Thermal pollution of water bodies is an inevitable consequence of a power plant operation. To minimize the harmful effects, it is necessary to evaluate the different locations for the heated water discharge from the power plant. The most effective approach to solving these problems is a computational experiment. In this paper, the numerical studies of thermal pollution of the Irtysh River as a natural water cooling system from the power plant operation were presented. And studies were conducted to study thermal pollution under different scenarios, the impact of the heated water discharge from a power plant into the Irtysh River.