Materials accounting as a policy tool for nutrient management in the Danube Basin

Nutrient management has to consider both: Nutrients as essential elements f or the biosphere with limited resources and nutrients as potential environm ental pollutants (eutrophication, groundwater-deterioration). Materials Acc ounting techniques enable to describe and quantify the metabolism of Nitrog en and phosphorus in large river Basins, such as the Danube Basin. By knowi ng the sources and pathways of nutrients it is possible (i) to identify the key causes of pollution problems and (ii) to point out inefficient use of the limited resource "nutrients". Additionally, it is possible to design ef ficient measures based on nutrient balances. Materials Accounting observes the changes of stocks within a time interval. Therefore, it allows the earl y recognition of the accumulation and depletion of harmful substances (e.g. Nitrate in the groundwater) or of limited resources (e.g. P in topsoils) i n the environment. In combination with scenario development Materials Accou nting has a high predictive power. There isa substantial difference in desi gning the most efficient measures for reducing nutrient inputs or to optimi se the use of limited resources in the entire Danube Basin and in individua l countries. (C) 1999 Published by Elsevier Science Ltd on behalf of the IA WQ. All rights reserved.