Any natural object with a temperature higher than the absolute zero is a source of infrared radiation. Thermovision (infrared mapping) is applied to detect, record, process and image this radiation. This technique is used, among others, in the industry, power and construction sectors, military applications and scientific research. It is also used for the determination of the surface water temperature distribution in artificially heated bodies of water. The authors discuss this technique using the example of five Konin lakes whose chain is incorporated into the cooling system of the Pątnów and Konin power plants.