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Causes and Effects of Thermal Pollution

Causes and Effects of Thermal Pollution 

Thermal Pollution

  • Thermal pollution is the degradation of water quality by any process that changes the water temperature.
  • In other words, thermal pollution is defined as an increase or decrease in the temperature of a natural body of water like ocean, lake, river or pond by human influence.

Causes of Thermal Pollution

Water as a Cooling Agent in Power, Manufacturing and Industrial Plants

  • Production and thermal plants are the biggest sources of thermal pollution.
  • These plants draw water from the nearby sources to keep machines cool and then release the water back to the source with higher temperature.
  • Water with high temperature has less capacity to hold oxygen and thus many aquatic species find it difficult to survive.

Soil Erosion

  • Soil erosion is another major factor that causes thermal pollution.
  • Consistent soil erosion causes water bodies to rise, making them more exposed to sunlight.


  • Trees and plants prevent sunlight from falling directly on lakes, ponds or rivers.
  • When deforestation takes place, these water bodies are directly exposed to sunlight, thus absorbing more heat and raising their temperature.

Runoff from Paved Surfaces

  • Urban runoff discharged to surface waters from paved surfaces like roads and parking lots can make water warmer.
  • During summer seasons, the pavements get quite hot, which create warm runoff that get into the sewer systems and water bodies.

Natural Causes

  • Natural causes like volcanoes and geothermal activity under the oceans and seas can trigger warm lava to raise the temperature of water bodies.
  • Lightning can also introduce massive amount of heat into the oceans.                Causes and Effects of Thermal Pollution

Effects of Thermal Pollution

Decrease in DO Levels

  • The warm temperature reduces the levels of DO in water. Warm water holds relatively less oxygen than cold water.
  • The decrease in DO can create suffocation to animals such as fish, amphibians and copepods, which may give rise to anaerobic conditions.
  • Warm water allows algae to flourish on the surface of water and over the long term, the growing algae can decrease the penetration of sunlight and photosynthesis in the water body.
  • Many aquatic species are sensitive to small temperature changes such as 10 Celsius that can cause significant changes in an organism’s metabolism and other adverse cellular biology effects.

Increase in Toxins

  • With the constant flow of high temperature discharge from industries, there is a huge increase of toxins in the natural body of water.

Change in Biodiversity

  • Changes in the environment may cause certain species of organisms to shift their base to some other place, while there could be significant number of species that may shift inside because of warmer waters.

Affects Reproductive Systems

  • Excessive temperature can cause the release of immature eggs or can prevent the normal development of certain eggs.

Increases Metabolic Rate

  • Thermal pollution increases the metabolic rate of organisms as increasing enzyme activity that occurs makes the organisms to consume more food than what is normally required, if their environment were not changed.                            Causes and Effects of Thermal Pollution
  • It disrupts the stability of food chain and alters the balance of species composition.


Environment & Biodiversity

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