Ah ha, yes. That's not a canyon, but rather an escarpment. So the water flows over a waterfall and the runs to the sea. If it were a canyon you'd be dead right.

As for the uphill bit, there are a couple of places where it's questionable (for those that are very keen - there's a section where a river flows over the shoulder of a mountain) but I'l go in and fix those. That's the inevitable danger of drawing the rivers in first.

The snow is probably just a matter of me making my highlights too bright. There should only really be a suggestion of snow along the northern mountain range. I'll tone down the sharp bright highlights elsewhere. The mountains are supposed to be jagged and sharp as they were created recently. So I wanted them to have clean sharp highlights on the crests and edges.