Weser River, major river of western Germany that serves as an important transport artery from Bremerhaven and Bremen. Formed near the city of Münden by the union of its two headstreams—the Fulda and the Werra—the Weser flows 273 miles (440 km) northward through northern Germany to the North Sea. The major tributaries of the Weser are the Aller, Lesum, Geeste, Diemel, Ochtum, and Hunte rivers.
Just below Minden, the Mittelland Canal crosses the Weser by aqueduct and connects the river within the Ruhr district and the Rhine River in the west and the waterways of Berlin in the east. For 84 miles (135 km) between Minden and Bremen, the river has been straightened and provided with eight hydroelectric dams. As a result, this part of the river is navigable for ships up to 1,200 tons deadweight and accounts for a large percentage of all the shipping traffic in the lower Weser harbours. Downriver further canalization permits North Sea tides with a range of 11.5 feet (3.5 m) to penetrate to the Bremen Dam. The Küsten Canal links the lower Weser to the Dortmund-Ems Canal, and another small canal leads from Bremerhaven to the lower Elbe River. The principal cities along the river are Bremerhaven, Bremen, Münden, and Kassel. Pollution has taken its toll since the 19th century, and the once-abundant salmon in the river have now completely vanished.