Test and application of the surface-subsurface physically based reactive transport model CATHY on a vineyard hillslope
Test et application du modèle à base physique de transport réactif de contaminant en subsurface CATHY sur un versant viticole
Résumé
In the context of the European Water Framework Directive (WFD, 2000/60/EC), which aims to achieve a good ecological and chemical status for all natural aquatic environments, tools to help understand and quantify pesticide transfers in agricultural watersheds are necessary. Models which are physically based and spatially distributed can be particularly useful for representing in detail processes and interactions between the soil surface and subsurface and thus to evaluate the management of landscape elements remediation. The present study aims to test and validate a recently added reactive transport to the coupled surface water/groundwater model CATHY, in order to represent pesticide transfers. Contaminant reactions implemented in CATHY for this study are linear adsorption and degradation (first order kinetics). The advection part of the model is solved according to the finite volume method and reactions are computed on volumes using a sequential non-iterative approach. The CATHY model has been tested on laboratory data and with a Morris sensitivity analysis and is applied now in real field conditions, on a vegetative buffer strip monitored by Irstea in a vineyard catchment (Beaujolais, France). The site is instrumented with lysimeters, flow and solute concentration measurement devices. This test represents a complex step into the model validation, initial and boundary conditions are not fully controlled, and field parameters measurement are not fully known.
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