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Expect to see more emergencies like Oroville Dam in a hotter world

Posted on 20 February 2017 by dana1981

The evacuation of nearly 200,000 people near Oroville Dam is the kind of event that makes climate change personal. A co-worker of mine was forced out of his home for several days by the emergency evacuation, and another friend was visiting Lake Oroville and happened to leave 15 minutes before the evacuation order was issued.

Like many extreme events, the Oroville emergency is a combination of natural weather likely intensified by climate change. California regularly sees “atmospheric rivers” that deluge the state with rainfall, but in a hotter world, scientists anticipate that they’ll be amplified by an increase in the amount of water vapor in the atmosphere.

Northern California is in the midst of its wettest rainy season on record – twice as wet as the 20th century average, and 35% wetter than the previous record year. It proved to be almost too much for America’s tallest dam to handle. Water managers were forced to use Oroville Dam’s emergency spillway for the first time ever, which then began to erode, posing the threat of a failure and catastrophic flooding of nearby towns.


Northern California Sierra precipitation - average, previous wettest year, and 2016-2017. Illustration: California Department of Water Resources

While studies haven’t yet connected this extreme wetness to climate change (there are still several months remaining in California’s rainy season), what we’re seeing is consistent with climate scientists’ expectations of a hotter world.

Dams in the United States were built 50 years ago, on average. Since then, the Earth’s surface temperature has warmed about 0.75°C, and there’s now more than 5% more water vapor in the atmosphere as a result, which intensifies storms. With hotter temperatures, more precipitation falls as rain and less as snow, and California’s Sierra snowpack also melts earlier in the year. Climate change stresses California’s water infrastructure through all of these mechanisms.

Peter Gleick of the Pacific Institute has been researching the impact of climate change on the water cycle since the 1986, when his dissertation was the first research to conclude that the Sierra snowpack would be at risk due to rising temperatures from global warming. He also found that this would lead to increased winter runoff and flood risks, which is exactly what we’re now seeing. As Gleick told me:

Our infrastructure was designed for yesterday’s climate, not today’s or tomorrow’s. We know the climate is changing and we need to be prepared.

Gleick warned 30 years ago that this increased runoff would add stress to California’s water infrastructure, also noting that in a hotter world, more precipitation would fall as rain and less as snow.

California will get the worst of all possible worlds – more flooding in the winter, less available water in the summer.

Gleick’s words now seem prescient. Research has shown that conditions that create both wet years and hot dry years in California are becoming more frequent. California’s intensely wet 2017 is a prime example of weather whiplash, as the state is just now emerging from a 5-year drought that was its most intense in more than 1200 years

Studies have found that global warming intensified that drought by about 15–35% through factors like increased evaporation and water demand, pushing it into the realm of record-shattering intensity. As Gleick recently wrote, extreme weather is battering California:

We already see fundamental changes in storm frequency and intensity, increases in the size and duration of droughts and rainfall events, disappearing snow packs, growing agricultural water demands with rising temperatures, and more.

We cannot afford the luxury of pretending climate change isn’t real, and we cannot afford to ignore the risks to our water infrastructure posed by these changes. Any investment in infrastructure must take climate change into account through smart flexible design, integration of better weather-forecasting and modeling tools, and adoption of new standards for facility construction and operation.

Environmental groups warned the state about Oroville Dam in 2005, noting that in an intensely wet year like we’ve seen in 2017, its emergency spillway could erode, and thus should be coated with concrete. State agencies concluded that the cost of this project couldn’t be justified given the low probability of such a wet season, but climate change increases the likelihood and intensity of extreme precipitation events. The environmental groups were proven right.

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Comments 1 to 9:

  1. The emergency spillway had to be used because the main spillway failed and then had to be put back into service because of the imminent catastrophic failure of the emergency spillway.    It is likely that if the main spillway had not been damaged the level of the lake could have been lowered without using the emergency spillway and therefore evacuations would not have been required. Is this a road we really want to go down where everything is attributed to CAGW?

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  2. Jipspagoda,

    Do you really want to not tell people that a large part of the problem is caused by AGW?  Even if AGW is only responsible for 20% of the precipitation, the flooding would not have happened without that contribution.  The main spillway is reported to have failed due to erosion from the heavy rains so it has the same ultimate cause.  If it was not warmer due to AGW the rain would have been snow and they would not have had any problem.   Can you suggest a situation where this flooding would have occured without AGW?  It would be extremely unlikey.

    All weather is affected by AGW.  Whenever there is record damage from weather it is always worse because of AGW.  People need to be reminded every time.  Most people in the USA do not really remember when Pakistan or Bangladesh is flooded.  They notice California a lot more.

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  3.  MS, 

    Extreme droughts and floods have happened in the past and  will happen in the future.  Seems more like failure to plan for the past and the future to me

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  4. The issue is that GW increases the frequency of major rainfall events and thus the risk, something the environmental groups challenging the spillway safety 12 years were well aware of.

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  5. The main spillway failed due to unprecedented volumes of water cascading down its length.  Where did all that water come from?  1) falling as rain rather than snow (AGW), 2) unprecedented amounts of rain (AGW), 3) falling on hillsides denuded by five years of unprecedented drought (AGW).  I'm not surprised that infrastructure like this is taxed past its design limit by the unprecedented conditions that have long been associated with AGW.  It's part of a pattern, as the author states "what we’re seeing is consistent with climate scientists’ expectations of a hotter world."  Munich Re recently reported that severe flood events in Europe have doubled since 1980.  So it would be folly to not ready our infrastructure for more of this: the point of this article.  

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  6. Situation in CA is identical to "inland tsunami" fluds in QLD 6 years ago. After a decade of misarable drought, the freak and very intense rains filled Wivenhoe Dam to some 170% of its capacity. The dam operators must have spilled signifficant amount of water, otherwise it may not have held. Everyone was quick to blame dam operators (ditto as jipspagoda@1,3 above) but refused to acknowledge the unprecedented weather event (weather on steroids is avery accurate term here) leading to the tragedy; and at the same time tried to dismiss any links to AGW with "weather has always been unpredictable" trolls (exactly as jipspagoda@1,3 above). Give me a break, deniers: how many times do we need to repeat the obvious that AGW signal is responsible for increasing magnitude of extreme precipitation events like this one in CA and recent one in QLD? You can argue that the dam operators could have better handled the emegrencies (if they could have predicted the magnitude of these emergencies 50y ago) but do not dismiss the obvious influnce of AGW signal here, as proven by climate scientists and the long term weather data.

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  7. Jipspagoda,

    It is common knowledge that there are large rains in the American West on 100-200 year intervals.  California and the feds decided that it was not worth ,spending the money for an event that has not happened since 1862.  As pointed out above, AGW made the flood worse.  It is very unlikely that with natural forces alone that Oroville dam would have neared faliure this year.  AGW added the extra to force failure.

    They are expecting 10 inches (25 cm) of rain at Oroville this week from a new storm.  Other reservoirs are full and there will be significant flooding.  Oroville expects to be low enough to slow the flood as long as the damaged main spillway holds out.  The rainy season is nearing its end.  How much water will fall in March?

    What Ubrew12 said x2.

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  8. The likely reasons for the Oroville Dam's main spillway failure are identified and explained in:

    Damage to Oroville's main spillway 'was an accident waiting to happen' by Ralph Vartabedian, Los Angeles Times, Feb 20, 2017

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  9. jipspagoda:

    The Earth can be compared to a bed that has had an extra top sheet added. Whether it is a cold night or hot, the occupant will be slightly warmer. That translates as a more energetic atmosphere, where every event has an element of AGW, mostly small but sometimes large or even contradictory, like the massive snow dumps. The larger events are likely to exceed the capacity of our infrastructures, topping stopbanks, depleting water resources, overloading air conditioners. And if we don't pull finger and deal with our excessive release of "thermal blanket" (greenhouse gases) the situation will only get much, much worse.

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