Oroville Dam: Crisis Eases, Emergency Spillway Repairs in Progress

February 15th, 2017 by Roy W. Spencer, Ph. D.

With the evacuation order lifted last evening, and ~185,000 residents returning to their homes in Oroville and surrounding communities, emergency repairs continue around the clock on the damaged emergency spillway at Oroville Dam. Yesterday morning (Feb. 14), a concrete pumper and boulders were being used to patch the main erosion features that developed when the emergency spillway was overtopped:

The water level of the lake is being reduced by 8 or 9 feet per day, and now stands at 880 ft., which is 21 feet below the top of the 901 ft.-elevation concrete weir that was overtopped a few days ago by 1.5 ft. The rapid lowering of the lake is being accomplished with a continuous 100,000 CFS flow over the main spillway (the same as the average flow over Niagara Falls) which was heavily damaged over a week ago:

Little more than one day of only about 10,000 CFS flow over the concrete weir of the emergency spillway caused unexpected erosion down into the highly fractured bedrock, which is what led to the evacuation orders as the continuing erosion back to the concrete weir led to fears that structure could be compromised:

I’ve been following a continuing discussion by outside experts here, and also following the forecasts of a series of new storms that will sweep through California over the next week.

Based upon everything I’ve seen, I’d say that for the foreseeable future, the dam facility is out of danger. Here’s why:

1) The 100,000 CFS flow through the (damaged) main spillway will, in all likelihood, keep the lake level below the 901 ft. elevation of the emergency spillway. Even though the next week of storms will cause as much as 7-14 inches of liquid-equivalent precipitation to fall, much of that will fall as snow except over a relatively small portion of the watershed. The 100,000 CFS flow rate through the main spillway could be increased to 150,000 CFS if needed.

2) As of yesterday, the main spillway damage was not eroding uphill, suggesting that portion is on bedrock. It is possible that the remaining concrete is actually more stable at higher flow rates, which creates a waterfall out and away from the bedrock the concrete flume is sitting on.

3) Spring snow melt usually occurs slowly enough that the main spillway will be able to keep up with it.

4) Even if the concrete weir is over-topped again, and erosion of the bedrock extends back to the concrete weir, that structure is very thick, and it is not at all obvious that it would fail. This is a big uncertainty, though, and if it ever gets to that point, evacuations would again be announced.

Note that all of this positive outcome depends upon the undamaged uphill portion of the main spillway remaining stable. This is why repairs to the hillside below the emergency spillway are being performed as fast as possible, in case the main spillway fails and the lake level rises uncontrollably, and then once again overtops the emergency spillway weir.

I believe that the use of the previously-untested emergency spillway, and the resulting damage, was actually a blessing in disguise. That structure was designed to handle 10-15 feet of water flowing over it, but it only took 1.6 ft of flow to cause substantial hillside erosion in less than 2 days. Now that the geology of that hillside has been revealed, engineers will be able to come up with an engineering solution so that if there ever is a catastrophic flooding event, the emergency spillway will be in a much better state to handle it without failure of the concrete weir, which could result in a ~30 ft. wall of water to cascade downstream.

124 Responses to “Oroville Dam: Crisis Eases, Emergency Spillway Repairs in Progress”

Toggle Trackbacks

  1. Steve Case says:

    Dr. Spencer, thank you for your excellent reporting on this topic. The so-called mainstream media is nowhere near as objective or forth coming with the “What you need to know” information about the Oroville Dam over the last two weeks.

  2. Ken in Idaho says:

    Dr. Spencer,

    Another thank you for the reporting and the links to other information on this topic. I have a younger brother studying Geology now and this was an example of why the world needs geologists.

    I also thank you for the perfect case study of why experts in one field should stick to making important decisions in their field and not extending expert status into another. Hopefully some physicists , chemists and lawyers can stop butting into climate science.

    • michael hart says:

      “Hopefully some physicists , chemists and lawyers can stop butting into climate science.”

      That will happen the day climate scientists stop butting into economics and world governance.

      For crying out loud…

      • michael hart says:

        …and since when did so-called “climate science” not depend on Mathematics, Physics, Chemistry, and Biology? And forbid criticism from such discipline?s

        It is a jack-of-all-trades science. Richard Lindzen has expressed his professional observation that it attracts “B-grade” students who simply couldn’t hack it in the traditional hard sciences.

        I don’t think that is true for all of them, but a substantial fraction come at it from the standpoint of “I wanna save the world, but I’m not sure how. So I’ll go into a “science” which entails telling people what to do in every other occupation under the sun”. This was formerly known as politics. Their interests in real science are actually very small.

        For an analogy, I wanted to go into Medicinal Chemistry because the science of, say, cancer treatments, excited me. I did not go into Medicinal Chemistry because I wanted to tell people to stop smoking. Can you see the difference?

        • Gordon Robertson says:

          michael hart…”a substantial fraction come at it from the standpoint of I wanna save the world, but Im not sure how. So Ill go into a science which entails telling people what to do in every other occupation under the sun”.

          I think there’s truth in what you say. Many people come to science pre-conditioned to see science in a certain way and nothing is done to de-condition that type of thinking. In fact, the opposite is often true. Universities are prone to established paradigms and have no interested in ensuring that students learn to observe reality without a conditioned bias.

          For example when I studied physics courses as part of an engineering program, our physics text books gave no definition of time, nor did they distinguish between man-made parameters like temperature, density, linear measure, and so on. In other words, I was expected to fully accept definitions without question.

          You won’t see an attempt to define basic parameters in most texts and I was lucky enough to find a reference by Max Planck in his book on heat in which he made it clear that parameters like time, pressure, temperature, and linear measure were developed by humans for convenience in measurement.

          The phenomenon of momentum is real but the definition of momentum by humans, basically mass x velocity, falls apart with the definition of a photon having momentum but no mass. Obviously, a photon is a definition as well and Einstein was never convinced that light consisted of photons rather than as a wave front.

          It was not till years after university that I began to challenge the meaning of time and that was based on dialogs between the physicist David Bohm and Jiddu Krishnamurti. They both delved deeply into the relationship between time and thought and it became glaringly apparent that time as the past is nothing more than thoughts stored in human memory in a linear order.

          Past and future are nothing more than stored thoughts and there is no time arrow in existence as claimed by many scientists.

          Of course, we developed measuring devices called clocks that can measure the period of rotation of the Earth and we can subdivide that period into a basic measure we define as a second. We can use the second to keep tract of change but we need to understand that the time generated is nothing more than an illusion stored in human minds. No other species sees time as we humans do or cares about it.

          Still, I wasn’t sure till one day I bumped into a physics prof who had taught me physics at university. I ran my idea past him that time did not exist and he agreed. He told me that time was invented by humans to keep tract of change.

          In light of that, space-time curvature becomes a bad joke. It can exist as an illusion in the human mind but I saw an astronomer doing a TV presentation claim that gravity is not a force but a warp in space-time.

          Good grief, they are teaching that rot to students in university. Can you imagine what they are teaching in climate science and related fields?

        • David Appell says:

          Gordon Robertson wrote:
          “I ran my idea past him that time did not exist and he agreed. He told me that time was invented by humans to keep tract of change.”

          Absurd. What do you think happened between when you read THIS word and when you read THIS one??

          “In light of that, space-time curvature becomes a bad joke. It can exist as an illusion in the human mind but I saw an astronomer doing a TV presentation claim that gravity is not a force but a warp in space-time.”

          Wrong — spacetime’s curvatue can be measured. See Eddington, solar eclipse, starlight deflection, 1919.

          Gravity is BOTH a force AND a curvature in spacetime. (No hyphen, by the way.) The two views are equivalent. That was Einstein’s big accomplishment. Though I would never expect an engineer to understand that.

      • David Appell says:

        Climate science is applied physics. It needs physicists. And other specialities too.

        A professor from my undergraduate days said that physicists proved their worth in WW2, particularly when Fermi impressively estimated the Alamogordo bomb yield by dropping little pieces of paper from his outstretched hand.

        • Gordon Robertson says:

          DA…”Climate science is applied physics”.

          You are confusing climate science with engineering. Engineers take physics principles and apply them to building bridges, dams, buildings, aircraft and so on. From what I have seen, some climate scientists, but not all, misinterpret physics.

          I would say John Christy of UAH is a good climate scientist because he recognizes the complexity of the atmosphere and how difficult it can be to apply physics to the atmosphere. However, I regard his mentor as a grad student, Kevin Trenberth, to be a questionable climate scientist due to his politics and alarmist tendencies.

          Trenberth has interfered in peer review and in the Climategate email scandal, his Coordinating Lead Author partner on IPCC reviews, Phil Jones, threatened that he and ‘Kevin’ would see to it that certain papers would not make it into the IPCC peer review process. One of those papers was by John Christy.

          I take my hat off to John Christy (along with Roy Spencer) for having the guts to examine the NOAA satellite temperature data and give the honest appraisal that little or no ‘true’ warming has occurred during the 35 years of the NOAA sat record.

          To stand up to a heavy weight like Trenberth, along with the entire climate science community, takes integrity and guts. Too bad most of the rest of them lack those qualities.

          • David Appell says:

            No, I’m not.

            Engineers take physics — quite basic physics, in fact — and apply it.

            It takes much more than that to understand quantum mechanics and radiative transfer. I doubt any engineers ever do. Engineers simply can not and could never do the necessary calculations.

            I gather, Gordon, that you are/were an engineer. Your many many errors here, many simple and basic, demonstrate what I just wrote.

          • David Appell says:

            Gordon Richardson wrote:
            “Trenberth has interfered in peer review and in the Climategate email scandal, his Coordinating Lead Author partner on IPCC reviews, Phil Jones, threatened that he and Kevin would see to it that certain papers would not make it into the IPCC peer review process. One of those papers was by John Christy.”

            Prove it.

            Just once, prove something you claimed.

            You never do. Because you clearly can’t.

            So prove this.

        • David Appell says:

          Gordon wrote:
          “I take my hat off to John Christy (along with Roy Spencer) for having the guts to examine the NOAA satellite temperature data and give the honest appraisal that little or no true warming has occurred during the 35 years of the NOAA sat record.”

          Time and again you prove you understand almost nothing.

          When I started college I thought I wanted to major in electrical engineering. But the intro to engineering class was very formulaic, only about plugging numbers into formulas than understanding where the formulas came from. My fellow students were mostly interested in how much money they would make upon graduation.

          During the semester break I read Ronald W. Clark’s biography of Einstein. He wrote about people passionate about ideas, and not about money. He wrote about how Einstein and others of the time were motivated to understand the world, and not about what paychecks they would receive.

          When I went back to the next semester I changed my major to physics. It was one of the best decisions I ever made I ever made in my life.

          • Gordon Robertson says:

            DA…”Time and again you prove you understand almost nothing”.

            And time and again you prove what a trolling idiot you are. Your response, indicating that you could not hack the tremendous work load required in engineering, including an honours physics level of study, settling for an easier route in physics, suggests you do take the easy way out.

            Please don’t smear the excellent reputations of John Christy and Roy Spencer with your lame personal background. As a student in physics you demonstrate a complete lack of ability to understand the atmosphere. The fact that you think a trace amount of CO2 can cause catastrophic warming and climate change proves you learned nothing in physics.

            You are a follower. You don’t have what it takes to be a skeptic.

          • David Appell says:

            Work load? I doubled majored, in mathematics and in physics, with honors. Then got the next two higher degrees in physics. Then worked at Bell Labs. Then had the balls to drop out and do something that mattered to me.

            So I’m not very impressed by engineers, and even less by you. Many engineers — not all — are like you, thinking they know everything while showing all along the way that they can’t do more than plug numbers into formulas and have no grasp of the fundamentals.

          • David Appell says:

            Gordon Robertson says:
            “Please dont smear the excellent reputations of John Christy and Roy Spencer with your lame personal background.”

            I wasn’t insulting them, Gordon, I was insulting you.

            Please try to keep up.

          • Nate says:


            It seems to me that you have a political (or perhaps religious) agenda above all else. Why else do you seem to you care so little for scientific facts, logic, and scientific arguments, as you continually deny them or avoid them like the plague. Instead you continually return to your ‘alternative facts’ that have been debunked repeatedly, like a broken record.

          • AndyG55 says:

            Rotten Appell lasted only 5 years in actual work, 4 jobs.

            A monumental FAILURE.

            Then he found something he could actually do, low-end science fantasy for garbage magazine.

            And he’s a failure at that too.

          • AndyG55 says:

            I wonder how many class-mates had to help rotten appell get through those subjects, because he has proven over and over again that he lack basic understanding in essentially everything. He is a mathematical non-entity, with very little real idea what he is doing, and his grasp on physics is tenuous to say the least.

          • C Morris says:

            You show you have no understanding of what it takes to be an engineer, and your denigrating tone sums up why engineers hold people like you in contempt. Coming out of university with an engineering degree only makes you a graduate. Then you have to learn how to put the theories into practice. That is why many don’t become professional engineers until well into their 30s and many don’t even do that.
            Engineers have to make real time decisions that they need to get right – if they are wrong, people die. That is a big difference between us (I’m a power station engineer) and your idols. Because of the nature of my job, I do a fair bit of work with both scientists and academics (and to satisfy your snobbery, I have authorship of a page of peer reviewed papers in my CV)and I spend a lot of my time having to explain to them exactly how things work. We might not understand the theory of quantum mechanics or radiative transfer, but we know a lot about subjects like fracture mechanics and cavitation, especially the practical side. And we understand the implications and limitations of the laws of thermodynamics.
            Reading your rants reminds me a lot of the Pope poem about “a little learning is a dangerous thing” though not many people know the punchline, let alone understand it.

  3. Curious George says:

    Thank you for a nice summary. The engineering aspect seems to be under control, but the political elite will find something else to mess up.

    • Never let a good crisis go to waste.

    • David Appell says:

      Curious George says:
      “The engineering aspect seems to be under control, but the political elite will find something else to mess up.”

      The “political elite” saved this dam and prevented a major catastrophe. Does that count for nothing?

      • Lewis says:

        The “political elite” did nothing to save this dam. They, when involved, were only concerned about themselves. Those who made the decisions, whatever they were, were much removed from elite status. Also, those who made the decisions would also be those whose heads would drop if things went south.

        The elites protect their own, not others.

        • David Appell says:

          The dam officials prevented a catastrophe, and made the right decisions that keep people safe.

          Curmudgeons like you would never give credit to any of them — you’re too angry at the world, and root for failures in the hope of confirming your rotten attitude.

          What do we say to death? Not today!

          • Lewis says:

            Dam officials are hardly political elite. I give them all the credit they deserve. They made the only decision they could. Hardly worthy of great accolades. They had 3 choices. Keep running water over the emergency spillway. Dump water, as they did, from the regular spillway, or wring their hands.

            Again, hardly worthy of accolades – they didn’t have any choices.

            Angry at the world, hardly. Just honest about how people operate.

            Take you for instance. You regularly read things into what people write, avoiding reading for comprehension and instead imagining something that is not there.

            So let me be clear. If they were elite, they wouldn’t be working at the dam and neither would they be held responsible if something went south. That is for lower level bureaucrats.

      • barry says:

        The political elite seem to have been unhelpful in the past. A $100 million upgrade proposal by locals was rejected by the feds in 2005.

  4. Mark Ping says:

    We’ve been following it pretty darn closely here in Chico (fun fact, the main spillway can discharge water with the level as low as 813 ft). I’d say you got everything right here.

    It’s a bit frustrating that the strategy of not paying for infrastructure fixes appears to have worked. It appears we’re getting fed money so our nutty governor can play with his choo choo priority.

    The good news is that the multiple billion-dollar bonds we’ve funded to increase our water storage might actually get used correctly now.

  5. Tim S says:


    I have been following the discussion of suction on the other site in your link. I believe that a full vacuum down to the vapor pressure of the water is possible on the spillway. It is this simple:
    The sides of the spillway contain the water. If the horizontal component of the velocity of the water in the spillway is high enough to exceed the rate at which gravity allows it to fall, relative to the increasing slope of the spillway, it could separate from the spillway. Waterfalls often do this at the top. The difference here is that the walls contain the water so that air cannot enter from the side, and thus a vacuum will form as the water separates from the spillway floor causing the water to boil at its vapor pressure.

    • Roy Spencer says:

      OK, that’s a better explanation than that given by “Ralph” at that site. I’ve never heard of this before, but your explanation makes sense…at least the part there water flow down an increasing slope could exert an upward force. (I don’t know whether actual “cavitation”-type feature would occur). A quick Google search didn’t give me anything, but I’m sure this possibility has to have been addressed before. I’d be curious what’s out there on the subject.

      • Tim S says:

        Yes, this would be a cavitation effect where the liquid boils as the pressure is relieved. Cavitation can occur in pumps if the inlet is restricted and throttling valves if there is a large pressure drop across the valve leading to high velocity. As for the spillway, it is possible that it was designed for a certain flow, and exceeding that flow causes this effect, which the original designers were aware of but accepted because the high flow would be brief only a long term problem. If so, they were wrong.

        • Mike M. says:

          Tim S,

          If the flow were to separate from the spillway surface, wouldn’t violent turbulence result? That would lead to the sort of behavior that is now seen at the point where the spillway is damaged. Water would no longer be confined to the spillway and the turbulence would likely cause great damage to the spillway. The engineers who designed the spillway would have been careful to avoid that.

          I think that the spillway was designed for a maximum flow of 290,000 cfs and has never carried more than 160,000 cfs. So flow separation/cavitation should not have occurred unless the spillway was damaged. But once the spillway was damaged, those effects would have rapidly increased the damage, which is what seems to have happened.

          • lokenbr says:

            Mike M. you beat me to it – I did not see your reply when I sent mine. Your reply is much more thorough 🙂

          • Tim S says:

            I tend to agree. My analysis is hypothetical. The most likely explanation is that there were cracks in the concrete that disrupted the flow. If the crack is wide enough for flow to get under the concrete slab, it could create enough erosion of the underlying surface to eventually lift the slab or cause it to settle. This could be a very rapid process if the bottom edge of a slab starts to settle and cause the water to impact the uphill face of the slab below.

      • lokenbr says:

        Cavitation would be a common design issue on steep spillways I should think. Roughness due to irregularities in the channel could also initiate local cavitation.

      • Robert Stewart says:

        Cavitation has been a major problem in submerged spillways like that at the Glen Canyon Dam in 1983, and the Yellowtail Dam on Montana’s Big Horn River in 1967. The operators of the Yellowtail Dam discovered that injecting air into the flow allowed them to eliminate the cavitation damage. Unfortunately, the Glen Canyon operators did not upgrade their spillways before they suffered very serious, even dam-threatening, damage. My reading suggests that air injection is now a standard feature of submerged spillways.

        The free surface spillway at Lake Oroville is obviously very turbulent as it emerges from the control gates, and must entrain a lot of air. The videos make it appear as though it is frothing, but I haven’t seen any close up views of the flow. This leads me to think that cavitation is not a major issue in the present crisis. I would be more concerned about the undermining of the spillway slabs, or the potential for battering of the spillway surface by any debris from the dam that might be discharged in the outflow.

    • Lasse says:

      Good statement Tim S!
      Cavitation may destroy the concrete. Air can also act as a lubricant to make the friction less destructive.

  6. ossqss says:

    I wonder if they can inject mortar/concrete into the fractured bedrock. Similar to how they address sinking foundations or sinkholes in some areas.

  7. Fulco says:

    Did I see it right ?

    Is the parking lot a weak spot in the dam. It seems like soil is washed away beneath it. They are plugging a hole next to the parking lot.

    • Actually, the concrete weir extends all the way to that repair point. It’s mostly hidden underground. The bedrock it sits on slopes upward to that point.

      • Fulco says:

        So water can sip between the weir and the bedrock.
        How can it otherwise wash soil away from beneath the parking lot.
        They have also registered small earthquakes on that side of the dam.
        Does not sound good.

  8. Mike S says:

    Just a reminder that weather prediction is not an exact science.

    The 7 day total QPF forecast from the National Weather Prediction Center for the Oroville Dam basin continues to increase. Highest prediction is now at 14.5″. Although it needs to be considered how much ends up as snow (which would mitigate substantially the runoff)


  9. Tim S says:

    There is another issue that is not as dramatic, but possibly just as destructive, and that is downstream flooding. Shasta is the largest reservoir in the state. It is currently at 93% capacity and releasing 74,000 cfs. A few days ago it was at 97% full. The confluence of the Feather River and Sacramento River (Shasta release) is above Sacramento. There are various levee system all the way to San Francisco Bay that are vulnerable. There already is flooding in the delta region at the confluence of the Sacramento River and San Joaquin River, which is the drainage for numerous rivers in the southern Sierra Nevada mountains and the Central Valley.

  10. ossqss says:

    Interesting perspective of the erosion in this picture. It appears to be just below a raised area on the spillway bottom. I would assume the water flow in that area would be more disruptive and perhaps added to the decay immeadiately below. Same seems to be happening below the larger arched area to the right. Just a thought from a novice.


    Borrowed from Jonova’s site.

  11. CO2isLife says:

    It would be interesting to see the California budget for repairing dams and compare it to what they spend on “green” issues.

    Just How Much Does 1 Degree C Cost?

  12. AaronS says:

    I am all for hydroelectric power and damns. However, it amazes me how 11 deaths and a discharge of only 2x the natural annual seepage amount of oil in Gulf of Mexico is a media catastrophe, but damns are considered low risk. In 1975 in China damn failure showed hydro is the highest risk source of energy and it is not alone. Perception is amazing vs reality. Same with fear of modern nuclear.


    • Burrado says:

      I’m thinking the same – that who would want to do away with such an amazing and “free” source of energy. Yet, I had no idea there was such huge loss of life. Eye-opening to say the least. Also amazing how many of the catastrophes were a result of heavy rain. I would still think that dams could be almost failure proof provided people were willing to pay for as much redundancy and overbuild as necessary to go that far.

      • David Appell says:

        Heavy rains are increasing with AGW.

        • Lewis says:

          Perhaps you prefer drought?

        • Gordon Robertson says:

          DA…”Heavy rains are increasing with AGW”.


          • David Appell says:

            Read the IPCC SREX and learn something for a change.

            I dare you.

          • C Morris says:

            David, rather than tell us what unverified models tell us about rainfall, how about giving us data showing both extreme rainfalls and droughts are increasing?

          • David Appell says:

            Read the IPCC SREX.

          • David Appell says:

            :There have been statistically significant trends in the number of heavy precipitation events in some regions. It is likely
            that more of these regions have experienced increases than decreases, although there are strong regional and
            subregional variations in these trends. [3.3.2]”

            – IPCC SREX SPM p6


          • Norman says:

            Mike M.

            You beat me to the research. I was going to post this link for David to review.


            Quote from conclusion: “Analysis of the global land area with annual PMPE less than zero for the 1901 through 2009 period indicates that %drought has not changed, even though global T and PET have increased during this period.”

            I would suggest David Appell read the latest issue of Scientific American. In the Article about Inflation Theory titled “POP goes the universe” refer to the last segment titled NONEMPRICAL SCIENCE.

          • C Morris says:


            As I thought, you have nothing beyond your mantra of the SREX being the good book. it is well known that the document was heavily massaged and in many places, contradicted the WG1 information. As a contrast, the TS says:
            “It is likely that since 1950 the number of heavy precipitation events over land has increased in more regions than it has decreased. Regional trends vary but confidence is high for North America with very likely trends towards heavier precipitation events. {2.6.2; Table 2.13}

            There is low confidence in a global-scale observed trend in drought or dryness (lack of rainfall), due to lack of direct observations, dependencies of inferred trends on the index choice and geographical inconsistencies in the trends. However this masks important regional changes and, for example, the frequency and intensity of drought has likely increased in the Mediterranean and West Africa and likely decreased in Central North America and North-West Australia since 1950. {2.6.2; Table 2.13}

            During the last millennium, there is high confidence for the occurrence of droughts of greater magnitude and longer duration than observed since 1900 in many regions. There is medium confidence that more megadroughts occurred in monsoon Asia and wetter conditions prevailed in arid Central Asia and the South American monsoon region during the Little Ice Age (14501850) compared to the Medieval Climate Anomaly (9501250). {5.5.4, 5.5.5}

            Confidence remains low for long-term (centennial) changes in tropical cyclone activity, after accounting for past changes in observing capabilities. However since the 1970s, it is virtually certain that the frequency and intensity of storms in the North Atlantic has increased although the reasons for this increase are debated (see TFE.9). There is low confidence of large-scale trends in storminess over the last century and there is still insufficient evidence to determine whether robust trends exist in small-scale severe weather events such as hail or thunder storms. {2.6.2, 2.6.3, 2.6.4}

            With high confidence, past floods larger than recorded since the 20th century occurred during the past five centuries in northern and central Europe, the western Mediterranean region, and eastern Asia. There is medium confidence that in the Near East, India, central North America, modern large floods are comparable or surpass historical floods in magnitude and/or frequency. {5.5.5}”

            Note that they only discuss what has happened to rainfall since 1950, though rainfall records for the US go back a century before then. As others have pointed out, the full data record doesn’t support the cherry picked trend.

            So how about you actually ready something.

          • C Morris says:


            This paper extends rainfall records back to mid 1700s, at least for Southern California.
            As per usual, your armwaving and snide statements aren’t supported by the evidence.

          • Gordon Robertson says:

            DA…”Read the IPCC SREX and learn something for a change”.

            Why are you citing the IPCC when you completely ignore their 2013 revelation from AR5 that no significant warming has occurred in the 15 year period from 1998 – 2012? And why do you negate them with a study from NOAA that was rushed out for Obama at the Paris climate talks?

            I don’t read the IPCC for several reasons:

            1)they admitted in TAR (2001) that future climate states cannot be predicted then they went ahead and ‘projected’ future climate states based on unvalidated models.

            2)they have devised a system to evaluate opinion. For example, a ‘likely’ means they have a confidence in the opinion greater than 65%. The article to which you link says ‘likely’. There is little or no meaning to their ratings.

            3)their lead authors are politically selected and they appoint reviewers. When the review is complete and the reviewers supply a main report, 50 politically appointed lead authors produce the Summary for Policymakers and amends the main report to reflect the views of the 50.

            4)their process is essentially corrupt.


            Look for hyperlinks in each category.

        • AndyG55 says:

          “Heavy rains are increasing with AGW.”

          RUBBISH !!

  13. Norman says:

    Pray that the repairs worked and the upcoming rain causes no further evacuations. I sympathize with the people who are told to evacuate in a hurry and leave all behind hoping for the best. Human ingenuity when under pressure can be an amazing thing. Hope it comes out on top for this Dam.

  14. Hkan says:

    What is the problem with the main spillway? Does the damage limit the flow?

    • Robert Stewart says:

      The flow is limited by the operators who control the eight gates at the top of the spillway. They have limited the flow out of sense of caution. They believe that at the 100,000 cfs flow rate, the hole will remain somewhat stable. The fear is that it could undermine the material beneath the spillway just above the hole, and this would lead to the collapse of another section of the spillway. And if that happened, they’d have to give serious thought to continued growth of the hole. So far, at the present discharge, they haven’t seen that. So perhaps the hole will not grow. It’s a heck of a way to run a railroad, but that’s where we’re at.

      • Roy Spencer says:

        They backed off on the flow because the lake level is low enough that the intake to the spillway will cause considerable erosion, due to faster water speed over a lesser depth at the spillway entrance.

  15. ren says:

    In a few hours it will be the first attempt to Sacramento. Rain will come from the south.

  16. Lasse says:

    Excellent text and good work from the civil engineers and constructors.
    When a problem is occurring in a good construction there is always ways to fix it.
    Nature is hard to manage at extremes but when time is on our side many things can bee done. I guess You will see injection of concrete at the sit for a long time.
    It is also interesting to observe spillway in operation after haven taken a class at Berkeley in spillway design 😉

  17. Lewis says:

    To Eric – From Previous blog.

    Thank you. The reason I had asked was I had run a 1.5″ pipe from a creek across a ridge to a pond. It worked fine until I moved it to a shorter route across the top of the hill, then… I guessed it was boiling the water at low pressure, but you have verified that is what happened. I moved it back to the longer, lower route and it works fine.

    15 gals per minute keeps the pond full.

    • Eric says:

      Cool. Another way to look at it, is atmospheric pressure can only push the water up to 32′. Above that point, the downward pressure of gravity (from the weight of the water in the column) exceeds the upward pressure from the atmosphere. In the case of a siphon, above that height, the water vapor (from the boiling water) will create a break (or gap) in the water column, and thus the siphon fails.

      • Gordon Robertson says:

        Eric…”…atmospheric pressure can only push the water up to 32′…”

        Not sure about that, seems to me it’s a bit more complex. There’s a difference between gas pressure, which is the average kinetic energy of gas molecules acting on a container surface, and atmospheric pressure, which is the effect of gravity on atmospheric gases.

        I looked it up for reference even though my studies in engineering suggested it was gravity causing the flow in a siphon not atmospheric pressure. My reasoning was that a siphon has to be primed by sucking fluid through it first. Seems the atmospheric effect has been perpetuated by dictionaries for more than a century. The Oxford dictionary recently offered to change the explanation.


        Gas pressure, of course, depends on the gas density and in the atmosphere, that density is a maximum at the surface due to the gravitational force acting on air molecules. Gravitational force varies in the atmosphere, getting strongest near the surface.

        Gravity causes the 32′ limit to which you refer above, not atmospheric pressure. Atmospheric pressure is not enough to push water 32 feet up a pipe. In fact, gravity causes atmospheric pressure due to progressively increasing the density of the gas molecules in the atmosphere.

        If you hung a siphon pipe over the edge of a dam to lower it’s level it would not automatically start draining the dam. Atmospheric pressure on the water in the dam could not push the water up the pipe on its own. You’d have to prime it by sucking water down the pipe first. Then, the force of gravity on the water inside the pipe would ‘suck’ water out of the dam.

        If you have ever tried sucking gas out of a gas tank using a siphon hose, you know you can’t just hang the tube in the gas tank and expect gas to run out. You have to prime it first by sucking the gas till it flows, usually getting a mouthful of gas in the process. Once the flow starts gravity will act on the downside part of the hose liquid to suck gas out of the tank.

        In my mind, a siphon is not that practical when you have powerful immersion pumps that will sit under the water surface and pump the water out of the dam through a hose at a much higher rate than a straight siphon.

        The 32 feet to which you refer comes from the accelerating force of gravity which accelerates objects at 32 feet/second/second. I’m, not clear on this but I’m sure the limiting factor with how high the water will rise in a pipe is related to the gravitational acceleration constant which is 32 feet/sec^2 or 9.8 metres/sec^2.

        • Tim S says:

          This is either poorly written, or you don’t get. For ice cold water at sea level, it is closer to 34′ (33.8). The limitation in a siphon is the temperature of the water affecting its boiling point combined with the available atmospheric pressure. You are correct that gravity is pulling the water out of the discharge end, but the ability to prevent flashing in the top of the pipe depends on the vapor pressure of the liquid. When the liquid boils, the siphon is broken. The available atmospheric pressure determines the height at which the pressure becomes low enough for boiling to occur.

          • Gordon Robertson says:

            Tim S…”When the liquid boils, the siphon is broken”.

            I have to post this in two sections at least. Roy’s system does not like certain words.

            Well, yeah. Boiling will break the molecular cohesion that allow water molecules to adhere to each other.

            There is a misconception, however, that atmospheric pressure on the water surface is forcing water up the intake pipe, which is incorrect. That could be tested quite easily by placing a clear tube in water to see how high the water will rise in the pipe. I’m willing to bet it won’t rise perceptibly.

            In fact, I just did it. I stuck a half inch I/D clear tube in a tub of water and the water did not rise in the tube at all, as far as I could see.

            Also, the fact that a siphon will not work without suction being applied to the discharge end proves that atmospheric pressure on it’s own cannot drive water up the intake pipe.

          • Gordon Robertson says:

            Tim S and nate…

            It’s explained well at the following link although it’s all done in a lab with narrow gauge siphon tubing:


            “The maximum height of a siphon is generally assumed to be dependent on barometric pressureabout 10?m at sea level. This limit arises because the pressure in a siphon above the upper reservoir level is below the ambient pressure, and when the height of a siphon approaches 10?m, the pressure at the crown of the siphon falls below the vapour pressure of water causing water to boil breaking the column. After breaking, the columns on either side are supported by differential pressure between ambient and the low-pressure region at the top of the siphon. Here we report an experiment of a siphon operating at sea level at a height of 15?m, well above 10?m. Prior degassing of the water prevented cavitation. This experiment provides conclusive evidence that siphons operate through gravity and molecular cohesion”.

            Note that 10 m is about 32.8 feet. I was wrong with my reasoning based on gravity accelerating masses at 32 feet/sec^2 but correct, according to the article, that a siphon works due to gravitational force and molecular cohesion.

          • Eric says:

            Thank you Tim. For those that don’t think atmospheric pressure and gravity control the max height of the column, remember this: Fluids move from higher pressure to lower until equilibrium is reached. Atmospheric pressure and gravity reach equilibrium in a (closed at the top) column at 32 feet (for water). Yes, the water boils at the surface, but even without boiling, you could never lift water above 32 feet by providing a vacuum at the top and atmospheric pressure at the bottom. Secondly, watch what happens when you change the pressure above the water. Try to “suck” water up a column from a sealed tank. Can’t be done, because there is no atmospheric pressure to “push” the water to lower pressure. Next, consider adding air to a sealed tank of water (increasing pressure above the water). Now the column can easily exceed 32 feet (the higher the pressure above the water in the tank, the higher the column). Assuming sea level and STP, the max is 32 feet (for water). Fluids with higher density will yield a lower column and vice versa.

        • Nate says:

          No Gordon, you are quite wrong again. The 32 feet comes from atm pressure 10^5 N/m2. Consider a pipe 1 m^2 cross sectional area will have a force of 10^5 N on water inside it, which is the weight of 10^4 kg, which is the weight of water in a 10 m length of the pipe.

          Thus water can be lifted by about 10 m by atm pressure

          • Lewis says:

            You guys are beyond me on the math and science.

            My experience was that I laid the pipe across the top of a hill, probably close to 35′ vertical from the intake. I shut off both ends and filled the pipe from the top. After filling it I opened the drain end and it flowed as if the top were still open. I found it full of air.

            Where did the air come from?

            I was of the belief the water boiled. What you various gentlemen have led me to believe is that happens at about 32′ feet of head.

            So I moved it back down the slope, the long way around, the head is not as high, but the length is 150′ longer (the entire thing is about 800′ long). Anyway, it works on the lower level.

            Thank you all.

          • Gordon Robertson says:

            Nate…”Thus water can be lifted by about 10 m by atm pressure”

            We’re both wrong. See the first link at my reply to Tim S. It states clearly that the only factors affecting a siphon are gravity and molecular cohesion. Atm pressure has nothing to do with the lifting.

            The atm pressure plays a part in causing the water to boil when the water vapour pressure at the top of the siphon falls below atm pressure. That produces gases (cavitation) in the water which breaks the molecular cohesion and causes the suction due to gravity to fail.

          • Tim S says:

            For the record, surface tension is responsible for osmotic pressure and capillary flow. It is only effect at short radius. It is very weak in a large pipe and will not cause flow.

          • Robert Stewart says:

            As a thought experiment, imagine you have a pipe that is under water in a pond and it is full of water. Close one end of the pipe and draw it out of the water and lay it on the side of hill next to the pond. If you compute the pressure in the water column inside the pipe, neglecting the Bernoulli effect since the water is still, you will find that the pressure decreases with height by the factor

            (density M/L^3)*(G L/T^2)* (height L)

            This is called the hydrostatic pressure.

            As you can see, the units are consistent with a Force (MG) divided by an area (L^2), which is a pressure.

            So if you have a pond with a free surface at the bottom of a hill, and the pipe runs up the hill from the pond, the pressure in the pipe at elevation Z above the surface of the pond will be:

            P(Z) = P(pond) – density*G*Z

            Now imagine that an empty pipe is immersed in the pond at one end, then it goes over the hill, down the other side, and opens at an elevation lower than the pond. If you apply a suction to the open end, you might expect the water to flow out of the pond and up the pipe. And it will, for a while. As the suction is applied, the water in the pipe will rise as the atmospheric pressure on the surface of the pond pushes water into the pipe. But if the pressure drops so low due to the hydrostatic effect that the water at the top of the water column vaporizes (boils or cavitates) then the water will rise no farther. And the portion of the pipe above the water will be filled with water vapor. So, even if the water is not moving, there is a maximum height it can rise under the effect of the suction applied to the open end of the pipe. Note that if the pond is at a high altitude, the pond’s surface pressure will be lower, and so the height the water can rise in the pipe before it boils will be lower. Also note that the density of the water is temperature (and salinity) dependent, as is the partial pressure of the water. So these factors will also determine the maximum height of the siphon. And once the water is drawn over the hill, and it begins to flow, then the pressure will be lower due to the Bernoulli effect, and this could also cause the siphon to break.

          • Eric says:

            Thanks Nate. I accidentally thanked “Tim” above. No face to name, so I mixed it up. You got it. See my reply to Tim above.

        • Tim S says:

          All flow is by force of positive pressure. Period. This is the very basics of Fluid Mechanics 101. With the exception of very high viscosity polymer melts, nothing, I say again, NOTHING in fluid mechanics is ever pulled by vacuum. Low pressure including vacuum is simply the area of low energy that the high pressure acts upon, ALWAYS!!!

  18. ren says:

    Residents in nearby Point Pleasant were allowed to return Tuesday, three days after they received an evacuation advisory.

    Robinson said he doesnt expect the upcoming rain to hit the area as hard as it did last week, but nothing is definite.

    These levees have been pounded and the ground is soaked, Robinson said. We need residents to stay on alert whether you live near a levee or an area thats been flooded before.

  19. ren says:

    The water level in Oroville significantly reduced.

  20. ren says:

    Meanwhile, at Shasta Dam… maximum water releases, storage at 95% and storms on the way
    Feb 15, 2017
    Shasta Dam on Tuesday, Jan. 14, 2017, was releasing its maximum amount of water, 79,000 cubic feet per second. Shasta is currently at 95 percent of capacity and more storms are on their way.

  21. Scott Gates says:


    In the 92 hours since last Sunday afternoon when they upped the outflow rate to 100,000 cfs, officials have dropped the level from 901.65 to 866.75 a drop of 35 feet. They have released 524,312 acre feet over 92 hours
    Total capacity 3,537,577 minus current level 3,039,414 equals 498,163 current available capacity. That number will increase as they continue outflows.

    The avg outflow last 24 hours is appx 6100 ac ft/hour at 100,000 cfs. Operators have enacted a planned reduction to 85,0000 cfs due to levels reaching the top of the main spillway intake channel cut so as not to cause erosion in the intake channel.

    Flood control elevation 850
    Capacity at 850′ 2,808,349
    Maximum capacity at 900′ 3,537,577
    Reserve at 850 729,228

    Current Elevation 866.75
    Current capacity 3,039,414
    Current reserve 498,163

    Estimate in/hr at 85,000 cfs 4.17 inch/hour
    Est time to 850′ at 85,000 cfs 48.16 hours

    (as of 1PM PST – 2/16/17)

    During the major rainfall event in early Jan 2017, I believe appx 15 inches fell in the area. During the appx 18 hour peak inflow period on 1/8 and 1/9 inflow rates averaged appx 135,000 cfs with a peak of appx 155,000 cfs.

    Significantly increased inflows (60,000 cfs and higher) ran from the morning of 1/8 thru midday 1/11 reservoir level was appx 793′ on 1/8 and appx 842 midday 1/11 an increase of appx 49′ or appx 676,740 acre feet.
    There was no appreciable outflow during this entire 3 day period.

    We currently have appx 500,000 acre feet of storage available and should have more than 700,000 by Saturday.

    There is currently enough storage to handle nearly 75% of the inflow from the current storm and even IF it is as STRONG as the January one in the next 48 hours there should be enough available storage capacity to handle 100% of the inflow from a 15″ January type super storm without running the spillway at all.


  22. ren says:

    The reduced temperature of the northern Pacific indicates the extent of the winter jet stream and demonstrates the weakness of the polar vortex.

  23. ren says:

    2.16 Snow Before You Go: 3 Storms, 3 Feet
    15th February 2017 | METEOROLOGIST CHRIS TOMER
    Copyright: Meteorologist Chris Tomer
    Three storms are lined up for the West Coast, guided by a strong jet stream. Smaller pieces of those storms will move across the Intermountain West along with abnormally warm air. In the Northeast, it turns cold and dry after a coastal storm departs on Thursday.

    California: Three different storm systems are lined up between Thursday and next Tuesday. Each delivers heavy rain and snow above 7,000 ft. plus high wind gusts. Tahoe ski areas south to Mammoth can expect 1-2 feet of snow accumulation from each storm. I expect this storm cycle to push Heavenly, Kirkwood and Mammoth over the 500-inch mark for the season so far.

  24. ren says:

    “I’m in 100% public safety mode, said Assemblyman James Gallagher (R-Yuba City), whose district line runs across the dam itself. “We’re just trying to make sure we get through this crisis, and people are kept safe through this whole thing.”

    But Gallagher has talked about the need to boost the states investment in reservoirs, and he expects to return to the topic in the future.

    “Once we get through this, I’m absolutely going to be talking about how this underscores how we need to invest in our infrastructure, and ensure that all of our infrastructure is being properly maintained, he said. That should be a top priority in California’s budget every year.

    The current situation puts an exclamation point on that, Gallagher added.

  25. ren says:

    In the area of Yuba City rain will gradually potentiate.

  26. ren says:

    Sacramento total inches of rainfall, October 1-February 10
    The federal government has tracked daily rainfall in downtown Sacramento for 100 years. This chart shows rainfall totals from October 1 through February 10 of each water year since 1915-16.

  27. ren says:

    Despite the heavy rain helicopters continue to strengthen the dam in Oroville.

  28. ren says:

    Another storm also will reach California.

  29. Darwin Wyatt says:

    I hope a flume for the emergency spillway is part of the fix. Sure beats a cliff face.

  30. ren says:

    Circulation in the lower stratosphere means continued rain in California.

  31. RAH says:

    It ain’t over till it’s over and it ain’t near over yet:
    70 deg temps in the mountains? Supporting reservoirs full? Nope, there is still the potential for disaster to come:

  32. ianl8888 says:

    > ” Now that the geology of that hillside has been revealed …”

    Revealed by predictable erosion ?

    As a (retired) geoscientist, why wasn’t the geology revealed by drilling at the design stage ?

    I do hope there is a good answer to that question.

  33. Ѽ says:

    Nice post. I was checking continuously this weblog and I am impressed!

    Extremely helpful information particularly the closing part 🙂 I care
    for such info much. I was looking for this particular information for a very
    lengthy time. Thank you and best of luck.

  34. ᥬ `ѩ`ԩ` says:

    ҪȡQƷ ֥ɥԩ`rӋ
    õһƷ|́ ˽_΄٤ФФǤ
    ˚ݥ֥ɥԩ`rӋ ߵȼrӋɣ
    NƷ|ꥢ븶Ф Ʒ䣡

    ᥬ `ѩ`ԩ` https://www.b2kopi.com/product/detail.aspx?id=7091

Leave a Reply