Pretty cool site that lets you drop a raindrop and follow it to the ocean: https://river-runner.samlearner.com/
Strangely, I always dreamed of doing a documentary that would do exactly this. Thanks for posting.
I dropped a raindrop at my house and it correctly found the tiny local creek and traced it to a reservoir - I've heard that not a drop of water from the Sierra Nevada makes it to the ocean without passing through a human usage first (not counting evaporation)