The Lake Pontchartrain Basin

 

• The Lake Pontchartrain Basin (inset) is a complex watershed comprised of many quite distinct ecosystems surrounding the actual Lakes Pontchartrain (large lake in the box) and Maurepas (smaller lake to the left of Lake Pontchartrain). Lake Pontchartrain is actually not a lake, but a large, shallow estuary in which saltier waters from the Gulf of Mexico mix with the fresh waters fed to Lake Maurepas from area rivers, bayous and streams.
  
  
• These two lakes are connected together by a narrow channel called Pass Manchac. Both lakes are fed by numerous streams and rivers from the hillier regions to the north.
  
  
• The exit flow to the east of the entire system is restricted by two narrow channels, the Rigolets and Chef Menteur Pass. This dramatically slows the volume of water that can flow from the Basin into nearby Breton and Chandeleur Sounds and ultimately the Gulf of Mexico.