1. Institute of Freshwater Ecology and Inland Fisheries Changes of agricultural diffuse nutrient inputs in major European river systems and their contribution to the nutrient loads Horst Behrendt *Institute of Freshwater Ecology and Inland Fisheries, Department of Shallow Lakes and Rivers, Mueggelseedamm 310, D-12857 Berlin, Germany Introduction Results 1.Sources of nutrient emissions into river systems 2.Longterm changes Conclusions

2. Institute of Freshwater Ecology and Inland Fisheries Investigated rivers systems in Europe* Number (>2000 km²): 450 Total area: 8,060,200 km 2 Population: 616 Million Mean specific runoff:10 - 1400 mm/(m²·a) Investigated rivers: 7 Total area: 1,625,470 km 2 (20%) Contributing countries: 3 - 18 Population: 224 Million (36%) Mean specific runoff:120 - 670 mm/(m²·a) The investigations are related to the EU-Projects EUROCAT and DANUBS or founded by NATO-CCMS or national projects

3. Institute of Freshwater Ecology and Inland Fisheries * Tonderski (1996); ** Billen & Garnier (1999) Characteristics of the investigated rivers

4. Institute of Freshwater Ecology and Inland Fisheries Applied model MONERIS Boundaries: Input to catchment soil and water, losses from soils to surface waters, riverine output from the catchment The model starts with the distributed estimation of the surplus on agri- cultural and non-agricultural areas. Long term changes for consideration of the residence time in groundwater (N) and accumulation processes (P). Distributed nutrient emissions into the surface waters of a river basin for 6 diffuse pathways and point source discharges (municipal WWTP`s and direct industrial discharges). Distributed retention coefficients for groundwater (N) and surface water.

5. Institute of Freshwater Ecology and Inland Fisheries Database: Borders of catchments and subcatchments

6. Institute of Freshwater Ecology and Inland Fisheries Mineral Fertilizer Lifestock Crop Yields Database: Statistical data e.g. for agriculture

7. Institute of Freshwater Ecology and Inland Fisheries Nutrient emissions into the river systems

8. Institute of Freshwater Ecology and Inland Fisheries Contribution of pathwas to the total emissions into the river systems N-emissions for Period Rhine 1998-2000 Elbe1998-2000 Po1991-1995 Vistula1996-2000 Oder1993-1997 Danube1998-2000

9. Institute of Freshwater Ecology and Inland Fisheries Contribution of different human sources and natural background to the N-emissions in the Danube basin

10. Institute of Freshwater Ecology and Inland Fisheries Regional differences of the agricultural N- emissions in European river systems

11. Institute of Freshwater Ecology and Inland Fisheries Regional differences of the agricultural P- emissions in European river systems

12. Institute of Freshwater Ecology and Inland Fisheries Identification of intensities of processes Intensity of N-retention in unsaturated zone and in groundwater

13. Institute of Freshwater Ecology and Inland Fisheries Intensities of retention processes in terrestric and aquatic spheres

14. Institute of Freshwater Ecology and Inland Fisheries Total emissions surface water retention and load N P Spec. N-fluxes (kg/ha) Spec. P-fluxes (kg/ha) If the retention in surface waters is not included in the model, the load and the source estimation can completely fail.

15. Institute of Freshwater Ecology and Inland Fisheries Longterm changes of nutrient emissions and loads

16. Institute of Freshwater Ecology and Inland Fisheries Longterm changes of observed and calculated nutrient loads for the Odra at Krajnik Dolny For nitrogen the human induced changes are overlayed by flow changes The TP load shows a clear decrease since mid 1980s

17. Institute of Freshwater Ecology and Inland Fisheries Longterm changes of DIN and TP load calculated based on observed flow, longterm average flow and without Iron Gate.

18. Institute of Freshwater Ecology and Inland Fisheries Changes of nutrient emissions by human activities and natural background in the Odra The reduction of N emissions is mainly due to reduction of agricultural & urban discharges The reduction of P emissions is only due to reduction of urban discharges

19. Institute of Freshwater Ecology and Inland Fisheries Changes of nutrient emissions by human activities and natural background in the Danube The longterm changes of the sources in the Danube are similar than in the Odra. But the reduction of N and P emissions is lower

20. Institute of Freshwater Ecology and Inland Fisheries Results of Scenario calculation

21. Institute of Freshwater Ecology and Inland Fisheries Efficiency of different measures to change the situation in the Elbe river system Only the introduction of a taxis on mineral N-fertilizer (Ntaxis) leads to a clear reduction of the agricultural N- emissions For a set of maximum reduction measures the total N-emissions will be remain about 400% above the geogenic background.

22. Institute of Freshwater Ecology and Inland Fisheries A substantial reduction of agricultural N emis- sions is only possible for SC4, which assumes a reduction of meat consumption to 0.1 AU per inhabitant Efficiency of measures to change the situation in the Danube Agricultural P sources can be effectively reduced by management of arable land without ploughing

23. Institute of Freshwater Ecology and Inland Fisheries Agricultural inputs (N) and point sources (P) are the dominant source of nutrient loads in the most of the investigated river basins. A gradient exists from west to east. The N and P emissions and loads into Eastern European rivers are increased from the 1950s to the 1980s by a factor of 2 to 3. A substantial decrease was found for P loads in the 1990s. The reduction of N loads is often overlayed by flow variation. The consideration of the retention of matter in the surface waters is of similar importance for the modelling of loads as the the estimation of sources and pathways. MONERIS can be applied for the estimation of the nutrient emissions and loads in the European river systems Conclusions

24. Institute of Freshwater Ecology and Inland Fisheries Results VI: Nutrient loads within subcatchments & for river outlet Observed and calculated loads (MONERIS) of TP and DIN for the tributaries of the Danube Deviation between observed and calculated loads for the different river systems