17Watersheds and Divides all of the land area whose water drains into a stream systemstream systemlarge river and all its tributariesEach tributary in a stream system has its own watershed and divides, but they are all part of the larger stream system to which the tributary belongs.
18NC WatershedsNC has 12,200 km of rivers and streams
33Lakes and Freshwater Wetlands A lake is a depression that collects and holds water.Reservoirs are lakes made for storing water for a community’s use.
34Origins of Lakes Natural lakes form in different ways. Oxbow lakes: streams cut off meanders and leave isolated channels of water.Lakes can form when stream flow becomes blocked by sediment from landslides.
36Origins of Lakes Natural lakes form in different ways. Cirque lakes: depressions left by valley glaciers fill with water.Kettle lakes: blocks of ice left by melting glaciers melted.Some lakes are formed when the ceilings of limestone caverns collapse leaving depressions that fill with water.
37Lakes Undergo Change Lakes are temporary water-holding areas. Eventually lakes fill in with sediment and become part of a new landscape.
38Freshwater WetlandsA wetland is a land area that is covered with water for a large part of the year.Wetlands include environments commonly known as bogs, marshes, and swamps.
39Freshwater WetlandsBogs receive their water from precipitation and tend to be rich in peat moss.
40Freshwater WetlandsMarshes frequently form along the mouths of streams and in areas with extensive deltas.Marshes have tall grasses.
41Freshwater WetlandsSwamps are low-lying areas often located near streams.Swamps have shrubs and trees.
42Freshwater Wetlands A filtering system Habitats Pollutants Sediments Pathogenic bacteriaHabitatsMigratory birdsWater birdsEndangered species
43Freshwater WetlandsFrom the late 1700s to the mid 1980s, the continental United States lost 50 percent of its wetlands.