Improving hydrogeological understanding through well-test interpretation by diagnostic plot and modelling: a case study in an alluvial aquifer in France

The study of groundwater resources using pumping test data is usually carried out with the Theis solution, which enables hydraulic parameters porous aquifers such as transmissivity and storage coefficient, to be estimated from water-level drawdown. However, fitting can fail provide only an indication that pumped aquifer has a complex structure. Here, diagnostic plot on log-derivative drawdown used identify flow regimes thus heterogeneities, leading plausible conceptual models. Nevertheless, insufficient must accompanied by further modelling because nonuniqueness signal. proposed approach applied alluvial plain in France, known deposition processes change over time, resulting channel belts limited low-permeability deposits floodplain or three-dimensional (3D) interconnected structures. Six analytical models were simulate its derivatives during three-day transient test. performed well showed four models, highly contrasted hydrodynamic behaviours, may correspond diagnostic. joint use pumping-well observation-well allowed appropriate model identified—a dual-permeability characterizing multilayer aquifer. matched geological observations boreholes corroborates fluvial sequence stratigraphy plain. here tool explore 3D architecture reservoir at scale depositional floodplain.