What do you call the body of water into which a river flows?

Solution 1:

This is a decent list of geological terms, and it doesn't have any word to specifically identify the relation of a river to its final outflow point (where it discharges). Which might not be into an ocean or sea - sometimes it's a desert basin.

I think mouth does well enough for the actual place where the river ends (assuming it doesn't just peter out in the desert), but that doesn't really embrace the whole body of water. I wouldn't object to outlet or outflow either, but I doubt they're commonly used in this exact context.

In short, I don't think there's a "real" technical term - but I'm not a geologist, so I don't know. The best I can come up with is terminus. For example, the Awash River drains into Lake Abbe, which is described as its terminus. Also the Black Sea is the terminus for a number of large rivers.

Solution 2:

Unless there is an arcane word for it, I would call it the river's destination.