In the search for tools for evaluating the effects of national action plans combating diffuse nutrient pollution causing eutrophication of surface waters, a study of the nitrogen (N) flow in 17 Danish agricultural catchments was carried out. Data on N input and N harvest for the agricultural year of 1993/1994 was obtained from questionnaire surveys facilitating the set up of N balances. Net export of N from the catchments measured at the outlet was obtained from time-series of stream water chemistry and discharge from 1993-1997. N leaching from the root zone of each field was calculated using an empirical model. A physically based lumped rainfall-runoff model was used for separating the hydrograph time-series into three runoff components: baseflow, interflow and overland flow. Large regional variations in net N input were found ranging from 62 kg N ha−1 yr−1 in the loamy eastern part of the country dominated by cereal production to 137 kg N ha−1 yr−1 in the western part characterised by less fertile sandy soils and dominated by animal husbandry. N leaching from the root zone showed a corresponding variation with regional averages ranging from 34.5 kg N ha−1 yr−1 to 90.9 kg N ha−1 yr−1. No similar regional pattern could however be found regarding net N export, and no relationship could be established between net N export and root zone N leaching. This finding was ascribed to a varying and in some catchments very high (>80%) N retention during subsurface transport to the stream. The hydrological modelling revealed that loamy catchments had a high proportion of quick flow (overland flow + interflow), whereas baseflow dominated the sandy catchments. Further, a highly significant relationship between N retention and proportion of quick flow was found emphasising the importance of understanding the hydrological pathways. This should be taken into consideration when evaluating the N loading of surface waters resulting from a given agricultural practice and the effects of possible changes in this practice.
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Research Article|
October 01 2001
Analysis of the hydrology and flow of nitrogen in 17 Danish catchments
H. E. Andersen;
H. E. Andersen
1National Environmental Research Institute, Department of Streams and Riparian Areas, Vejlsøvej 25, DK-8600 Silkeborg, Denmark
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M. L. Pedersen;
M. L. Pedersen
1National Environmental Research Institute, Department of Streams and Riparian Areas, Vejlsøvej 25, DK-8600 Silkeborg, Denmark
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O. Jorgensen;
O. Jorgensen
1National Environmental Research Institute, Department of Streams and Riparian Areas, Vejlsøvej 25, DK-8600 Silkeborg, Denmark
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B. Kronvang
B. Kronvang
1National Environmental Research Institute, Department of Streams and Riparian Areas, Vejlsøvej 25, DK-8600 Silkeborg, Denmark
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Water Sci Technol (2001) 44 (7): 63–68.
Citation
H. E. Andersen, M. L. Pedersen, O. Jorgensen, B. Kronvang; Analysis of the hydrology and flow of nitrogen in 17 Danish catchments. Water Sci Technol 1 October 2001; 44 (7): 63–68. doi: https://doi.org/10.2166/wst.2001.0390
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