From publisher blurb:
The Thard, Hârn's second-longest river, has dominated the economic and cultural history of the island's western region for centuries. Its gentle and meandering course has created a fertile alluvial valley that has been the cradle of several Hârnic civilizations. Coranan, Shiran, and Golotha were all founded on its banks. Today, the river is a major avenue of trade between the Thardic Republic and the kingdoms of Kanday and Rethem.
The Thard River article covers the history and economic importance of the route, tells what travelers can expect on each segment of the trip, and describes the basics of river trade. It also provides descriptions of some interesting people your PCs may encounter, including the crew of a typical river freighter.