Determinants of Phosphorus Levels in Danish Watercourses, Lakes, Coastal Waters and Oceans, 1989-2004

K.H. Tiedemann (Canada)


Time-series models, least squares estimation, phosphorus contamination, phosphorus levels in surface water, agricultural management.


Excessive use of natural and artificial fertilizers can lead to phosphorus contamination of surface waters, with potential implications for human and animal health and for the environment. Although not implicated in damage to human health at typical availability, excessive levels of phosphorus can contribute to eutrophication in surface waters. This study provides an analysis of the determinants of phosphorus levels in Danish watercourses, lakes, coastal waters and ocean waters, and it examines the impact of Danish agricultural management policies on these phosphorus levels. Statistical modeling, using ordinary least squares, forms the framework for the analysis. The study has four main findings. First, the Danish Government has used a variety of measures to reduce phosphorus balance in agriculture, including reduced use of natural and man made fertilizers to meet the targeted reduction in phosphorus loadings of eighty percent or 8,050 tonnes P per year. Second, phosphorus balances or inputs have fallen from 15.0 kg/ha in 1989-1992, to 12.0 kg/ha in 1993-1996, to 10.5 kg/ha in 1997-2000 and to 9.5 kg/ha in 2001-2004. Third, phosphorus concentration levels in watercourses have fallen from 0.45 mg/l in 1989 1992, to 0.20 mg/l in 1993-1996, to 0.17 mg/l in 1997 2000 and to 0.16 mg/l in 2001 -2004 and in lakes have fallen from 0.11 mg/l in 1989-1992, to 0.088 mg/l in 1993-1996, to 0.078 mg/l in 1997-2000 and to 0.095 mg/l in 2001-2004. Fourth, agriculture net phosphorus balances in watercourses, lakes, coastal waters and ocean waters are significantly driven by phosphorus loadings in agricultural soil and by precipitation runoff.

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