Abstract: This paper presents the results of model calculations of the behavior of the ionosphere during a complex space-weather event that occurred in September 2017. The main attention is paid to the analysis of the response of an integral characteristic of the ionosphere—global electron content (GEC)—to geomagnetic storms on September 7–8. Comparison of the temporal behavior of the model and experimental GEC showed there to be a good qualitative agreement between the temporal variations of hydroelectric power stations associated with geomagnetic storms. At the same time, the absence in the results of model calculations of positive hydroelectric disturbances observed on September 7, 8, and 11 is noted. It is hypothesized that these positive disturbances of the GEC on the indicated days may be associated with the observed solar-proton events and precipitation of protons from the magnetosphere, but not taken into account in model calculations.