b'A nitrogen emission map for catchments based on streammeasurements used to calculate nitrogen emissions from agricultural areas in three small Danish catchmentsVant Veen SGW1, Kjeldgaard A1, Tornbjerg H1, Windolf J1, Blicher-Mathiesen G1 and Kronvang B11Aarhus University, Department of Bioscience, DK-8600, Silkeborg, DenmarkThis study investigates the possibility to establish a local nitrogen emission map based on stream measurements. Nitrogen emissions from agricultural areas in three different Danish pilot catchments (200-1200 ha) have been determined by intensive daily monitoring of discharge and total nitrogen concentrations at a main gauging station and several synchronously monitoring stations placed within the catchment. The nitrogen emissions from agricultural areas werecalculated utilizing a source apportionment taking into account nitrogen retention in surfacewater. The emission of nitrogen from agricultural areas within the sub-catchments was also used to investigate the local groundwater retention of nitrogen, which was compared to thegroundwater retention from the Danish National Nitrogen Model. The different uncertainties involved in calculating sub-catchment nitrogen emission maps and retention in groundwater is discussed. The nitrogen emission and retention maps were calculated based on two years of intensivemeasurement data from the three catchments covering different landscape types in Denmark. The outcome reveals that nitrogen emission varies a lot between the different catchments and within each catchment. Moreover, we found that the local groundwater retention in the sub-catchments in two of the pilot catchments showed large variations and was different as compared to the national mapping of nitrogen retention. Our study shows that measurements of nitrogen emissions in streams provide a goodopportunity for developing local nitrogen emission maps for agricultural areas. The map can give an overall picture of the spatial variability of the nitrogen loadings from agricultural areas within each sub-catchment and between the sub-catchments. This means, that the map can be used to get an overview of the local hot spot nitrogen emission areas which can be a help in order to better choose targeted mitigation measures. Acknowledgements: This study is funded by a grant from the GUDP in Denmark.3'