The authors propose the simulation models of river flow management during extreme river discharges for а hydro complex with a hydroelectric power plant (HPP) on a main river and a flood control facility on its side tributary, including the case of their joint operation as part of a system of flood control facilities distributed on a drainage basin. The possibility of applying the previous years’ watermanagement plans for the choice of flood control facilities locations is considered. In the mathematical model of a hydro complex, operating modes of a HPP are assigned using its reservoir operating rule curves, considering the requirements of safety and environmental protection. In the mathematical model of a flood control facility, the scheme for flood discharge through uncontrolled bottom spillways and an uncontrolled surface spillway is considered. The use of the models makes possible to determine the operating modes of hydro facilities, considering the modern economic and environmental requirements, revision of their parameters, estimation of the energy-economic and environmental effects from the creation of systems of flood control facilities distributed on drainage basins.