[Main sources of urban non-point source pollution and control measures for classified catchments].

The change of land use and management practices is one of the most important factors that affecting water quality, proper land use management practices can improve water quality in a watershed. A stepwise regression model was used for finding the relationship between lake water quality and urban land use types, and rural residential, urban residential, commercial land and bottomland were determined as the main sources of non-point source pollution (NPS). The 17 catchments in the study area were clustered into 3 groups through land use types, representing rural residential, urban residential, commercial land and bottomland separately. According to the different characters of landscape structures in each group, appropriate countermeasures designed for effective NPS control simplified the practices and improved the maneuverability of urban NPS control.