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Titre : | Optimizing the size of grassed buffer strips to limit pesticides transfer from land to surface water in overland flow. |
Auteurs : | ALEXANDRA FONTAINE |
Type de document : | Mémoire de fin d'études |
Année de publication : | 2009 |
Résumé : | Grassed buffer strips are seen as an effective way to limit pesticides transfer from land to surface water in overland flow. Recommendations are currently provided to determine the size of grassed buffer strips according to the hillslope's length, but it is not always adapted. The optimal size of a grassed buffer strip actually depends on the site-specific conditions, including the soil type, the local climate, the vegetation cover and the hydrological regime. This study is part of the process for designing a practical tool to easily determine the optimal size of a grassed buffer strip according to its location. The tool will rely on the use of the Vegetative Filter Strip Modeling System, and the objective was to assess the role of the factors influencing the performance of grassed buffer strips. Qualitative and quantitative sensitivity analyses were performed on a new version of the model which includes a subroutine developed for internal use to take account of the presence of shallow water tables. The results highlighted that in all the cases, the vertical saturated hydraulic conductivity of the strip's soil is one of the most sensitive parameters which should be carefully estimated by the user. When there is a shallow water table, the strip's saturated soil water content and the water table depth alsoappear to be sensitive. On the contrary, parameters related to the capacity of the agricultural field for generating runoff, such as the curve number and the antecedent soil moisture condition of the field, do not seem to the efficiency of the grassed buffer strip. Still, the results obtained remain dependant on the statistic distributions which were assumed and are related to particular sites. The results also showed that the subroutine is not finalized for the moment and will be improved to accurately represent the different types of surface runoff. |
Spécialité : | Géologie |
Numéro de promo : | 69 |