Evaluation of effects of dams on river ecosystem service functions in China

River ecosystem service functions imply the natural environmental conditions and their effectiveness formed and sustained by river ecosystem and its ecological processes. River ecosystem service functions were divided into two groups by their types and effectiveness : river ecosystem products and river ecosystem services. River ecosystem products consist of the products and services harvested firsthand from river ecosystem, including water supply, fish resources, inland navigation, hydropower, recreation and cultural, and raw materials. River ecosystem services are functions to sustain the natural environmental conditions and ecological processes which are necessary for the human survival, including flooding control, soil and sand transfer, water resource storage, soil conservancy, environmental purification, nutrient cycling, and providing wildlife habitat. The accurate valuation of effects of dams on river ecosystem service functions is very important to environmental impact assessment of water conservancy