In the framework of the “River Basin Management” program directed by the German Federal Ministry of Education and Research, the RWTH Aachen University and the Erftverband have developed an IT tool, called “DatenFluss”. This software-based load simulator was developed and validated in their joint project, “Material and data management in river basins, demonstrated for heavy metals in the Erft catchment (SAFE)”.

Figure 1 below illustrates the processes and pathways taken into account by DatenFluss for the calculation of nutrient and heavy-metal loads in watersheds from point and non-point sources. Figure 2 displays the corresponding decision tree for calculating loads. The objective is first to calculate loads as accurately as possible and second to use various approaches and combinations of approaches to determine how much results differ depending on the quality of the data set in terms of density and validity. Because of the underlying strategy of the model enabling its use in cases of poor data density or heterogeneous data sets, the model is also applicable in other watersheds. Therefore, it has been chosen as one of the emission load calculators to be used in the current project.


A new version of the DatenFluss program was implemented in the framework of uDig (User-friendly Desktop Internet GIS). The reason for the purpose of fulfilling was the need for data access facilities, export facilities and different river catchment structures. The advantage of such frameworks as uDig is that they provide access to most geo-data formats and an extensible graphical user interface. The reason for choosing uDig for implementing the new version of DatenFluss is that it aims especially for an extensible graphical user interface. DatenFluss itself consists of several modules:

• A network module provides a data structure for river catchment networks which consist of interconnected point sources, non-point sources and watercourse segments. Each source and segment contains a mass balance. Furthermore, the network module provides a traversing algorithm that produces an order of the sources and segments which respects the dependency of sources’ or segments’ input on output of other sources or segments.

• A mass balance module provides data structures for mass balance sheets that can be aggregated for river (sub-)catchments and exported.

• A load estimation module will provide the DatenFluss collection of load estimation methods and strategies to handle different data situations.

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