Alain Devos

Structural control on surface flow in karstic environment

Aquifer hydrodynamical properties, hydrogeological tracing, mapping and piezometric monitoring characterised underground flow in calcareous environments. Surface flow study during low-water season showed water supply spatial heterogeneity due to calcareous aquifer anisotropy. It also underlined the role of structure on water transfer and exchanges between aquifers and rivers. By controlling the hydraulic gradient between the streams network and the saturated zone, structure compartmentalisation moderated considerably the role of fracture on underground flow. Several examples of calcareous basins from eastern France were studied.

Les plans directeurs de la Grande Guerre - Une nécessaire innovation cartographique

Le theme de la Grande Guerre a fait l’objet de nombreuses publications dans le cadre du centenaire dans lesquelles l’approche est generalement historique ou sociale mais pas spatiale. Pourtant, l’archeologie de la Grande Guerre, les recherches genealogiques, les travaux des associations et le devoir de memoire utilisent de nombreux extraits de cartes militaires de la zone de front ou de plans directeurs. L’objectif de cette contribution est double. D’une part, elle replace les plans directeurs dans le contexte des cartes francaises existantes avant la Grande Guerre, demontrant ainsi la necessite d’innover du fait de l’adoption de la guerre de position par les differents belligerants, marquee par plusieurs rideaux defensifs de tranchees. Et d’autre part, elle propose de presenter les clefs de lecture des plans directeurs (systeme de coordonnees, construction, echelles, projection, legende).

Impact of lateral variations of geologic facies on water resources in homogeneous basins: example of tertiary plateaus in the Paris Basin

Spatial disparity of run-off conditions during low-water period in homogeneous watersheds depends on the degree of incision of valleys, but may also be influenced by a structural partitioning or some lateral variations in the aquifer lithology. For small basins (area <300 km2), often hydrometrically unsupervised, campaigns of serial flow measurements, gauging, conductivity and temperature are achieved. The Ardre basin, localised in the Tertiary formations of the Paris Basin is used as a workshop basin. Results validated by hydrological and physico-chemical profiles show increased hydrological yields in the basin which correspond to the increase in the thickness of aquifers and their porosity. These lateral variations of facies and of aquifer thicknesses are related to Eocene sedimentary conditions (Lutetian) for homogeneous basins, which explain the spatial disparity of water resources.