Abstract. There will be studied modeling the water resources contamination level in open nodes. The mathematical formulation of the problem of calculating unsteady flows in an arbitrary system of river channels based on one-dimensional equations of the SaintVenant type is given in this work. Wastewater in the basin is controlled by six indicators: BOD, petroleum products, suspended solids, total phosphorus and nitrogen, as well as iron. Four cleaning methods are considered: mechanical, chemical, biological and biochemical. In the calculation process, each of these methods of wastewater treatment can be compared with the rest.