Here’s a documentary about the 1983 near-catastrophe at the spectacular Glen Canyon dam on the Colorado River near the Arizona-Utah border in the upper reaches of Grand Canyon. Lake Powell is about 8 times the volume of Lake Oroville, so a dam collapse would have been apocalyptic:
Strikingly, as Part 2 below recounts, one way they kept the dam from overflowing was by temporarily raising the height of the dam by installing vertical flashboards in a two day long effort. Could something similar be done along Oroville’s 1730 foot emergency spillway? How long would it take to add, say, 8 feet to the height of the emergency spillway?
One thing to keep in mind is that the immediate fight to save Glen Canyon dam went on for several months in the summer of 1983. And this was followed by a sprint in 1984, which turned out to be even wetter than 1983, to make substantial repairs and improvements to the spillways. All told the effort took about 14 months.
Thanks to Lake Powell Realty for finding these videos.
At the Oroville Dam today, a half-inch of rain fell in the early morning hours. Because the watershed is roughly 144 times as large as the lake, that would, theoretically eventually convert to a 6 foot rise in the lake (or perhaps more if more precipitation fell at higher altitude, as usually happens). So far, the inflow into the lake hasn’t gone up much and they’re continue to drain the lake down the main spillway. It’s now down 37 feet from the emergency spillway’s brim.
Outflow down the main spillway has been cut from 100,000 cubic feet per second to 80,000 cubic feet per second. The goal is to lower the water level backing up the river to the dam so that the power station can be restarted, which would allow an additional 13,000 cfs of outflow. They are dredging the river to remove the partial dam caused by debris from the hole in the spillway landing in the river. (There is also some concern about heavy intake of water damaging the bottom of the lake, although I’m not sure if that is relevant at present or only at lower levels of the lake.)
Weather Underground is forecasting 7.85″ of precipitation over the next seven days, followed by 3 days of sun, at the small town of Feather Falls at 2900 feet elevation inside the reservoir’s watershed. At a rule of thumb of one inch of precipitation eventually equals a 12 foot rise in the reservoir, that would add about 100 feet to the lake’s level. On the other hand, if they can pump out, say, 8 feet per day over the next ten days, that would lower the lake 80 feet, which, with the current 36 foot buffer, would keep the lake 17 feet below the emergency spillway.