All very good points. I remember only a little from jr high Earth Science, but I remember lots from college geography courses. The bottom line is that, as our illustrious post leader pointed out, water must flow downhill and/or gather in lowland areas. It is very good advice to figure your terrain features and mountains BEFORE placing rivers because I tend to think you only get a say in one or the other. Mountains tell you where rivers can be, and vice versa. As for the bit about water tables and springs, it makes sense, but it's also pretty deep (no pun intended). If most other mappers are like me they get a blank outline and then stare at it dumbfounded about what to do next. Great, I have a shape of the landmass......now what? Figuring out the surface terrain is enough of a task without trying to incorporate soil density.