抄録
Environmental flow is necessary to keep the river environment in good condition. It should be considered as one of the objectives of river engineering works as well as flood protection and water resources. In this paper environmental flow is evaluated by environmental economics. Cost is calculated from the loss of hydropower stations which supply environmental flow. In the Tonegawa River basin, it costs over ten billion yen each year. CVM is used to evaluate the benefit. The survey was performed at the Naramata Dam in the Tonegawa River basin. The number of the sample was rather small, but a reasonable result came out. The benefit calculated is around 11, 000 yen each year for one family. Then the Input-Output Analysis was carried out to evaluate the impact of the environmental flow. In the Kanto region, the total impact amounts to 42 billion yen.
