From PathfinderWiki

The Brookwall is the only major river that rises and flows fully within the county of Odranto in Ustalav. It has its source in the plains in the east of Odranto near the border with county Barstoi. The Brookwall flows for about forty miles in a west-north-westerly direction and is swelled by the waters from the lake called the Baileywell just past its half way point. It is a tributary of the important Vhatsuntide River, which it meets at the northern edges of the Foxfall woods and on the western border of Odranto with its neighbouring Lozeri county.1