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University of Toronto Scarborough
Environmental Science
Carl Mitchell

Freshwater Systems Roughly 97.5% of earths water resides on the oceans and Is too salty to drink or to use to water crops. o 2.5% is considered freshwater , water that is relatively pure, with few dissolved salts. Some of which is tied up in glaciers, icecaps and underground aquifers, just over 1 part in 10000 of earths water is easily accessible for human use. Water is moving among reservoirs via the hydrological cycle o As it moves it redistributes heat, erodes mountain ranges, builds river deltas, maintains organisms and ecosystems, shapes civilizations, and gives rise to political conflict Rivers and streams wind through landscapes Water from rain, snowmelt, or springs runs downhill and converges where the land dips lowest, forming streams, creeks or brooks. o These watercourses merge into rivers, which eventually lead to ocean. A small river flowing into a larger one is a tributary The area of land drained by a river and all its tributaries is that rivers drainage basin or watershed Rivers shape the landscape through which they run. o The force of water gradually eats at the outer shore, eroding soil from the bank Meanwhile, sediment is deposited along the inside of the bend, where water currents are weaker. Because of this, river bends become exaggerated in shape Eventually a bend may become such an extreme loop (oxbow) that water erodes a short cut from one end of the loop to the other creating a direct course. (oxbox lake) Areas nearest a rivers course that are flooded periodically are said to be within a rivers floodplain Agriculture thrives in foodplains and riparian (river side) forests are productive and species rich. Wetlands include marshes, swamps and bogs Wetlands are systems that combine elements of freshwater and dry land. in freshwater marshes shallow water allows plants to grow above the waters surface. Swamps also consist of shallow water rich in vegetation, but they occur in forested areas. o Also created when beavers build dams across streams with limbs from trees they have cut, flooding wooden areas upstream. Bogs are ponds thoroughly covered with thick floating mats of vegetation and can represent a stage in aquatic succession. Wetland are extremely valuable as habitat for wildlife & also provide important ecosystem services by slowing runoff, reducing flooding, recharging aquifers, and filtering pollutants. Lakes and ponds are ecologically diverse systems The region ringing the edge of a water body is named the littoral zone. o Water is shallow enough here that aquatic plants grow from the mud and reach above waters surface o Has a lot of crayfish, snails, insect larvae for fish, birds, turtles and amphibians to feed off of. The benthic zone extends along the bottom of the entire water body o Many invertebrates live here feeding on detritus or preying on one another Sunlight penetrates shallow waters of the limnetic zone o Limnetic zone supports phytoplankton
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