Modelling scenarios in ArcNEMO in preparation for European legislation: A policy perspective

In order to substantiate the agricultural measures for the Nitrate Directive action programmes and WFD river basin management plans on a regional scale, the Flemish Environment Agency initiated a project at the end of 2011 to develop a new spatially distributed mechanistic nutrient emission model for the Flemish region in Belgium. The requirements for the model were that the model needed to be able to calculate the water, N- and P-balance of the soil for the agricultural, as well as the water flow and transport of N and P to the surface water land in Flanders. The model had to be based on the available data in Flanders about the parcels, farms, soils, climate, … for the whole region. The model had to be designed in a way that it allowed the government to calculate a broad range of measures and scenario’s , including long term effects on surface water inputs. In 2014, a first release of the model named ArcNEMO was available. In preparation of river basin management plans 2016 to 2021 and the actualization of the Nitrate Directive action programme for Flanders, different scenarios were set up to be run with ArcNemo for the period 2010 to 2031. The different scenarios are classified in 3 types: - Variation in the quantity of applied fertilization (fertilization standards) - Variation in fertilization types and practices (animal manure vs chemical fertilizer, time of fertilization, …) - Variation in agriculture practices (eg. buffer strips, catch crops, …) The project will be finalized in the first semester of 2015. An overview of scenarios will be given and insight about how scientists, model developers and policy makers have come to a final set of scenarios. The ArcNemo results for the relevant scenarios will be presented and explanation will be given about how the results were accepted and interpreted by the involved scientists and policy makers. Considerations will be made about future improvements to the whole process of using modelling for future policy development.