Présentations Colloques

The discrepancy between the complexity of real flow behavior and the simplicity of analytical flow models makes the interpretation of transient well tests an ambiguous and imprecise task. Hydrogeology practitioners commonly use conventional Theis-like models for aquifer diagnostics, making the implicit postulate of a radial flow regime, leading to a significant degree of error when the real flow behavior is in fact non-radial. **Derivative analysis combined with a flow dimension interpretation provides detailed knowledge of real flow behavior. A bilog plot of ds dlog(t) time series emphasizes typical stable slopes that are interpreted as successive flow regimes with specific flow dimension values. This parameter reflects the transient shape of the cross-flow area as the pressure front-pulse is diffused through the aquifer. The hydrodynamic understanding of flow regimes successively occurring during a pumping test is thus a very promising avenue for the analysis of complex aquifer behavior.**The statistical significance of the non-radial flow regime (n ≠+ 2) in nature is emphasized by the analysis of n occurrences from numerous pumping tests in various geological settings. Specifically, it is shown that spherical or pseudo-spherical regimes (n = 3 or 2 < n < 3) are frequently produced by weathered crystalline aquifers, thick alluvial deposits and leaky aquifers.**Based on a numerical approach, the aquifer features that induce such 2