Using flow dimension sequences to interpret non-uniform aquifers with constant-rate pumping-tests: A review

Today it is still common practice to analyse pumping tests assuming Theissian conditions, resulting in interpretations that are at best grossly approximated, if not erroneous, with potentially negative impacts on the quality of water resource management. Over the last several decades, numerous technological advances in hydrogeology have been developed that make it possible to perform more realistic analyses of heterogeneous, non-purely Theissian flow systems (e.g. aquifers with non-uniform geometry and/or hydraulic properties). For this study a catalog of available behavioral flow models was compiled from the literature and consolidated into a unique interpretative scheme. This is based on two first-order flow modelling breakthrough developments derived from research works: the derivative analysis (Bourdet et al., 1983) and the flow dimension theory (Barker, 1988). Each derivative type-curve is segmented and converted into a sequence of stable flow dimensions, in order to integrate a large panel of models into a comprehensive conceptual hydrodynamic and interpretative framework. This allowed us to conduct a thorough discussion on a range of different hydraulic conditions and their associated most common responses to constant-rate pump tests, namely, the linear, bilinear, radial, and spherical flow regimes and various sequential combinations of these elementary flow regimes. The relevance of the catalogued behavioral flow models is examined based on the realism of their postulates and on their frequency of occurrence in the field. The proposed diagnostic methodology makes it possible to further refine the interpretation of pumping tests and to routinely detect complex aquifer conditions. Keywords: Transient tests, Flow dimension, Diagnostic plots, Numerical modeling, Non-Theis aquifer