What is a suitable word to describe a place where two rivers meet?

In geography, a confluence is the meeting of two or more bodies of water. It usually refers to the point where two streams flow together, merging into a single stream.

You can also use the word junction, as in the

junction of the Grand and the Green

near Moab, Utah.

It can either be a tributary or a distributary, where a river joins another or separate from one respectively.

It is called a confluence. A tributary is a smaller river joining a larger one. A distributary is a river flowing into the sea.

You could also use the word "fork" which is less formal. A watershed is all of the land area that a given body of water drains.