A river's depth is basically defined by the water table. That's how it stays full of water instead of simply draining into the ground. The first diagram on the

A river's depth is basically defined by the water table. That's how it stays full of water instead of simply draining into the ground. The first diagram on the Wiki article for water tables shows this: https://en.wikipedia.org/wiki/Water_table https://en.wikipedia.org/wiki/Water_table (The first time I heard this was a big "aha" / "of course it works that way, how else would it work" moment for me. Ala XKCD 10000 [0]. Hopefully you're one of today's lucky winners!) [0] https://www.xkcd.com/1053/ https://www.xkcd.com/1053/