Flanders places nitrogen models together under one shell

Monday, 1 December 2014

In support of the Integrated Approach to Nitrogen (PAS) in Flanders, the Flemish nitrogen dispersion models VLOPS and IFDM will be brought under one user interface. Analogous to AERIUS, this instrument may be used to support both the development of policy and the issuing of permits. The decision was made in a series of meetings of the Flemish PAS model working group during which the AERIUS team shared Dutch experiences and knowledge.

Jan Verheeke is the independent chairman of the model working group. He explains that the choice of models was made by looking at the requirements of the Flemish PAS. ‘Calculations for the issuing of permits must be consistent with those that are used for policy-making, monitoring and possibly for taking corrective action. The instrument, therefore, must be able to calculate on individual company level as well as on national level. This idea was inspired by the way the Dutch PAS works, using AERIUS support.’

In order to create the desired instrument, Flanders will join two existing nitrogen models under one shell. The first model is IFDM, which is good at calculating short-distance dispersion. It can also calculate line sources and contains a module on the influence of buildings.  VLOPS is the second model; this is the Flemish implementation of the OPS model that also forms the calculation centre of AERIUS. This second model is used particularly to calculate nitrogen dispersion over long distances, but it is also good at calculating short distances.

Verheeke continues: ‘Another important requirement for our new instrument is that it should be able to work in collaboration with AERIUS. After all, certain economic activities in Belgium cause nitrogen deposition in the Netherlands and vice versa.  Therefore, it is important for both the Dutch and Belgian PAS to have insight into emissions and deposition in the neighbouring country. At the very least, this requires harmonisation of calculation tools.’

Legal guarantee of the PAS is a third major point of attention for the Flemish. The margin of error that is common in the world of computer models presents a challenge from a legal perspective, according to Verheeke. ‘In this matter, I also envisage a large degree of interaction with the Netherlands.’

Towards a Flemish PAS

In April 2014 the Flemish Government decided in favour of an Integrated Approach to Nitrogen (PAS). At the same time, it established the legal foundation for this PAS. After a preliminary PAS (VPAS) in mid 2015, the definite PAS (DPAS) should be completed in 2017 in order for it to be fully implemented in 2019. The calculation tool must also be ready for use in 2017.

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