b'Combining high-resolution spatially distributed models withexport coefficients produced by field-scale process-oriented modelDjodjic F1, Markensten H1, Sandstrm S1, Widn Nilsson E1, Persson K, Lindsj A2, Johnsson H and Blombck K21Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, 75007 Uppsala, Sweden2Department of Soil and Environment, Swedish University of Agricultural Sciences, 75007Uppsala, SwedenIn Sweden, reduction of Phosphorus (P) losses from diffuse sources is recognized as necessary to improve water quality of impaired streams and lakes as well as the Baltic Sea. Differentmitigation measures are continuously implemented but the targeting of critical source areas at higher resolution (field and subfield scale) is still poor, mainly because of the lack of reliable tools, which would make possible targeting at resolution higher than sub-catchment. Recently, high resolution erosion maps have been developed but the corresponding tools for P losses are still lacking. In the national pollution load compilations, P export coefficients are calculated using field-scale ICECREAMDB model for the 22 regions in Sweden, 15 crops, 10 soil texturalclasses and with consideration taken to field slope and soil P content. These export coefficients are thereafter used to estimate diffuse P loads from agriculture to surrounding seas, but the highest resolution of presented results of these calculations is sub-catchment level. In this study, we combine expert coefficients together with high-resolution elevation data, soil textural distribution and measured monthly flow to estimate P loads at scales varying from cell (2mx2m) to field and catchment scale. The approach has been tested with dynamic modelling for six small agricultural catchments included in the water quality monitoring programmes with available data on water flow and nutrient concentrations. In two of the catchments exists even monitoring results at one field within each catchment. The comparisons of P loads at field and catchment scale have shown satisfactory results and model was able to capture high variation between catchments. The possibilities, limitations and potential improvements of the suggested approach are discussed. 21'