Thermal pollution is defined as sudden increase or decrease in temperature of a natural body of water which may be ocean, lake, river or pond by human influence. This normally occurs when a plant or facility takes in water from a natural resource and puts it back with an altered temperature. Usually, these facilities use it as a cooling method for their machinery or to help better produce their products. - See more at: http://www.conserve-energy-future.com/causes-and-effects-of-thermal-pollution.php#sthash.j1VbXJJa.dpuf