[Catchment scale risk assessment and critical source area identification of agricultural phosphorus loss]

Agricultural non-point source phosphorus pollution is a severe problem for rural water bodies in China, but hard to control directly because of its special characteristics. In this paper, an approach on the catchment scale risk assessment and critical source area identification of agricultural phosphorus loss in northern China was made, based on the catchment scale phosphorus ranking scheme and the method proposed by Gburek et al. Eight factors were selected and weighed in the modified catchment scale phosphorus ranking scheme, and the phosphorus loss risk rating of each factor was adjusted based on the current professional standards and the actual circumstances in China. The areas with ' high' risk rating of phosphorus loss in definite catchment were the critical source areas for non-point source phosphorous pollution control in that catment. The availability of obtained data and the quantification of the assessment were taken into account in the new scheme, and GIS technique and geostatistics were used for confirming the factors. Therefore, the new scheme had definite operability and practicability.