The "Southwest Branch Saint John River" rises at the mouth of the "Little Saint John Lake" which straddles the border between the Canada and the United States. This lake which empties at the North is surrounded by mountains. The "Little Saint John Lake" is located on the East side of the watershed line corresponding to the crest of surrounding mountains. The Metgermette North River drains the Northwest side of this watershed slope. The West slope falls toward "Hurricane Pond" for which water empties on Southwest, through tributary "Hurricane Brook"; then the current runs down Southwest successively into Dole Brook and North Branch Penobscot River. The mouth of the "Little Saint John Lake" is located on the Canada-US border:
south of the top of a mountain Maine, whose altitude is ;
to the southeast from the village of Saint-Zacharie, Quebec;
From the mouth of the "Little Lake St John", the "Saint John River West" runs on of which delimiting the Canada-US border in its upper part and then flows on in the Maine. Its course describes the following segments: Higher Courses of the "Southwest Branch Saint John River"
Northward, up to a stream ;
Northward, up to a stream ;
Northward, meandering up to a stream ;
to the northwest, winding up to the discharge of Lake Joli ;
to the northeast, to the limit of the township of Langevin of Lake Veilleux and Lake Croche.
Intermediate Course of the "Southwest Saint John River"
At its confluence, the "Southwest Branch Saint John River" joins the "Northwest Branch Saint John River" whose source is at the mouth of Lake Frontier, in Quebec. This junction of the confluence of the two rivers is the head of the Saint John River. From the confluence of the "Southwest Branch Saint John River", the Saint John River flows to the East and Northeast through the Maine; then East and Southeast through the New Brunswick. The Saint John River flows on the North bank of the Bay of Fundy which opens to the Southwest to the Atlantic Ocean.
Toponymy
The name "Southwest Branch Saint John River" derives from the name of its parent river, the Saint John River. The cardinal points integrated in the place-name distinguish the two main tributaries of the upper part of the Saint John River. During his exploratory expedition of 1604 of the south coast of current New Brunswick, Samuel de Champlain named this river the Saint John River because it is consistent with the saint of the day in the calendar of Christendom. In history, the current Southwest Branch Saint John River was commonly referred to as "Saint John River", especially in an 1863 report of the surveyor Eugene Casgrain, describing the township of Daaquam. The editions of 1914 and 1925 of Dictionnaire des rivières et lacs de la province de Québec refer to the hydronym of "St. John River". The 1925 map of township Metgermette North indicates "St. John River West Branch" and that of Daaquam township of 1927. Subsequently, several maps and documents published refer to the cardinal point. The "Répertoire géographique du Québec" of 1969 indicates "Rivière Saint-Jean". In 1975 the "Commission de toponymie du Québec" officially changed this hydronym to Rivière Saint-Jean Sud-Ouest. The place name Rivière Saint-Jean Sud-Ouest was formalized on December 2, 1975, by the Commission de toponymie du Québec
