Primary Causes of Thermal Pollution

Thermal pollution occurs when water bodies are degraded in terms of altering their temperatures. Commonly, it happens when people or industries undertake activities that suddenly decrease or increase the temperature of natural water bodies which may include lakes, rivers, oceans or ponds.

In today’s world, thermal pollution is a huge threat and is mainly influenced by power plants and industrial manufacturers that use water as a coolant. Urban stormwater runoff from parking lots and roads also discharges water of elevated temperatures into adjacent water bodies. When water is either used as a coolant, discharged from stormwater runoff at elevated temperatures, or released from reservoirs with unnaturally cold temperatures, it changes the natural temperature of water bodies.


On this account, the alterations of natural water resource temperatures can have dire consequences on aquatic life and local ecosystems. Here are the leading causes of thermal pollution.

1. Power, Industrial, and Manufacturing Plants

Power, production and manufacturing plants top at discharging lots of heat into nearby water resources. The operations of power generation and production emit lots of heat. So, to contain the amount of heat produced, factories and power plants draw water from the nearby water resources to maintain smooth operations after which the water is discharged back into the ocean at elevated temperatures.

Most power and production plants discharge water at 10 degrees Celsius higher than the received water temperature. As a result, it affects the aquatic lives that have become acclimatized to a habitat with a steady temperature. Furthermore, discharge of higher water temperatures decreases dissolved oxygen content in waterways resulting in the death of fish and other aquatic life. Elevated water temperatures can as well destroy the plan life along the streams, rivers, or within the lake shores that depend on stable levels of dissolved oxygen and consistent water temperatures.

2. Industrial Effluents

Industrial effluents including drainage from research institutions, hospitals, sugar manufacturing companies, explosives, and nuclear experiments emit a lot of un-utilized heat and traces of heat absorbing materials into neighboring water resources. This results in raised temperatures of the water bodies along with severe drops in the levels of dissolved oxygen. The result is the death of several fish and other aquatic life forms.

3. Domestic Sewages

Discharge of domestic sewage into lakes, rivers, streams or canals is a common phenomenon in many regions of the world. As a matter of fact, they are frequently discharged with minimal treatment or without treatment at all. Nonetheless, most people don’t know that sewage water has a higher temperature than the receiving water.

This is normally because of the organic load present in the waste water. When discharged into water, as it is predominantly the case, it alters the receiving water temperature which leads to a reduction of dissolved oxygen content and increased anaerobic conditions. Eventually, it results in death of various forms of aquatic life.

4. Urban Stormwater Runoff

During hot days and months, urban surfaces including parking lots, macadam roads, and sidewalks usually heat up by absorbing the thermal radiation from the sun. When it rains, the urban stormwater runoff absorbs the heat and discharges it into the nearby sewer systems and water bodies.

5. Deforestation

Forests and vegetation cover is responsible for reflecting back and absorbing the sun’s heat. Besides, it also cushions against the accumulation of intense heat on rivers, ponds, canals, and lakes. Thus, deforestation leaves the water sources directly exposed to sunlight and permits intense sun’s heat that would have otherwise been absorbed by trees or vegetation cover to accumulate in water sources.

Besides, atmospheric temperatures are heightened due to the thermal effect of CO2 greenhouse gases which could have been absorbed by trees. Heightened atmospheric temperatures mean compounded temperature levels of the water resources.

6. Soil Erosion

Thermal pollution can as well be realized as a result of soil erosion. This is because continued soil erosion causes siltation and sedimentation thus raising the water levels which enlarges the surface area of the water exposed to sunlight. The more the exposure to sun’s heat, the higher the water temperatures become. Streamside erosion may also remove vegetation cover along the streams further exposing the water to the sun’s thermal radiation. The high temperatures can have destructive effects on the aquatic community.

7. Hydroelectric Power Generation

Sometimes the generation of hydroelectric power leads to negative thermal loading in water resources. The power generation process, the turning of steam heated turbines, heats up the water and dumps it back into the receiving water at higher temperatures. As an outcome, it might alter the diurnal and seasonal activities as well as the metabolic responses of organisms in the water resources used to generate power.

8. Natural Causes

Geothermal activity and active volcanoes below the oceans and seas can induce natural underground heating of the water bodies. Hot rocks and active lava have the potential of heating and raising water body temperatures. The rise in temperatures merely translates to significant detrimental impacts on the marine life and the environment in general.

Photo by: Wilfredo

Sonia Madaan

Sonia is a High School Graduate and Runs the Writing and Editing Team for She is Extremely Passionate about Environment, Technology and Computing.
Sonia Madaan