geography from watershed divides

I like looking at topographical maps. I found it useful to study geography by looking at natural boundaries like watersheds and their divides. High ridges channel water in the valley between them, where civilization lies, and form boundaries between regions.

For example, continental US has a relatively simple topography characterized mainly by the Cascades-Sierras, the Rockies, and the Appalachian. Continental China, on the other hand, is a lot more complicated, unimaginably complicated, in fact, that it is almost incomprehensible when reading the profuse amount of written descriptions that exist. But I haven’t found a satisfactory visualization on a map, which is a shame, so it is time to make one.
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