The article is devoted to the development of a mathematical model of atmospheric dynamics and the spread of environmentally harmful impurities over the city, taking into account the influence of the river that does not freeze in the winter. The article describes a mathematical model for calculating the dynamics of the atmosphere and the distribution of harmful outcomes and model testing results by the example of several tests. . Also shown is the result of a model calculation of the spread of harmful impurities directly above the city of Krasnoyarsk.