To highly accurately predict the generated power of a run-of-river type dam.

In the power plant of the run-of-river type dam, since a water storage function for preventing the flood of a downstream area is not originally provided differently from a normal dam, flow rate prediction for flood prevention is not required to begin with. Thus, without tentatively predicting a flow rate, the generated power is directly predicted. That is, the output of a neural network is defined as power generator output (power generator output difference, in this example).