 Map: As Rivers Run To It – The Lake Champlain Watershed
Lake Champlain is affected both by activities along its shore and in distant parts of the Lake Champlain Basin - that area which drains into the lake. Streams and rivers carry water, sediments, nutrients, toxic substances, fallen trees, seeds, and a wide variety of living and dead organisms to the lake from areas tens and even hundreds of miles distant. The effect of this input and of human activity along the shore depends on the lake’s circulation, geology, plant and animal life, and other factors-which can vary widely in different parts of the lake.
In general, pollution problems tend to be most prominent in shallow regions where flushing and dilution are reduced and pollutants can collect. These same shallow areas are where tributaries enter the lake, bearing pollutants and sediments, and where human settlement is concentrated.
Variations in water temperature and depth also make for different plant and animal habitats: 30-pound carp and longnosed gar up to four feet long like the warm water and high turbidity of the South Lake, while lake trout and Atlantic salmon prefer the cold deep water of the Broad Lake.
Lake Champlain has five distinct regions that act like five different lakes:
Missisquoi Bay:
Extends from the delta of the Missisquoi River into Quebec. Water flows south into the inland Sea. Like the South Lake, Missisquoi Bay is warm, shallow and heavily overgrown with aquatic plants.
Inland Sea:
Runs along the east side of the Champlain Islands and includes the narrow passage between North Hero and Alburg peninsula. Also called the Northeast Arm.
Malletts Bay:
Lies to the southeast of Grand Isle, set off from the Broad Lake by an abandoned railroad causeway. Because of this causeway and an auto causeway on the north side of the bay, it has the most restricted circulation of any lake region.
Broad Lake:
Extends from the narrows at Crown Point north to the outlet at Ash Island. Characterized by deep water (up to 400 feet) that stays cool throughout the year.
South Lake:
Runs from the mouth of the Poultney River to Crown Point and includes South Bay and East bay. The narrow South Lake is choked in many areas with aquatic plants -- including non-native water chestnut and Eurasian watermilfoil -- that thrive in its warm, shallow water.
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