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Vers une modélisation hydrologique adaptée à l'évaluation des pollutions diffuses : prise en compte du réseau anthropique. Adaptation au bassin versant de Naizin (Morbihan)

Abstract : As concentrations of pesticides in fresh waters sometimes exceed values imposed by the European Community, it would be useful if modelisation tools were available, which would allow for the assessment of contamination in a catchment area, and for the development of relevant solutions. Complex and highly non linear processes govern pesticidal behaviour in the environment. So we would rather study these processes and water movement separately, paying particular attention to the quick components of runoff. Since this work is based on a rural catchment area, with a bocage landscape, it has been necessary to look explicitly at the peculiarities of ploughed soils, as well as the anthropic network of hedges, ditches and roads which cut across the catchment area. The physically based distributed model Topog was adapted for this purpose. The mesh it uses to describe a catchment area's topography is based upon contour lines and their orthogonal lines, such that convergent and divergent areas are implicitly represented. Appropriate models led to theoretical estimations of the influence of ditches on a slope, and of the celerity of water transfer inside the anthropic network. Based upon these estimations, the role of the different kinds of elements of the anthropic network was then modelised. The modifications required by this chosen representation were then implemented in Topog. The resulting model was applied to the catchment area of Naizin (Morbihan). The terrain analysis made it possible to calculate topographical and topological (drained area) characteristics of the catchment area and the elements of its anthropic network. It was not possible, however, to establish a functional typology of the different kinds of elements based purely on these characteristics. The hydrological part of the model proved to be able to represent various processes. Calibration led to correctly simulated hydrographs, but didn't allow for identification of the prevailing processes. This arised partly because the data available, although numerous and varied, was not well adapted to this purpose. It seems essential to be able to characterise the behaviour of the different components of a catchment area, especially its soils, on a scale compatible with modelisation.
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Nadia Carluer. Vers une modélisation hydrologique adaptée à l'évaluation des pollutions diffuses : prise en compte du réseau anthropique. Adaptation au bassin versant de Naizin (Morbihan). Sciences de l'environnement. Doctorat Sciences de la terre, Université Pierre et Marie Curie Paris, 1998. Français. ⟨tel-02577946⟩

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