The Emscher is a relatively small river and tributary of the Rhine, flowing through the Ruhr area in North Rhine-Westphalia in western Germany. Its total length is 84 km with an average discharge near the mouth into the lower Rhine of 16 m³/s (cubic metres per second).The Emscher has its source in Holzwickede, east of the city of Dortmund, and flows west through the Ruhr area.