Reconstructing hydraulic conductivity field for hydrogeological modeling in an urban environment

• We develop an urban hydrogeological model (Pessac, France).
• We transform lithological unit descriptions to local hydraulic conductivity values.
• We model hydraulic conductivity fields using geostatistical methods.
• 2D and 3D modeling approaches are performed.
• The validation of the models is done through a case study.

Hydrogeological analysis of flow is largely based on the concept of hydraulic conductivity. In numerical hydrogeological modeling, a value of hydraulic conductivity must be assigned at each element of mesh. In heterogeneous geological formations, this value governs the average behavior of groundwater flow within an aquifer. The goals of this study are twofold: (1) development of a methodology to transform the description of lithological units into local hydraulic conductivity values and (2) development of a methodology for reconstruction of hydraulic conductivity fields on a 83 km2 of the Bordeaux urban area. Two approaches, a 2D approach and a 3D approach, based on geostatistical analysis are explained in details and compared. For both approaches, variographical analysis and ordinary kriging are carried out on the logarithmic of hydraulic conductivity and composite hydraulic conductivity is calculated using thickness-weighting to get horizontal and vertical hydraulic conductivities. The comparison of both approaches and the assessment of their potential and limitations suggest that the 2D approach is more appropriate than the 3D approach.