Oroville Dam: Water and Weather, Engineering and Erosion at the Nation's Tallest Dam

California is having a very wet winter, with multiple atmospheric rivers dumping feet of precipitation in the mountains. Oroville Dam on the Feather River, is the nation's tallest dam, is facing serious engineering challenges. This Storify has some of the best links to a rapidly evolving situation.

  1. Note: This storify is in reverse chronological order and will be updated as the situation changes. If you don't know anything about what's happening at Oroville, scroll down to the bottom and read upward.

    I expect that we will be hearing more about the problems at Oroville Dam for the rest of the winter and spring, because any further big rain and snow melt events will be challenges for the reservoir operation. Beyond that, the repairs, finger pointing, etc. will likely take the rest of year (and beyond). I will plan on updating this Storify "as events warrant."
  2. I compiled a picture-rich powerpoint show explaining the Oroville Dam crisis and context (up through 9:00 am 2/14/17) and made it available, below. There aren't a lot of words, but if you generally know the story and want something to share with others, hopefully this helps.
  3. If you want access to slides I compiled on hydrology, erosion, and timeline of #OrovilleDam events, they are here:  https://www.dropbox.com/s/ccex3qtlj14h2hc/Oroville.pdf?dl=0 
  4. Wednesday, February 15, 6:36 pm PST

  5. On Tuesday afternoon, the evacuation order downstream of Oroville Dam was finally lifted.
  6. Evacuation downstream of #OrovilleDam lifted. Here's hoping lake levels can be kept low enough that such an evacuation is never needed again  https://twitter.com/ER_DavidLittle/status/831621483218677762 
  7. By Wednesday afternoon, the lake was dropping dramatically.
  8. Lake Oroville down nearly 27ft. More than halfway to 50ft target drop. 100k outflow continues
  9. Oroville Dam: Crews work into the night to bolster eroded spillway as next storm approaches  http://sacb.ee/8TLp 
  10. But the weather forecast is ominous.
  11. Correx: Up to 12 inches of rainfall over the next *10* days in the #LakeOroville catchment basin. Already 221% of normal.

Not good. https://t.co/yJKmX7goXo
    Correx: Up to 12 inches of rainfall over the next *10* days in the #LakeOroville catchment basin. Already 221% of normal. Not good. pic.twitter.com/yJKmX7goXo
  12. @highlyanne 3 day running avg jet stream since early Dec shows west coast getting slammed pic.twitter.com/Y3P0mGIPc7
  13. Check out the sediment plume coming out of SF Bay and into the Pacific yesterday. https://t.co/kiAR6UfwWz
    Check out the sediment plume coming out of SF Bay and into the Pacific yesterday. pic.twitter.com/kiAR6UfwWz
  14. While we wait to see what happens next, the broader discussions of dam safety and levees, an even more endangered and undervalued piece of infrastructure than dams.
  15. "“That groaning sound you’re hearing throughout the Central Valley isn’t the dams – it’s the levees,” says Jeff Mount  https://twitter.com/RyanSabalow/status/831931473431138304 
  16. Oroville Dam isn’t the only piece of California flood infrastructure under strain  http://sacb.ee/8Td1 
  17. On a related note, once again, @ConnectedWaters #DamOrNot Twitter engagement did an awesome job at talking about the myriad ways that dams impact natural and human systems. This week was a double feature on Oroville Dam and Mosul Dam.
  18. Here's a small graphic I put together to compare the two, #OrovilleDam & #MosulDam! They are both kinda having a hard time #DamOrNot https://t.co/teipltXwAm
    Here's a small graphic I put together to compare the two, #OrovilleDam & #MosulDam! They are both kinda having a hard time #DamOrNot pic.twitter.com/teipltXwAm
  19. The more you read about both the #OrovilleDam & #MosulDams the more your stomach turns. Here's another graphic on their stories #DamOrNot https://t.co/ap1H9MsR7N
    The more you read about both the #OrovilleDam & #MosulDams the more your stomach turns. Here's another graphic on their stories #DamOrNot pic.twitter.com/ap1H9MsR7N
  20. The scenario is both are basically threatening imminent environmental, social and economic damage despite efforts to reduce those #DamOrNot
  21. Something that absolutely blows my mind is the lack of proactive response or thinking on both #OrovilleDam & #MosulDam. #DamOrNot
  22. Tuesday, February 14th, 9:30 am PST

  23. Someone tweeted and others retweeted the following factoid, and I felt the need to have a little lesson in water balances.
  24. If 100% of the runoff from one inch of rain in Lake Oroville's 3607 mi² catchment basin reaches the lake, it rises about 12 feet.
  25. That doesn't happen though unless the ground is completely saturated, the trees don't intercept any rain, and upstream reservoirs are full  https://twitter.com/DataPointed/status/831391364927545344 
  26. @drdrewsteen For a big event in already wet conditions, could get very high runoff ratio (spitballing ~70%), but most of the time much lower
  27. @drdrewsteen Average is only 2.3% of flow is surface runoff, rest moves in subsurface at least part of time (slower)  https://pubs.usgs.gov/sir/2004/5202/sir2004-5202.pdf 
  28. OTOH, I forgot to think about the change in storage of snow on the landscape, so we all fail in our own ways.
  29. Curious about the hydrology of Feather River basin? The @USGS did a great study, available free online  https://pubs.usgs.gov/sir/2004/5202/sir2004-5202.pdf  #OrovilleDam
  30. This exchange led to a question about how much water has really fallen on the Feather River watershed in the past few weeks.
  31. @highlyanne weren't there reports of big, 50 foot rise in lake over weekend? Did I read those wrong or did catchment get like 5 in of rain?
  32. .@TheEarthStory We're talking about the mountains here, so it's not impossible to get a big rain depth thanks to orographic effects.
  33. .@TheEarthStory Plus, you can melt stored water (i.e., snow) to deliver large volumes even if the total rainfall is lower.
  34. While I flailed a little trying to put my fingers on exact or basin-averaged numbers, Twitter came through. with the following beautiful images. The Feather River is southeast of Chico and northeast of Sacramento - so the white area on the maps below.
  35. With all that precipitation, of course the Feather River isn't the only watershed feeling the effects. While our attention has been focused there, rivers have gotten big up and down california.
  36. Don't look now, but for the first time since all this started in January, SJR expected to reach flood stage at Vernalis #caflood #cawater https://t.co/mDYsKTL3Dr
    Don't look now, but for the first time since all this started in January, SJR expected to reach flood stage at Vernalis #caflood #cawater pic.twitter.com/mDYsKTL3Dr
  37. The SJR is the San Juan River, flowing through the southern half of the Central Valley. Both the Sacramento River (in the north) and the San Juan River (in the south) are heavily leveed, and the risks of substantial levee failures are rising the longer we have very high flows.
  38. "It's falling apart out here," levee engineer on Tyler Island tells me. If fails, would be biggest Delta flood since Jones Tract in 2004
  39. Monday, February 13, 5:45 pm PST

  40. Picture of severe erosion heading upslope to base of emergency spillway. This triggered the evacuation order. #OrovilleDam (people circled) https://t.co/eAwkZ0hfMt
    Picture of severe erosion heading upslope to base of emergency spillway. This triggered the evacuation order. #OrovilleDam (people circled) pic.twitter.com/eAwkZ0hfMt
  41. The finger pointing has begun, particularly as we learn more about concerns raised in 2002 and again in 2005 that the emergency spillway could substantially erode if water were ever let down it.
  42. Engineers have known for decades that #OrovilleDam’s backup spillway was unreliable  http://sacb.ee/8She  by @RyanSabalow
  43. Meanwhile, by continuing to pass lots of water through the dam penstocks and the (damaged) regular spillway, the lake level is lowering by about 4" per hour. The goal is to bring it down by 50 feet, but that's going to take quite a while.
  44. 3:00 PM update at #LakeOroville for the emergency spillway at #OrovilleDam.  Lake is dropping ~4 inches an hour. https://t.co/sX2YEBoyKa
    3:00 PM update at #LakeOroville for the emergency spillway at #OrovilleDam. Lake is dropping ~4 inches an hour. pic.twitter.com/sX2YEBoyKa
  45. The California Department of Water Resources had a briefing at noon, and KQED has been reporting on it.
  46. .CA_DWR: Erosion in wrecked main spillway channel seems to have ended - water running clean.' #cawater #OrovilleDam #OrovilleSpillway
  47. VERY abrupt end to the @CA_DWR briefing. My take: Agency not ready yet to answer the 'who knew what when' questions. #cawater #OrovilleDam
  48. One thing Twitter is starting to speculate about is how much repairs are going to cost and how long they are going to take. I saw $100 million floated to repair the main spillway and that was before the problems emerged with the emergency spillway + the damage is likely continuing to get worse at the main spillway. There's probably more too that we aren't aware of yet.
  49. @highlyanne @TDSIanJames We also now probably have damage to the powerhouse, which they first tried to avoid by limiting main spillway flow.
  50. Now that the immediate crisis seems to have passed, let's take a few minutes to put this event in hydrologic context. It was the result of a series of big rainstorms called "atmospheric rivers." Atmospheric rivers that rain at high elevations (where there would normally be snow) are sometimes nicknamed the "pineapple express."
  51. Over 50” above normal precipitation during the last 90 days in the Feather River Basin upstream of Lake #Oroville https://t.co/3Zw43WjyI3
    Over 50” above normal precipitation during the last 90 days in the Feather River Basin upstream of Lake #Oroville pic.twitter.com/3Zw43WjyI3
  52. Flooding as a result of atmospheric rivers is nothing new to California:
  53. Situation as of Monday morning, ~2:30 am PST

  54. After I hopped off Twitter on Sunday evening, the situation at Oroville Dam got scarier as concerns emerged that the emergency spillway was at risk of failing. 180,000 people were evacuated from lowlying areas along the river overnight.
  55. Oroville is the primary reservoir for the State Water Project. 1/3 of Southern California's water is SWP water #OrovilleDam
  56. A dozen years ago, there were serious concerns that the lip of the emergency spillway would be undercut and fail if the spillway was ever used. That's exactly the situation we're in now, where there are initial signs of undercutting forcing emergency repairs.
  57. Evacuation order downstream of Oroville Dam is still in place, though hopefully immediate risk is fading since water levels are now below the lip of the emergency spillway and no more erosion should occur unless water starts spilling again. But here's a perspective on the scale of flood risk that we are talking about.
  58. The Earth Story (@theearthstory) has done a nice job of detailing exactly why the erosion at the emergency spillway is such a concern.
  59. Sheetflow finds a place where sediment is unstable, moves that sediment, and creates low ground that focuses water flow. #OrovilleDam
  60. Once low ground is created, water focuses into that spot, creating a deeper flow. General rule: deeper flow = more ability to move sediment.
  61. When water started moving over the #orovillespillway it started off moving as sheet flow, but rapidly plucked away sediment on the slope
  62. This created a channel in which erosion happened more rapidly than expected. Basically, it created a nickpoint.
  63. When they were forced to open the emergency spillway, sedimentary processes took over and started developing a channel
  64. Based on image from @GoldsteinStreet, headward erosion on  left side of the emergency spillway created a nick point moving towards the lake https://t.co/uy7Ow8q8hA
    Based on image from @GoldsteinStreet, headward erosion on left side of the emergency spillway created a nick point moving towards the lake pic.twitter.com/uy7Ow8q8hA
  65. The nick point in this channel reaching the lake is the uncontrolled failure referred to in press warnings for flooding. #OrovilleDam
  66. What don’t I know right now? The geology of this spillway will determine how this failure goes. Failure does not mean whole lake must empty.
  67. Per tweets by @CA_DWR they are hoping to airdrop rocks into the emergency spillway to slow the rate of erosion at the nick point.
  68. The goal now is to have the spillway wall hold up while the lake volume drops. If lake drops low enough to stop waterfall, situation stable.
  69. The next few links are some perspective pieces that I thought were good:
  70. As the editorial says, we cannot easily attribute a single weather event to climate change, but going from extreme drought to extreme wet fits the pattern of more extreme weather that we expect in a climate changed world. On the other hand, the editorial did not emphasize the need to make sure our nation's infrastructure is well maintained and engineered to cope with more extremes. I was surprised by that omission.
  71. My take on the longer-term outlook:
  72. If I were at #OrovilleDam, after current crisis has passed, I'd lower reservoir & try to keep it low for rest of winter to avoid spillways.
  73. But this response ignores fact that huge amount of water & power for California State Water Project comes from #OrovilleDam
  74. Regardless of how rest of winter plays out, the cost of repairs will be huge & take a long time & #OrovilleDam will be news for years.
  75. Sunday afternoon, February 12th,

  76. For historical perspective, a look at inflow to Oroville Dam. Past week surpasses anything seen since 2000 but dwarfed by 1997 #castorm https://t.co/Z201kxQXTk
    For historical perspective, a look at inflow to Oroville Dam. Past week surpasses anything seen since 2000 but dwarfed by 1997 #castorm pic.twitter.com/Z201kxQXTk
  77. 02/12/2017 12:00 - #OrovilleDam hourly numbers: 902.28 feet:  https://cdec.water.ca.gov/cgi-progs/queryF?ORO  Water overtopping aux spillway, but lake elev receding.
  78. #OrovilleDam Water will continue down emergency spillway today. Dam is at 101% of capacity (graphic) Photos: @CA_DWR #OrovilleSpillway pic.twitter.com/49Gh4qaWJJ
  79. Saturday February 11th

  80. Potentially we could get more big storms in California this winter + spring snowmelt, all flowing into a pretty full reservoir #OrovilleDam
  81. One thing to keep in mind re: #OrovilleDam is that it's likely to be an ugly & dynamic situation until repairs can be done...in summer
  82. #OrovilleDam is demo of need to adapt for #climatechange swap from snow to rain in the Sierra.
  83. Lake Oroville in #California nearing 100% capacity. Unprecedented water level for early February based on data back to the 1970s. https://t.co/SDHqpFOrr6
    Lake Oroville in #California nearing 100% capacity. Unprecedented water level for early February based on data back to the 1970s. pic.twitter.com/SDHqpFOrr6
  84. Drone view above the bottom of the Oroville Dam "Controlled" Spillway  https://youtu.be/n1eLcSQPS8Q  via @YouTube Excellent perspective of erosion.
  85. Zoom in and take a look! Our swollen waterways are visible from space today. Pretty incredible! #cawx #castorm #caflood https://t.co/zU9eVWrpgl
    Zoom in and take a look! Our swollen waterways are visible from space today. Pretty incredible! #cawx #castorm #caflood pic.twitter.com/zU9eVWrpgl
  86. Flow over auxiliary spillway between 6,000 and 12,000 cfs. No danger to dam or people. #OrovilleSpillway pic.twitter.com/DEetbZP9LV
  87. #OrovilleDam reservoir reaches 901 ft. Emergency spillway in use for first time. Inflows still exceed controlled outflows by 35,000 cfs . https://t.co/0ifoPivCNE
    #OrovilleDam reservoir reaches 901 ft. Emergency spillway in use for first time. Inflows still exceed controlled outflows by 35,000 cfs . pic.twitter.com/0ifoPivCNE
  88. #OrovilleDam inflow continues to exceed controlled outflow. Reservoir will rise until flow over emergency spillway equals inflow. https://t.co/WwUwe5CNe7
    #OrovilleDam inflow continues to exceed controlled outflow. Reservoir will rise until flow over emergency spillway equals inflow. pic.twitter.com/WwUwe5CNe7
  89. Friday February 10th

  90. So much water coming into the reservoir that flows down the damaged concrete spillway were ramped up to 100,000 cubic feet per second (cfs) and the possibility of having to use the emergency spillway was first publicly aired.
  91. It's unclear whether the emergency spillway at Oroville Dam will get used this weekend  http://sacramento.cbslocal.com/2017/02/10/dwr-may-avoid-emergency-release-from-oroville-dam/  but it's going to be intense
  92. Thursday, February 9th

  93. Thursday was the first day that the situation at Oroville came to my attention, though the problem with the main spillway was discovered on Tuesday. Basically, a huge hole had appeared part way down the concrete spillway, causing erosion of the underlying soil and rocks. Even though lots of water was coming into the reservoir, engineers reduced flow down the spillway in order to take a look and hopefully to decrease damage to the reservoir. Meanwhile, the maximum possible water was going through the penstock of the dam itself.
  94. DWR removing trees, debris in case emergency Oroville spillway is needed. Could run out of room Fri h/t @PeterGleick https://t.co/JmRt7nlUNR https://t.co/JMA8alIX8O
    DWR removing trees, debris in case emergency Oroville spillway is needed. Could run out of room Fri h/t @PeterGleick  http://bit.ly/2k5a2Oh  pic.twitter.com/JMA8alIX8O
  95. Video of the Oroville Spillway today at 11am. 35,000 cfs of water is currently being released over the #spillway....  http://fb.me/EjF7bncc 
  96. There is an emergency spillway that would be used before overtopping becomes imminent. But using regular spillway = best option.  https://twitter.com/PeterGleick/status/829428670578118656 
  97. The tweet above from me was correcting an erroneous tweet from Peter Gleick (below) (who otherwise has been pretty good on this event). It is important to understand that dams are built with multiple safety valves for progressively worse situations. Going over the top of the main face of the dam would be beyond the worst possible scenario that engineers imagined.
  98. The damage to Oroville Dam spillway is serious. If you cannot spill via #1 (see  marks on pic), you risk overtopping/eroding the dam (#2). https://t.co/r0lIUdnpbQ
    The damage to Oroville Dam spillway is serious. If you cannot spill via #1 (see marks on pic), you risk overtopping/eroding the dam (#2). pic.twitter.com/r0lIUdnpbQ
  99. Wow. A look at the growing crater in the Lake Oroville spillway after DWR crews finished testing it tonight:  https://goo.gl/ec168H  pic.twitter.com/QFCyVnhjmr