Development and application of the modelling system J2000-S for the EU-water framework directive

The scientific sound definition of measures to achieve the goals of the EU water framework directive (WFD) acquires spatially distributed analyses of the water and substance dynamics in meso- to macro-scale catchments. For this purpose, modelling tools or systems are needed which are robust and fast enough to be applied on such scales, but which are also able to simulate the impact of changes on single fields or small areas of a specific land use in the catchment.

To face these challenges, we combined the fully-distributed hydrological model J2000 with the nitrogen transport routines of the Soil Water Assessment Tool SWAT model, which are normally applied in a semi-distributive approach. With this combination, we could extend the quantitative focus of J2000 with qualitative processes and could overcome the semi-distributed limitation of SWAT. For the implementation and combination of the components, we used the Jena Adaptable Modelling System JAMS (Kralisch and Krause, 2006) which helped tremendously in the relatively rapid and easy development of the new resultant model J2000-S (J2000-Substance).

The modelling system was applied in the upper Gera watershed, located in Thuringia, Germany. The catchment has an area of 844 km2 and includes three of the typical landscape forms of Thuringia. The application showed, that the new modelling system was able to reproduce the daily hydrological as well as the nitrogen dynamics with a sufficient quality. The paper will describe the results of the new model and compare them with the results obtained with the original semi-distributed application of SWAT.