Interpretation of pumping tests in a mixed flow karst system

Jean-Christophe Maréchal (1) , Bernard Ladouche (1) , Nathalie Dörfliger (1) , Patrick Lachassagne (1)

1 BRGM - Bureau de Recherches Géologiques et Minières

A long-duration pumping test performed in the conduit of a mixed flow karst system (MFKS) is analyzed and interpreted. It constitutes a unique experiment of catchment wide response of a karst system, with drawdowns measured both in the pumped conduit and in the matrix. A modeling approach is proposed for this interpretation. The developed double continuum model consists of two reservoirs - karst conduits and the surrounding carbonate rocks - between which flow exchange is modeled using the superposition principle and the hypothesis of Darcian flow in the matrix, considered as an equivalent porous media. The karst conduits are assumed to have an infinite hydraulic conductivity. Model calibration results in a very good match (relative root mean square - rRMS = 2.3 %) with drawdown measured at the pumping well (karst conduit). It shows that the matrix hydrodynamic parameters (hydraulic conductivity and storativity) have a greater influence on the drawdown than the storage capacity of the conduit. The accuracy of the model relies mostly on a very good knowledge of both pumping rate and natural discharge at the spring (with and without pumping). This type of approach represents an advance in double continuum modeling of karst systems. It also provides a methodology for the management of water resources from karst aquifers.

Mots clés: Karst system; pumping test; conduit network; karst modeling; spring; groundwater; permeability; porosity; hydraulic conductivity; simulation; mediterranean

Domaines: Hydrologie; Milieux et Changements globaux

Jean-Christophe Maréchal, Bernard Ladouche, Nathalie Dörfliger, Patrick Lachassagne. Interpretation of pumping tests in a mixed flow karst system. Water Resources Research, 2008, 44, pp.W05401. ⟨10.1029/2007WR006288⟩. ⟨hal-00458978⟩