The contamination of cold water by warm water. Sources of heat include water used for cooling in electricity stations, the urban heat island, and the construction of reservoirs. That warmer temperatures lower dissolved oxygen in the water, increase respiration rates of organisms, and increase fish and wildlife susceptibility to disease, parasites, and toxic chemicals is generally agreed; see B. Phillips, ed. (2001) on thermal pollution in the Murray-Darling Basin Waterways.

Interestingly, Beser’s 2007 paper (Digital Repository U. Maryland), in a study of the effects of the thermal effluent in Chesapeake Bay, finds that thermal effluent does ‘not cause diversity differences between submersed aquatic macrophyte communities in different areas of the thermal regime’.