Svartån in Västmanland County, Sweden is 91 kilometers long. It passes through the towns of Skultuna and Västerås and has its outlet in Mälaren. The name Västerås derives from the Sueco-Latin term Västra Aros meaning "western outlet." The river played an important role in the industrial development in this region from the 17th century until the early 20th century as a source for hydropower. Small-scale hydroelectric dams are located in Västerås (the Turbine House and at Falkenberg's Mill), Skerike, and Skultuna, among others.
https://en.wikipedia.org/wiki/Svart%C3%A5n