Integrated assessment on nutrient emission and export from watersheds of China based on computer simulation technology

In this study, we developed a framework of an integrated assessment system for analyzing nutrient emission and export from watersheds of China. This system integrates modules of different methods and levels of scale. It consists of three major sub-modules: Emission model of agricultural diffuse source of nutrients (EMADS); Emission model of non-agricultural sources of nutrients (EMNAS); Estimation model of nutrient export from watersheds of China (EMNEW). EMADS is a complex adaptive model. It links changes in agricultural policies, the rural socio- economic development, and agricultural diffuse sources of nutrient emissions. EMNAS is a system dynamics model, which is a platform for integrating different levels of models and used to estimate industrial and domestic point sources of nutrients, natural diffuse source of nutrients and kinds of sinks. EMNEW is an indigenous version of NEWS model. This integrated system aims to analyze mechanism of nutrient export from Chinese watersheds driven by both natural and socio-economic factors, to explore the possible future trends in nutrient export, and to develop management strategies for integrated watershed management on nutrients and coastal eutrophication prevention and control.