Thermal pollution is a form of water pollution characterized by the degradation of water quality due to the rise or fall in the temperature of certain water body.
Thermal pollution of water bodies is almost always caused by humans, and is mostly the result of use of water as a coolant in power plants and different industrial facilities.
Unlike chemical pollution of water, thermal pollution primarily results in a change in the physical properties of water.
Thermal water pollution can cause huge damage to many aquatic ecosystems because there are many fish and other aquatic organisms that have adapted to particular temperature of the water and once this temperature changes they often fail to adapt and die in the process as a result of thermal shock.
Thermal water pollution is mostly associated with elevated water temperatures. The higher temperatures of water cause oxygen level to decrease and this can lead to major decline of fish species. The higher water temperatures can also lead to increased bacteria levels.
The less common is the case of thermal pollution by the release of very cold water from the base of reservoirs and into warmer water bodies such as rivers.
Thermal water pollution can lead to reduced biodiversity of the affected area and cause migration of many fish species.
Even small temperature changes of one to two degrees Celsius can cause significant changes to many aquatic species and lead to loss in biodiversity.
Thermal pollution can in some very rare cases have beneficial effect and may even lead to positive impact on certain aquatic species such as manatee.
More than 75% of thermal pollution in United States is attributed to power plants.
In order to control the levels of thermal pollution many industrial facilities in developed world are equipped with cooling ponds and cooling towers.
Urban runoff from roads and parking lots can also become major source of thermal pollution, particularly during warm weather.
Thermal pollution of water can also lead to increased levels of chemical pollution because toxicity of many harmful chemicals often increases with the increase in temperature.
One of the best ways to reduce thermal pollution is to primarily focus on energy facilities that do not have large water requirements for cooling purposes.