Pesticides Research, 64 – Technical Documentation of PestSurf, a Model describing Fate and Transport of Pesticides in Surface Water for Danish Conditions

Technical Documentation of PestSurf, a Model describing Fate and Transport of Pesticides in Surface Water for Danish Conditions

Summary and conclusions

PestSurf is a tool developed with the purpose of carrying out simulations to assess the expected effects of an active substance on adjacent surface water bodies. The tool consists of a number of programme modules, which together carries out the necessary calculations.

The kernel of the tool is four model setups of MIKE SHE (hydrological catchment model) and MIKE 11 (model for streams and ponds). Originally, these models were made for a moraine clay area (Lillebæk) and a more sandy area (Odder Bæk). These two original models in a slightly modified form are contained as the basic scenarios. In each of the two areas, a pond is created to make it possible to simulate either a stream or a pond for each type of area.

All parameters, which are not of relevance for active substance simulations, are l°Cked in the model. However, the user can, through the user interface of the tool, choose which model setup the calculations must be based on, enter the properties of the active substance, choose a buffer zone and run the model.

When PestSurf is started, the input values entered are recalculated to model parameters, and wind drift and dry deposition is calculated and written to time series files, specifying the actual input to the stream model. Depending on which crop the calculations are carried out on, a pre-calculated file with the required water fluxes is selected. PestSurf only governs the calculation of solute transport and transformation.

The report contains the technical Documentation for the processes not described in the existing MIKE SHE and MIKE 11-manuals, that is wind drift, dry deposition, calculation of the dosage hitting the soil surface, colloid transport and processes of relevance for transport and transformation of the active substance in streams and ponds. Furthermore, the user interface is described.

The calibration of the models and the selected scenarios are described elsewhere.