Another River Runoff app: up and downstream for anywhere in the world

I made this a couple of months ago and shared on HN. After seeing a similar app on the front page yesterday [0] I thought I'd share it again!

This one is less "high-res" since the NLDI API doesn't exist for the whole world so I had to cook up my own method based on HydroSHEDS data.

[0] https://news.ycombinator.com/item?id=27297689