“...and it will take weeks or months dor these floodwaters to recede...”
Well...the new Addicks temporary level sensor lives on a seperate page, which includes another figure labelled “ reservoir storage acre feet.”
https://waterdata.usgs.gov/tx/nwis/uv/?site_no=08073000
Figure they give, from 0130 8/29/17, is 178,000 acrefeet. Seems maybe low, but let’s plug it in.
178,000 times 208 times 208 (1 acre) is 7,700,992,000 cubic feet.
At 8000 cubic feet per second controlled gate outflow, it’ll take...hmm carry the one...962,624 seconds to unload the reservoir. Divided by 3600 seconds per hour, divided by 24 hrs per day...
11 days, 3 hours, 23 minutes, 45.6 seconds. Set your watches.
(That’s to drain what’s in it now... or, more accurately, what was in it 2 days and 2.5 hours ago. It’s filled a bit since. And...there’s still a huge flow into it, ongoing, even though levels have “crested.”)