Modelling the mobilisation of contaminants from catchment soils to surface water

The aim of this project will be to seek minimum model complexity to run process oriented models on a landscape scale. For this purpose we will identify a) critical meteorological driving parameters, b) key variables such as DOC, pH and capacity terms such as ion-exchange and c) important thermodynamic or kinetic reactions. For the former, we will make use of the large meteorological data set available at the Krycklan site. For the latter, metal speciation in presence of dissolved organic matter can be studied in detail using the WHAM VI program code. This widely applied model has recently been calibrated to the Krycklan catchment [Cory et al. 2007, Köhler at al. submitted]. After a sensitivity analysis of controlling factors, selected features of WHAM and relevant solid-liquid exchange reactions will then be incorporated into the PHAST code. In some of the Krycklan catchments, the hydrological control of water levels are already well studied and catchment characteristic response functions of DOC and metal release as a result of rainfall pattern and discharge of at least two catchments will be implemented into PHAST. The long time series of chemical measurements in two catchments will then be used to fit the model and identify weaknesses in the above described approach. In addition to this, it is planned to calibrate the earlier mentioned WITCH model to compare the different approaches