The Concord River begins at the confluence of the Assabet and Sudbury rivers in Concord and flows northward to join the Merrimack River in Lowell. The Lower Concord segment runs from North Billerica, upstream of the Talbot Mills dam, to where the Concord River joins the Merrimack River. This segment flows through the highly urbanized and industrialized Lowell region. It includes two dams, one of which completely blocks anadromous fish migration and recreational passage. It also includes world-class white water for rafting and new riverfront trails that are being added to annually.
