Yamaska River

The Yamaska River is a river in southern Quebec, Canada.

Its source is the Sutton Mountains region of the Eastern Townships of Quebec. It flows north-west to Farnham and from there north to the Saint Lawrence River near Sorel-Tracy. Altogether it is 177 km (110 mi) long with a drainage basin of 4784 square kilometres.

Its basin is characterized by urban, industrial, and intensive agricultural use. Consequently the river is seriously polluted, especially from agricultural waste and pesticides. Nevertheless, many municipalities use the river as their source for drinking water.

Its name comes from an Amerindian name meaning "where rushes grow", referring to the abundant rushes in the marsh at river's mouth (Lavallière Bay). The name underwent many mutations: Maska, Ouamaska, Hiamaska, and Hyamaska. In the Abenaki language, the site was designated Mamaska, meaning "toad".