Zoning methodology and application to China’s watersheds for water pollution control

The existing methods for watershed zoning have tended to be very subjective in China. This is especially true for the zoning of the water pollution control-unit, resulting from the lack of unified zoning methodologies and regulations.Aiming at this problem, a three-level zoning system or the watershed-control regions-control units system is proposed in the study.The system adopts a combined approach of qualitative and quantitative methods for the zoning study of watershed pollution control.An Analytic Hierarchy Process (AHP) model will be constructed at the control-unit level, which is the central piece of the system.Based on four factors, i.e. catchment characteristics, urban distribution, industrial distribution and agricultural distribution, a watershed is divided into various control units according to the main direction of various discharge sources.The system is applied to the Songhua River watershed as a study case.The whole watershed is ultimately divided into three control regions and thirty-three control-units.It is noted that ten counties including Morin Dawa Daur Autonomous Banner, are divided into two or more control units.The proposed system for the zoning study of watershed pollution control in China is based on the nature of basin catchments and fully embodies the focus and direction for the management of watershed pollution control.It sets up the implementing targets and spells out the responsibilities and missions for local governments.It thus could provide the basis and guarantee for scientifically planning and implementing watershed pollution control plans in China.