the way north to California.

https://weather.com/storms/hurricane/news/eastern-pacific-hurricane-season-forecast-us-threat-2016

[Sigmetnow]

Eric Holthaus:  A threat to snowpack: Jan-Apr temperatures on the rise in California.
https://twitter.com/ericholthaus/status/733338298098155520

Current California snowpack has melted down to 20% of April 1 average, 36% of normal for May 16.

[solartim27]

Current California snowpack has melted down to 20% of April 1 average, 36% of normal for May 16.

So this should be filed under the Human Stupidity thread?  I'm sure it will work out fine.  My son chose a college out of CA, and I did not try to stop him.

http://www.sfgate.com/bayarea/article/California-poised-to-end-unprecedented-water-7654512.php

State officials, in a policy shift that reflects California’s easing drought conditions, decided Wednesday to scrap the emergency conservation mandates that have forced cities and towns to cut water use as much as 36 percent, often by hitting residents with unprecedented restrictions and fines.

Instead, the State Water Resources Control Board will allow urban water providers to set their own water-reduction targets based on their own customers’ wants and needs.

[Sigmetnow]

We’re in Year Five of California’s Drought

...For Southern California especially, the drought is still just as bad as ever. In much of the Sierra Nevada and Southern California, there’s still two or three entire years of rain missing since this drought began five years ago.
...
This winter’s chaos has caused Cohen to lose a bit of confidence in using past El Niño patterns to predict future El Niño patterns, he says. Even though this El Niño was one of the strongest on record, “impacts-wise, this winter was classical La Niña.” Cohen thinks he’s found a big reason why: This winter featured sharply fluctuating strength of the polar vortex, which in its strong phase tends to pull the Pacific jet stream northward. That, combined with the steady pressure of a gradually warming tropics, might have done the trick.

Whatever the reason for the weird El Niño on the West Coast, the result is Southern California remains locked into its worst drought on record. Going into the state’s six-month dry season, for the near-term at least, fire conditions there are only going to get worse.

http://www.slate.com/articles/health_and_science/science/2016/05/lackluster_el_ni_o_has_set_california_up_for_terrible_forest_fires_this.html


Edit:

Eric Holthaus:  Since I drafted this article two days ago, California snowpack is down from 35% of normal to just 27%.
https://twitter.com/ericholthaus/status/733736565877268480

[Bruce Steele]

Lake Cachuma is the main reservoir that supplies Santa Barbara, Goleta and all the south county cities of Santa Barbara county. It also supplies the downstream cites of Solvang, Santa Ynez ,Lompoc and Buellton as well as the downstream riparian agricultural water rights holders. Lake Cachuma will shrink to dead pool status within the next six months. Although Montecito has mandatory water restrictions in place there aren't any other mandatory water restrictions to deal with the loss of the major water source for hundreds of thousands of county residents. There are wells drilled into deep aquifers and also connections into the state water system for some cities and Santa Barbara is constructing a desalinization plant but considering the gravity of the situation you would think there might be public meetings or warnings about our impending disaster in paradise. Not so!  Those of us who pull
riparian water from shallow wells into the Santa Ynez river will have to deal with a river that hasn't gone dry in sixty years. There are thousands of acres of grapes and agricultural crops that were not there sixty years ago . There are thousands of houses with lawns and swimming pools that are going to have to adjust to the rather dire water conditions soon to be upon us. You might think regulators might conserve some of the water remaining in the reservoir but I am an agricultural user and there haven't even been requests to conserve issued . There aren't even meters required on our wells.
 I look at the prospects of my wells going dry and the value of my farm falling to values dry land might bring. It will rain again someday but hauling water to supply my small household is going to be a challenge. My farm animals will be culled or moved and anyone with millions invested in vineyards is going to loose their ass. The whole situation reminds me of how we as a society are currently dealing
with climate change. Three monkeys with eyes , ears and mouth covered . Government is not capable of dealing with reality here in the land of milk and honey.       

[Sigmetnow]

Click on the other pages at the bottom of the linked article for details on the specific counties.

Counties Most Battered by the Drought

Currently nine counties have at least 60% of their total area in a state of exceptional drought. During periods of exceptional drought, losses of crop or pasture as well as water shortages and restrictions are widespread.

In an interview with 24/7 Wall St., Brad Rippey, agricultural meteorologist with the U.S. Department of Agriculture, explained that the California winter was indeed a boon for the northern part of the state. “Now, you go to the southern end of the state and it’s like a whole different world. They did not get any sustained precipitation there, and so roughly from the San Joaquin Valley southward there are still major issues in California with reservoirs and rivers.”

As the hottest, driest months approach, Southern California braces for further worsening of already historically poor conditions. Most of these counties have been in a state of exceptional drought for almost 30 straight months. The prolonged drought has dried the lakes and wells around the state, and municipal water reservoirs are at just a fraction of their capacity.

Several of these counties are located in California’s San Joaquin Valley, which is one of the world’s most productive agricultural regions, and these county economies disproportionately rely on farming. While just 2% of the nation’s workforce is employed in agriculture, at least 10% of the workforce is employed in agriculture in four of these counties.

http://247wallst.com/special-report/2016/05/21/counties-most-battered-by-the-drought/

[Sigmetnow]

Aerial Images Show Decades of Foothill Forest Growth Erased Due to California’s Extreme Drought

"NASA's satellite record offers abundant evidence that extensive tree die-back from the historically low water years of 2013 to 2015, combined with numerous large stand-replacing wildfires in the Sierra region, has essentially reversed the impressive accumulation of live tree density state-wide that we were tracking since the early 1980s,” said the study's lead author, Christopher Potter of Ames.

Three decades of forest growth was erased by the drought's impacts over much of the lower-elevation Sierra Nevada mountain region in the past couple years.

http://www.nasa.gov/feature/ames/aerial-images-show-decades-of-foothill-forest-growth-erased-due-to-california-s-extreme

[Sigmetnow]

June 1:  Snowpack is 23% of normal for the date.  7% of April 1 average.

[ritter]

June 1:  Snowpack is 23% of normal for the date.  7% of April 1 average.

Well, that's still a whole lot better than last year, dismal as it is.

[Sigmetnow]

In just the past week, snowpack has melted to 2% of the April average, 9% of normal for the date.
The Southern Sierra is essentially bare.

[Sigmetnow]

El Niño is dead, leaving behind legacy of a heated planet, devastated corals and monster storms

While El Niño can be implicated in weather and climate extremes all over the world, it did not deliver in the one place which perhaps needed it to the most.  While it was forecast by many to deliver heavy rainfall in Southern California — mired in a multi-year drought — the rain really never came.

“Instead of torrential rain in Southern California (and the mudslides that came along with it), the region ended winter with well-below average precipitation,” wrote The Post’s Angela Fritz. “Even worse, California statewide snowpack was just 87 percent of average at its peak. It’s true that this year’s snowfall was a huge improvement over the previous winter, but the amount of water stored in the snow has fallen short of what was hoped for, and even expected, due to a very strong El Niño.”

https://www.washingtonpost.com/news/capital-weather-gang/wp/2016/06/09/el-nino-is-dead-leaving-behind-legacy-of-a-heated-planet-devastated-corals-and-monster-storms/

[Sigmetnow]

Central and Southern Sierra snowpack are now toast.  1% of April 1 Average, and 25% of the Average for the date, is left.

[Archimid]

While El Niño can be implicated in weather and climate extremes all over the world, it did not deliver in the one place which perhaps needed it to the most.  While it was forecast by many to deliver heavy rainfall in Southern California — mired in a multi-year drought — the rain really never came.

I think it did deliver. Snow pack was very high back in April, but the hotter than average temperatures melted it.

[Sigmetnow]

While El Niño can be implicated in weather and climate extremes all over the world, it did not deliver in the one place which perhaps needed it to the most.  While it was forecast by many to deliver heavy rainfall in Southern California — mired in a multi-year drought — the rain really never came.

I think it did deliver. Snow pack was very high back in April, but the hotter than average temperatures melted it.

The precipitation data at: http://www.cnrfc.noaa.gov/monthly_precip.php
seems to show that while a few areas received above-average precipitation, most places received only about average -- and the central and southern coastal areas had quite a deficit.

[Sigmetnow]

California's drought isn't over. Why are so many water agencies ending mandatory conservation?

Coachella Valley residents have slashed their water use nearly 25 percent over the past year in response to California's historic drought. Now they face a new conservation mandate: zero percent.

No, the drought isn't over: The entire state is abnormally dry and 43 percent of it suffers from "extreme" or "exceptional" drought, according to the U.S. Drought Monitor. But with California's reservoirs and snowpack in better shape than last year after a moderately wet winter, Gov. Jerry Brown ordered the state water board to relax the strict conservation targets it imposed last June.

The water board had previously required parts of the Coachella Valley to cut back by as much as 36 percent, compared to 2013 levels. But last month, the board told urban water suppliers to calculate their own targets, based on local water conditions. All six Coachella Valley water suppliers sent their calculations to the state this week, and they reached the same conclusion: The valley's underground aquifer has more than enough water to withstand several more years of drought, so no mandatory conservation is necessary under the state's formula.

That also means golf courses — which have been responsible for a quarter of the Coachella Valley's groundwater pumping in recent years — are no longer legally obligated to use less groundwater.

"This isn’t OK," said Peter Gleick, president of the Pacific Institute, a water think tank in Oakland. "I just think all of this is the wrong message to be sending.”

http://www.desertsun.com/story/news/environment/2016/06/23/californias-drought-isnt-over-so-why-so-many-water-agencies-ending-mandatory-conservation/86244464/

[Sigmetnow]

33 new dry wells in Tulare County, California, this week. 638 total.
http://tularecounty.ca.gov/emergencies/index.cfm/drought/drought-effects-status-updates/2016/august/week-of-august-8-2016/

[Sigmetnow]

Bill McKibben:  As El Nino concludes, 100% of California is in drought, which is a fairly substantial percentage
https://twitter.com/billmckibben/status/774273051630247936

[solartim27]

Don't be such a worry-wart.  Everything is fine here in CA, this winter will be really wet, I promise.  Oh, and there isn't any zika in FL either.
(http://www.miamiherald.com/news/health-care/article100939277.html)

(Where's that damn sarcasm font button?)

[Jester Fish]

Son of Blob/Return (Continuation!) of Drought
http://cliffmass.blogspot.com/2016/09/the-blob-is-back.html

[JimD]

The long term prognosis is that CA and the southwest will remain in drought for the duration of the Anthropocene.

Pacific Ocean's response to greenhouse gases could extend California drought for centuries

Clues from prehistoric droughts and arid periods in California show that today's increasing greenhouse gas levels could lock the state into drought for centuries, according to a study led by UCLA professor Glen MacDonald.

The study, published today in the Nature.com journal Scientific Reports, looked at how natural climatic forces contributed to centuries-long and even millennia-long periods of dryness in California during the past 10,000 years. These phenomena—sun spots, a slightly different earth orbit, a decrease in volcanic activity—intermittently warmed the region through a process called radiative forcing, and recently have been joined by a new force: greenhouse gases.
As long as warming forces like greenhouse gases are present, the resulting radiative forcing can extend drought-like conditions more or less indefinitely, said MacDonald, a distinguished professor of geography and of ecology and evolutionary biology.

"Radiative forcing in the past appears to have had catastrophic effects in extending droughts," said MacDonald, an international authority on drought and climate change. "When you have arid periods that persist for 60 years, as we did in the 12th century, or for millennia, as we did from 6,000 to 1,000 B.C., that's not really a 'drought.' That aridity is the new normal."
.....

The point will come in the not to distant future where the amount of food producible in CA will plummet. 

http://phys.org/news/2016-09-pacific-ocean-response-greenhouse-gases.html

[Sigmetnow]

Mount Wilson Observatory has completely run out of water
Drought causes shutdown of fountains and restrooms
http://la.curbed.com/2016/10/9/13203068/mount-wilson-observatory-has-completely-run-out-of-water

[Sigmetnow]

State on 'yellow alert' as savings drop

Two months after most water providers were allowed to ditch their mandatory conservation targets, California’s efforts to save water appear to be heading in the wrong direction.

Water conservation tapered off again in San Joaquin County and across the state in August, prompting state officials to warn that the targets could be put back in place beginning next year.

http://www.recordnet.com/news/20161005/state-on-yellow-alert-as-savings-drop

[Sigmetnow]

Eric Holthaus:  After 181% of normal precip this rainy season, most big California reservoirs are full—BUT—warm weather means snowpack just ~61% of normal.
https://twitter.com/EricHolthaus/status/813781444652859393
(Graphs and maps at the link.)


Daniel Swain:  Greatly reduced snowpack, especially at lower elevations in Sierra Nevada, becoming a staple of California's increasingly warm winters.#CAwx
https://twitter.com/EricHolthaus/status/813782383619166208

[ritter]

Those not familiar with California hydrology, snowpack represents our largest reservoir to get us through the summer.

[Sigmetnow]

California releases report on disputed twin tunnels water plan

It takes a while to get to the point, but an 80,000-page environmental opus released Thursday makes the case that Gov. Jerry Brown’s $15.7 billion twin tunnels project is the best way to fix California’s water woes.
...
The report analyzed the environmental impacts of 18 ideas — including doing nothing — to fix the sprawling state and federal water system that delivers supplies to 25 million people across California and irrigates some 3 million acres of farmland.

http://www.sfgate.com/bayarea/article/California-releases-80-000-page-report-on-10814395.php

[Sigmetnow]

Dangerous atmospheric river event will impact California this weekend.

Eric Holthaus:   Mudslides, debris flows possible in recent burn scars in the Sierras due to heavy rain & rain-induced snowmelt this weekend.
#climatechangeD

NWS Hanford:  Video weather briefing has been published for this weekend's high-impact #AtmosphericRiver event. ... #CAwx

Video:  https://m.youtube.com/watch?v=3u7hPB4D_5Q&feature=youtu.be

https://twitter.com/ericholthaus/status/817090713439629312


Eric Holthaus:  This is a huge issue. Some parts of the Sierras will actually *lose* snowpack during this storm, adding to the already severe flood threat.

Daniel Swain:  Very high 850mb temps during most intense precip could lead to dramatic snowmelt in Sierra Nevada. Major flood concerns. #CAwx #CAflood

https://twitter.com/ericholthaus/status/817086389472940032

[Sigmetnow]

“Today we have building codes for earthquake safety, but millions of new westerners are not aware of the region’s calamitous climate history. Most have never even heard of the 1861–62 floods, and those may not have been the worst that nature can regularly dish out to the region.”

California Megaflood: Lessons from a Forgotten Catastrophe
A 43-day storm that began in December 1861 put central and southern California underwater for up to six months, and it could happen again
https://www.scientificamerican.com/article/atmospheric-rivers-california-megaflood-lessons-from-forgotten-catastrophe/

[Sigmetnow]

NWS Reno:  Atmospheric River has arrived. Heavy rain & flood impacts expected Satellite/radar show deep tropical moisture with this storm.  #NVFlood17
https://twitter.com/nwsreno/status/817999031104311296

Radar clip at the link.

[Sigmetnow]

Flooding in southern California burn scars leads to mudslides.

Southern California storms raise fears of mudslides, trigger evacuations

LOS ANGELES -- California residents evacuated neighborhoods below hillsides scarred by wildfires as the third - and largest - in the latest series of storms brought powerful rain Sunday and warnings about flash flooding and possible mudslides.

The National Weather Service warned that the system was expected to gain strength throughout the day and could be the strongest in at least seven years. Flash flood watches and warnings were in effect for swaths of greater Los Angeles, where mountain areas could see more than 2 inches of rain.

Authorities ordered evacuations near wildfire burn areas in Santa Barbara, Los Angeles and Orange counties. Officials said potential debris flows could restrict access for emergency responders. ...

http://www.cbsnews.com/news/southern-california-storm-fears-of-mudslides-triggers-evacuations/

[Sigmetnow]

More than half of California still experiencing moderate to extreme drought conditions, according to U.S. Drought Monitor.
http://www.californiadrought.org/drought/current-conditions/

[Shared Humanity]

It is still a dramatic improvement. Hopefully this does not cause the state and its residents to relax. California must still address its long term problems regarding water.

[Sigmetnow]

Why Is the Drought Not Over Yet?

Experts say groundwater needs to be replenished and that this could take one or two more seasons of equivalent rains.
...
The only areas with extreme to exceptional drought conditions in the state are in northern L.A. County and parts of Ventura and Santa Barbara counties, according to the U.S. Drought Monitor.

"The drought has been so severe here that it takes a long time to replenish the groundwater system," says David L. Feldman, a UC Irvine professor of planning, policy and design. "A lot of the water runs off into the ocean."

http://www.laweekly.com/news/why-is-the-drought-not-over-yet-7903506

[Sigmetnow]

Lake Oroville nearly full from ongoing storms; normal spillway is massively eroded.

DWR: Less likely Oroville emergency spillway will be used

OROVILLE, Calif. (KCRA) —
California Department of Water Resources announced Friday that it does not anticipate needing to use the emergency spillway at Lake Oroville as water flows into the reservoir have decreased and outflows by way of the normal erosion-damaged spillway have been increased.

A team of project geologists, engineers and dam experts assessed the situation and conducted a test of the damaged Oroville Dam Spillway and decided it was the best option to release water through that as the lake was filling up.

"They knew there would still be some erosion, but it was still a usable structure and they could continue to use the spillway," DWR spokesperson Eric See said in a Friday news conference.

On Thursday evening, water officials announced that it was looking more likely that they would need to use the emergency spillway, but with inflows decreasing and outflows increasing, they pulled back on that. However, they are still preparing the area in case the emergency spillway would need to be used....

http://www.kcra.com/article/oroville-spillway-outflows-increase-as-damage-continues/8701837

[Sigmetnow]

Oroville Dam's emergency spillway used for first time amid rising waters; officials say public safe

Capping days of tense planning at the nation’s tallest dam, water flowed down an emergency spillway Saturday at the Oroville Dam for the first time after the dam’s main spillway suffered significant damage.

Water started flowing down the spillway into the Feather River early Saturday, with officials continuing to emphasize there was no imminent threat to the public or to the integrity of the dam.

The state Department of Water Resources said Lake Oroville — the linchpin of the state’s water system that sends water from the Sierra Nevada south to cities and farms — was rising to the point where water would flow down the emergency spillway. At 8 a.m., the agency said the spillway was now in operation.

Eric See, a department public information officer said it was the first time the auxiliary spillway was used to drain water from the lake since the dam opened in 1948.
...
At 770 feet high, Oroville is the tallest dam in the U.S. It was completed during the administration of Gov. Ronald Reagan and serves as the keystone for the State Water Project, which sends Northern California supplies south to the southern San Joaquin Valley and the urban Southland.

In January 1997, downstream towns were evacuated when the reservoir came within a foot of pouring down the emergency spillway into the swollen Feather River.

http://www.latimes.com/local/lanow/la-me-oroville-spillway-20170211-story.html

Brief video view: https://twitter.com/derekkcra/status/830459840229101568


Edit: State says repairs to crippled Oroville Dam could run as high as $200 million

...Throughout Saturday morning, helicopters flew back and forth over the dam area, as Pacific Gas and Electric crews worked to dismantle cables and electrical components from electrical towers on a hillside adjacent to the main spillway, concerned they, too, could be dragged into the channel below by the crashing flows.

Denny Boyles, a spokesman for PG&E, said the work was being done in “an abundance of caution” to minimize materials that might get sucked into the river if the land around the towers is eroded by the unusual flows.

Unlike the main spillway, which is lined in concrete, the emergency spillway dumps water onto a open hillside. DWR officials had worked feverishly in recent days to try to lower reservoir levels enough to avoid overtopping the emergency structure, concerned that the outflows would scour the hillside, dumping additional trees, mud and debris into the Feather River. Work crews spent Thursday and Friday removing some of the trees from the ravine below the emergency spillway as a contingency....

http://www.sacbee.com/news/local/article132154774.html