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Modélisation orientée décision des processus de transfert par ruissellement et subsurface des herbicides dans les bassins versants agricoles.

Abstract : The use of pesticides in modern agriculture is a major problem for ecosystems and human health. One of consequences is major problems is the degradation of the surface and subsurface water quality for consumption and water quality of ecosystems.

There is a real need for operational tools to aggregate of the processes of transfers at the level of the catchments in order to predict the pesticides contaminations of water. The main operational tools are environmental indicators which use is fast and simple. They assess only a level of risk, but do not discretize it in space and time.

An oriented decision model of herbicide transfer by surface runoff and subsurface flow is proposed here. It produces a semi-quantitative valuation of the herbicides river contamination on small cultivated catchments (a few tens km²) during a few months following the treatments. An original spatial representation is established. It is based on agricultural practices and flow path ways in catchment area by using tree structure linking field outlet and their contributory areas. This spatial representation allows a realistic and operational modelling for the end users.

This model is based on a spatial structure that integrates hydrographic, ditches and hedges networks of the catchment. The major processes of herbicides transfers in catchment on low permeable bedrock are the surface runoff and subsurface flow. The surface runoff is calculated according to the surface conditions and the contamination level of subsurface flow is calculated according to the depth of shallow groundwater from the soil surface.

To generate realistic scenarios of weeding technical routes on catchments including a significant number of fields, a decisional model was developed and coupled with the transfer model. This decisional model simulate the farmer decisions in various organization levels (fields, farms).

This model was applied to the catchment of Frémeur, catchment of the network Bretagne Eau Pure.
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Submitted on : Tuesday, March 28, 2006 - 11:47:50 AM
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Florent Tortrat. Modélisation orientée décision des processus de transfert par ruissellement et subsurface des herbicides dans les bassins versants agricoles.. Sciences de la Terre. Agrocampus - Ecole nationale supérieure d'agronomie de rennes, 2005. Français. ⟨tel-00012049⟩

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