Not sure this is accurate as we've discovered that water can reside deeper in the Earth than previously imagined and in addition to that the density of water at the surface is different than at the bottom of the ocean. I suppose they are also accounting for the salt being removed too. But my argument is probably in the margin of error so what do I know?

https://www.technology.org/how-and-why/what-would-happen-if-....

So I feel like the USGS is exagerated.