I understand the calculation - I did it myself in the OP - but what I'm curious about is what you think is wrong with the source of the Mississippi being around 6000 metres further from the centre of the earth than its mouth?
See the answer for Trailblazer. As much time as r1-r2 is a positive number, the Mississippi is flowing uphill. I am not allowed to introduce an acceleration like that from the spinning of the Earth because that would result in water speeds which are not matched by reality. It is much easier to change the geodedic systems.