GREEN
Source: Commission modelling inventory and knowledge management system (MIDAS)
Date of Report Generation: Thu Mar 06 2025
Dissemination: Public
© European Union, 2025
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Overview
Acronym
GREEN
Full title
Geospatial Regression Equation for European Nutrient losses
Main purpose
A statistical model used to assess the impact of different nutrient sources, i.e. agriculture, wastewater and industrial discharges, atmospheric deposition, on freshwater and coastal waters.
Summary
GREEN is a statistical model used to assess the impact of agricultural fertilizers and other sources of nutrients on the environment. The GREEN model estimates the mass discharge of total nitrogen (N) and total phosphorus (P) through the stream network down to marine coastal areas, the concentration of N and P, and the relative contribution of diffuse and point sources to the total mass discharge/concentration.
GREEN is a simplified conceptual model, which distinguishes between two different pathways in nutrient transfer from sources to catchment outlet (Grizzetti et al., 2006, 2005a, 2005b). Diffuse sources (DS), which include applied synthetic and manure fertilisers, atmospheric deposition and emissions with wastewater from scattered dwellings (i.e. homesteads that are disconnected from sewerage systems), first undergo degradation in the soil via various processes including crop uptake, atmospheric losses and soil storage, before reaching the stream network. Point sources (PS), which include discharges from sewers, waste water treatment plants, industries and paved areas are directly emitted to the stream network. Once in the stream network, nutrients are partially retained in the streams due to algae growth, atmospheric losses etc. The calculation is performed on a catchment of interest, which is subdivided into a number of sub-basins (n) based on a topographic discretisation. A routing structure is then elaborated and serves to establish an emitting-receiving sub-basins relationship, i.e. an up-stream nutrient load is considered as an additional point source to the receiving down-stream sub-basin. With this representation, the emissions of N and P from upstream are transferred downstream taking into account the mass fraction lost in the basin and in the stream network.
Model categories
Οther
Model keywords
Environmentagriculturewaternitrogenwastewaterphosphorus
Model homepage
Ownership and Licence
Ownership
EU ownership (European Commission)
Ownership details
Licence type
Free Software licence
The license grants freedom to run the programme for any purpose; freedom to run the program for any purpose; freedom to study (by accessing the source code) how the program works, and change it so it does enable computing; freedom to redistribute copies; and freedom to distribute copies of modified versions to others.
Details
Structure and approach
Input and parametrization
Model inputs are:
- Annual climate data (precipitation)
- Annual input of fertilizer application (manure, mineral fertilizers), atmospheric nitrogen deposition and biological fixation, extent of agricultural and non-agricultural area.
- Discharges of N and P from industrial installations, untreated and treated wastewater. The latter are usually estimated from population density and connectivity to waste water collecting and treating systems, or available datasets of wastewater discharge points (Vigiak et al. 2018; 2020; 2023). Geomorphological information is needed in order to build the hydrographic model used in the calculation. The model consists of a set of interconnected sub-basins each containing a segment of the stream network.
Main output
Model outputs are:
- Nitrogen and phosphorus source apportionment
- Annual discharge of nitrogen and phosphorus loads, and concentration in stream water.
Spatial & Temporal extent
The output has the following spatial-temporal resolution and extent:
| Parameter | Description |
|---|---|
| Spatial extent / country coverage | EU Member states 27NorwaySwitzerland |
| Spatial resolution | Other |
| sub-catchment | |
| Temporal extent | Long-term (more than 15 years) |
| The latest model application provides annual outputs for 1990-2018. | |
| Temporal resolution | Years |
Quality & Transparency
Quality
Model uncertainties
Models are by definition affected by uncertainties (in input data, input parameters, scenario definitions, etc.). Have the model uncertainties been quantified? Are uncertainties accounted for in your simulations?
- response
- no
- details
- The model is occasionally calibrated depending on the availability of data. Calibration provides an indication of the error associated to the model in predicting loads and concentrations.
- url
Sensitivity analysis
Sensitivity analysis helps identifying the uncertain inputs mostly responsible for the uncertainty in the model responses. Has the model undergone sensitivity analysis?
- response
- no
- details
- The model, insofar as spatially distributed, is sensitive to the input emissions. Sensitivity analysis is only carried out for model parameters, and not on data inputs.
- url
Have model results been published in peer-reviewed articles?
- response
- yes
- details
- url
Has the model formally undergone scientific review by a panel of international experts?
Please note that this does not refer to the cases when model results were validated by stakeholders.
- response
- no
- details
- Only in the context of the scientific peer review of journal papers.
- url
Model validation
Has model validation been done? Have model predictions been confronted with observed data (ex-post)?
- response
- yes
- details
- The model has been extensively compared with measured N and P concentration data and to other model outputs, as documented in the references provided.
- url
Transparency
To what extent do input data come from publicly available sources?
This may include sources accessible upon subscription and/or payment
- response
- Entirely based on publicly available sources
Is the full model database as such available to external users?
Whether or not it implies a specific procedure or a fee
- response
- no
- details
- (To be made available with the latest release)
- url
Have model results been presented in publicly available reports?
Note this excludes IA reports.
- response
- yes
- details
- documents
For details please refer to the 'peer review for model validation' documents in the bibliographic references
Have output datasets been made publicly available?
Note this could also imply a specific procedure or a fee.
Is there any user friendly interface presenting model results that is accessible to the public?
For instance: Dashboard, interactive interfaces...
- response
- yes
Has the model been documented in a publicly available dedicated report or a manual?
Note this excludes IA reports.
- response
- yes
- details
- The model does not require a user’s manual. A full description of the model can be found in Grizzetti et al. (2021). The R implementation package includes a vignette that can be used for guidance.
Is there a dedicated public website where information about the model is provided?
- response
- no
- details
- url
Is the model code open-source?
- response
- yes
Can the code be accessed upon request?
- response
- not applicable
- details
The model’s policy relevance and intended role in the policy cycle
The model is designed to contribute to the following policy areas
- Agriculture and rural development
- Environment
The model is designed to contribute to the following phases of the policy cycle
- Evaluation – such as ex-post evaluation
- Formulation – such as ex-ante Impact Assessments
The model’s potential
Appraisal of policy scenarios in terms of mass discharges and concentrations of N and P, by identifying areas that might be affected by nutrient pollution , evaluating the effectiveness of the legislation and policy options in reducing nutrient loads entering freshwaters.
Previous use of the model in ex-ante impact assessments of the European Commission
Use of the model in ex-ante impact assessments since July 2017.
2022SWD/2022/541 final
Impact Assessment accompanying the document Proposal for a Directive of the European Parliament and of the Council concerning urban wastewater treatment (recast)
- Lead by
- ENV
- Run by
- European Commission
- Contribution role
- baseline and assessment of policy options
- Contribution details
GREEN was used to compute the discharges of N and P to the EU regional seas taking into account also other sources of nutrients (agriculture, atmospheric deposition etc.). Users can run GREEN to replicate the results of its contribution to this impact assessment and compare the different scenarios using this <a href="https://green.geodab.org/" target="_blank" rel="nofollow" />web application</a>.