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I still don't understand how water can raise an extra 10 feet over the spillway. Isn't a bathtub only as high as its lowest side?
by liberte82 9y ago
I still don't understand how water can raise an extra 10 feet over the spillway. Isn't a bathtub only as high as its lowest side?
- snowwrestler 9y agoInflow minus outflow rates determine the height of a reservoir. On the upstream side you have a big river basin. On the downstream side, pipes and a spillway. If the basin is catching a lot of rain, you'll need all the pipes and spillway to keep up with the inflow. That's part of the dam's design.
- hexane360 9y agoThe spillways can only transport so much water. If inflow is greater than that, you can build up above that point. Even a fast moving channel 10 feet deep is dwarfed by the flux of water that can be deposited by a heavy storm over a large area. Edit: for some concrete numbers, the reservoir was rising 0.5 ft/hr!! For reference, it appears the Addicks Reservoir has an area of 26,000 acres around this depth. That's 157,300 ft^3/s of inflow. Outflow was only 4,000 ft^3/s! Edit 2: Here's a visualization: http://i.imgur.com/usZAici.jpg http://i.imgur.com/usZAici.jpg
- ars 9y agoIt can happen if water is entering the lake faster than it can exit. That's why a river can crest much higher than the water lower than it - it's a dynamic level, not a static one.
- tajen 9y agoIt also just takes a wave (due, for example, to terrain movement) to go overboard and it drastically erodes the crest of the dam, starting a chain reaction between erosion of the crest and more water going through.