An integrated modelling framework to estimate the fate of nutrients: Application to the Loire (France)

Many European countries face high nutrient loadings and the scientific community is asked to provide tools and methodologies to quantify the pressure on the environment originating from agriculture. This paper presents a tiered approach for addressing nutrient fate at various scales that makes best use of readily available data at EU level. A statistical nitrogen source apportionment model is applied in the Loire and Vilaine river basins to identify areas with highest losses. The physically based model SWAT is then used to identify within those areas, the major processes and pathways controlling nutrient losses. It is shown that groundwater is the major contributor to total nitrate load in the streams. Finally, the farm-scale model EPIC is used to elaborate appropriate farming practices. It is predicted that using a winter catch crop will reduce significantly nitrate leaching without endangering the farm economic sustainability.