I think these numbers are correct. I was given some free smoke so my brain is in a bit of a fog.
Keystone pipeline is 36". Maximum of 700,000 barrels a day or about 30,000,000 gallons a day.
https://en.wikipedia.org/wiki/Keystone_Pipeline
Hoover dam releases 12,700 cubic feet per second. 762,000 c/f per minute or 5,700,000 gallons per minute.
https://www.usbr.gov/lc/region/g4000/hourly/rivops.html
The Colorado takes less than 6 minutes to exceed Keystone daily output.
And then there is the altitude change.