Brandywine
From Tolkien Gateway
The name given by Hobbits to the river the Elves called Baranduin; its source was at Lake Nenuial in the north, and it flowed southwestwards to reach the Great Sea near Eryn Vorn. For part of its length it formed the eastern border of the Shire.
Primula and Drogo Baggins, parents of Frodo, were lost along the river in a boating accident.