Integrated catchment modelling: an application to Molenbeek catchment, Belgium

Hydrological, hydrodynamic and water quality models are often used to simulate surface water in a correct way to be a good basis for decisions regarding the development and management of water resources. Molenbeek is one of the main tributaries of the River Dender basin (Belgium). The hydraulic model is implemented by using the MIKE 11 software of the Danish Hydraulic Institute (DHI). It is a very detailed physically-based model: measured cross-sections are inserted at least every 40m and all significant structures (bridges, weirs, culverts and control structures) are considered. A simplification to the detailed model is performed to overcome the difficulties of running the model with higher time step (because of numerical instability problems). The simplified model is calibrated to the detailed one to make sure that it has a comparable performance accuracy. In this way, also an accurate and fast model for Molenbeek brook is implemented. The hydrodynamic model is linked with a hydrological model, which was calibrated and validated on the basis of new concepts. In addition, water quality modules (advection-dispersion and water quality) are applied to the river. Therefore, it was important to study the activities (agricultural, domestic, and industrial) that influence the river water and their quality. Model calibration was performed on the basis of available measured flow and water quality data.