Confluence with

Hello. I am writing about the city of Granada, in Spain, and in the following sentence, I am not sure I am using correctly the preposition "with", after the noun "confluence". Here is the sentence: "This is the itinerary the river Darro follows before reaching the confluence with the water descending from the peaks of Sierra Nevada." Thanks in advance for your kind cooperation.

Can a river follow an itinerary? I thought they always followed courses. And usually rivers are described as reaching the confluence of another named river. I've never heard of a river "reaching the confluence with the water descending from ..."

Thanks, Linguisticks.