Présentations Colloques

Oral Presentation
8.10
Session 8.10: Recent developments in groundwater modeling and mathematical tools in Hydrogeology
Seraphin Pierre
A multi-layer transient groundwater flow and transport model of the Crau aquifer using stable isotope tracers
In the last decades, the Crau aquifer (Southern France) became an example of the complexity of anthropogenic aquifer management. To supply a high consuming irrigation practice, water is diverted from the Durance River, and the large amount of irrigation return flows constitutes the main recharge of the Crau aquifer (70%), which is in turn largely exploited for domestic, industrial and agricultural water use. A possible reduction of irrigation fluxes due to a need of water saving or to a future land-use change could endanger the groundwater resource. Available hydrogeological models of the Crau aquifer only consider the well-known superficial reservoir made of puddingstone. However, the underlying heterogeneous layer considered the basement shows groundwater flows evidences (springs and water table levels within this layer). An updated transient groundwater flow and transport model considering this new multi-layer geometry is built, integrating the simulation of conservative tracers. The database used to validate the simulation is based on an extensive groundwater sampling covering time variations and spatial distribution of delta18O and delta2H signals over the whole aquifer. Essential to model groundwater flows, some aquifer properties are estimated by independent methods. The permeability fields of the two reservoirs are stochastically calibrated by looping steady-state simulations. The poorly known specific yield distribution is estimated using the water table fluctuation method on extreme rainfall events. These properties implemented in a transient hydrogeological model allow simulating the seasonal behavior of this aquifer, and thus, establishing a sustainable management of this resource.
France