Assessment of Nitrogen and Phosphorus Environmental Pressure at European Scale

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In surface water bodies, the increase in nutrient concentration above the natural background levels enhances the productivity, causing the phenomenon of eutrophication (Nixon, 1995). The euthrophication has been identified as a major cause of impaired water quality of rivers, lakes and estuaries (EEA, 2001; EEA, 1999; Carpenter et al. 1998; Meybeck, 1982). Agriculture is considered the main responsible for nitrogen enrichment in water bodies (Kronvang et al. 1995; Larsen et al. 1999), while in the case of phosphorus, the households and industry wastewater discharges and the soil erosion are the principal sources of pollution (EEA, 2001, Follett and Hatfield 2001).

In order to cope with the increase of nutrients from agriculture and point sources, in 1991 the European Economic Community adopted the so called Nitrate Directive (91/676/EEC) and the Urban Waste Water Treatment Directive (91/271/EEC). In 2000, the European Commission adopted the Water Framework Directive 2000/60/EC (CEC, 2000) to establish a framework for the Community action in the field of water policy. With the WFD the water quality issue is tackled in a comprehensive way, integrating the previous regulations. The directive aims at protecting and enhancing the status of water resources and promotes a sustainable water use based on a long-term protection of the available water resources. In order to achieve these goals by 2015, the WFD plans a series of actions that the Member States have to implement at the hydrologic river basin level according to a tight schedule. By the end of 2009 Member State shall establish River Basin Management Plans which include the results of the analysis of pressure and impact (performed in 2005), the Monitoring Program (before 2007), the mitigation strategies implemented in the Program of Measures (before 2009), a summary of the public information and consultation measures taken and a list of competent authorities. The enforcement of the WFD raises new challenges for the research community and models have been identified as the tools that can contribute to fulfil the requirements stated in the policy framework (Horn et al., 2004; EUROHARP, 2005; GD IMPRESS). The WFD asks for an assessment of the present pressures and the evaluation of implications of the plan of measures. In the case of nitrogen and phosphorus pollution, this involves the analysis of the role of the different sources (point and diffuse) in the nutrient export from the river basin. The estimation of the contribution of different sources to the pollution is called source apportionment.

Studies on source apportionment were performed mostly in North and Western Europe, while scarce information is available for Mediterranean and West-European countries (EEA, 2005). In addition, the available estimations are based on approaches that are targeted on specific spatial scales and water body types (EEA, 2005).

The objective of this study was the development and the implementation of a modelling approach to estimate the nitrogen and phosphorus pressures at the European scale. Inparticular the work aimed at quantifying the nutrient diffuse emissions to the surface waters and the contribution of the different nutrient sources to the in-stream total load.
In this study, the estimation of nutrient pressures was performed by means of the model GREEN, Geospatial Regression Equation for European Nutrient Losses (Grizzetti, 2006). GREEN is a simplified conceptual model which relates the nutrient loads to spatially referenced nutrient sources and basin characteristics. It was inspired from the SPARROW model (Smith et al., 1997) modified to be applied in Europe.

The GREEN model was developed at the European Commission’s Joint Research Centre (Institute for Environment and Sustainability, Rural, Water and Ecosystem Resources Unit) in the context of the project FATE (Fate of Agrochemical in Terrestrial Ecosystems, Bouraoui et al., 2006), a wider modelling approach to address the problem of nutrient in the environment. The main concept of FATE is that the processes responsible for the nutrients fate are studied at the relevant scale, making best use of readily available data at European level. The FATE modelling approach is structured in three tiers:

1. the statistical approach for the European scale GREEN (Grizzetti, 2006), used as a screening tool to identify catchments with high nutrient losses that can cause a threat to water bodies;

2. the semi-distributed, physically-based SWAT model (Arnold et al., 1998) to understand within those areas, the major processes and pathways determining the nutrient losses;

3. the farm-scale EPIC model (William, 1995) to elaborate appropriate farming practices that could reduce pollution load without endangering the farm economic sustainability.

The implementation of modelling tools relies on data availability. In the context of the FATE project, harmonised European wide data layers were collected or built with the specific objective of implementing the FATE tiered modelling approach. An overview of the data used in the FATE project is given by Mulligan et al. (2006). This report describes the analysis of nutrient pressure at the European scale carried out by the GREEN model (FATE modelling tier 1). The application of the entire FATE modelling approach is described in Bouraoui et al. (2006). The work presented in this report is based on the PhD thesis of Grizzetti (2006), where the model development is described in details, but the results refer to the model application using a different data set for nutrient inputs from agriculture, which was developed subsequently within the FATE project (Grizzetti et al., 2006).

In this report, after the description of the model structure (Chapter 2) and the data collected and developed for the study (Chapter 3), the calibration of the model in 7 large European river basins (part of the Danube, the Rhine, the Elbe, the Weser, the Ems, the Seine, the RhĂ´ne and the Meuse) is presented (Chapter 4). Finally, the analysis of
nutrient pressures in the 7 large European river basins (Chapter 5) and the extrapolation
at the European scale (Chapter 6) are presented and discussed.

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