Charting a 3D graph?

Hi there
I am currently working on a University project and have to chart flow rate in a river system with regard to river depth.
Ideally I would like a chart that is the river depth as a line graph across horizontally, with the area filled in with a colour coded flow rate chart. So the points in the depth area may be red for faster, blue for slower etc.

Does anyone know if this is at all possible or if i'll have to get some paper and pens!!!!

Thnks

Murray Gallacher
Scotland