The glaciers over North America and Asia only 20,000 years ago would dwarf that reservoir. They put 400 feet of water that is now in the oceans on top of the continents.
In the Seattle/Tacoma area where I am, down to a bit south of Portland, Or., the estimates are that the glaciers were about a mile thick.
That’s part of the reason I don’t get all bent about salmon being “exterminated” from the local rivers. 13K years ago, there weren’t even any rivers!!
This is why global warming is essential! When the Greenland icecap melts it will move a mass of water to a lower elevation, thereby speeding up the earth’s rotation to counteract the 3 Gorges dam!
Voila! Problem fixed! /sarc
;-)