Amerindian origin, this naming has been deformed (often in the form of Maska or Masca, after which the inhabitants of Saint-Hyacinthe are named). It was officially named Rivière Yamaska 5 December 1968. Geography Hydrography The drainage basin of the Yamaska measures ; its average debit at the end is of , this is considered relatively slow compared to Richelieu at and Saint-François at rivers, the nearest streams; it is however subject to seasonal fluctuations (with a record flow of in the spring (linked to the snowmelt) and in the fall (caused by precipitation), and minimums of in winter and summer. There are few bodies of water in the Yamaska's basin, only six are larger than one square kilometer, of these only three are natural: Brome, Roxton, and Waterloo lakes. River's Course Starting at an elevation of north of lac Brome, it flows westward until it reaches Farnham; this section is at the feet of the Appalachian Mountains, it receives two tributaries: North Yamaska River (French: Rivière Yamaska Nord) passing through Granby, and Yamaska South East River draining Cowansville, after which it turns northward and enters the Great Lakes–St. Lawrence Lowlands (lowlands of the Saint-Lawrence) and meets its main tributary Rivière Noire (Black River) at Saint-Damase, passing through its biggest agglomeration, Saint-Hyacinthe; it continues towards its mouth at Lake Saint Pierre, West of Saint François Bay. Tributaries Among its main tributaries are Noire, South-East Yamaska, and North Yamaska rivers. Left tributaries (West Shore) Rivière Pot au Beurre (Yamaska River tributary) Le Petit Chenail (Yamaska River tributary) Saint-Louis River Salvail River South-West Yamaska River Yamaska South East River Right tributaries (East Shore) North Yamaska River Rivière à la-Barbe Noire River Rivière le Renne Jaune River Rouge River Chibouet River David River Regional County Municipalities and local municipalities crossed Brome-Missisquoi: Lac-Brome, Bromont, Brigham, Farnham La Haute-Yamaska: Saint-Alphonse-de-Granby, Granby Rouville: Ange-Gardien, Saint-Césaire Les Maskoutains: Saint-Damase, Saint-Hyacinthe, Saint-Barnabé-Sud, Saint-Simon, Saint-Hugues, Saint-Louis, Saint-Marcel-de-Richelieu Pierre-De Saurel: Saint-Aimé, Massueville, Saint-David, Yamaska Nicolet-Yamaska: Saint-François-du-Lac Biodiversity A varied fauna and flora exists along the Yamaska, reflecting the various regions it traverses; species of birds, fish, amphibians, reptiles, mammals, crustaceans, insect, fungi, lichen, algae and many more populate its waters, banks, and surrounding marshes. Pollution has greatly affected the nature that used to thrive in and around the river, reducing the number of species of fish from 70 to 33 between 1963 and 2003; to counter this the Quebec government proceeds