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Thermal Pollution : Dams

Water is also warmed when a river is dammed.  Dams slow the current of rivers and allow the water to be exposed to the sun more than if it were free flowing.  This ultimately results in an increased temperature of the entire river.

More dams = more thermal pollution

When rain falls, it soaks into the ground and is absorbed by soil and plants.  A lot of it even reaches the underground water table (where a lot of our drinking water comes from).  When parking lots and buildings prevent the water from soaking into the soil, the water has no choice but to run off (this is where we get the term runoff) into the nearest body of water.  Rain water can, therefore, be warmed or cooled and the runoff can change the temperature of a river.

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