Jeannin, Pierre-Yves

2003, Kovács, Attila, Perrochet, Pierre, Jeannin, Pierre-Yves

This thesis presents a method for characterizing flow systems in karst aquifers by acquiring quantitative information about the geometric and hydraulic parameters of a karst conduit network from spring hydrograph analysis. The investigation method applied consisted of constructing simple conceptual models of karst systems, and deducing analytical formulae describing the connection between aquifer parameters and hydrograph recession coefficient. The resulting formulae were then applied for evaluating input parameters for numerical models of the Bure aquifer (Jura, Switzerland). The comparison between model simulation results and real-world data permitted to test the applicability of the analytical formulae. The Bure test site also provided as a basis for evaluating some general characteristics of conduit networks by steady-state numerical models. Analytical formulae identified two, significantly different flow domains, depending on the overall configuration of aquifer parameters. During the baseflow recession of mature karst systems, the conductivity of karst conduits does not influence the drainage of the low-permeability matrix. In this case the drainage process is influenced by the size and hydraulic parameters of the low-permeability blocks alone. This flow condition has been defined as matrix-restrained flow regime (MRFR). During the baseflow recession of premature karst systems and the flood recession of mature systems, the recession process is dependent not only on the hydraulic parameters and the size of the low-permeability blocks, but also on conduit conduc