Ems (river, Germany) (ancient Amisia), river, northwestern Germany. Rising in North Rhine-Westphalia (Nordrhein-Westfalen), in the Teutoburger Wald near Bielefeld, it flows northwest and then north through Lower Saxony (Niedersachsen) east of the Netherlands border. Southeast of Emden it empties into Dollart, its estuary on the North Sea, after a course of 372 km (231 mi). Near the close of the 19th century the Ems was canalized for a distance of 69 km (43 mi); the Dortmund-Ems Canal (226 km/165 mi long) was built in 1892-1899 to connect the industrial Ruhr district with the Ems River and the North Sea. Extensive drainage was effected on the lower course of the Ems in the late 1920s; oil and natural-gas fields were developed after 1940.