Apport du traçage physico-chimique naturel à la connaissance hydrocinématique des aquifères carbonatés


Jacques Mudry


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Publication Date

January 1987


Carbonate aquifers bear a memory of the recharge episodes. The environmental, physical and chemical tracing allows to specify the origin of the discharge water passing through the spring, hence it is an essential complement to the hydrodynamical studies. The first part of this thesis deals with the study of the time-variations of the physical and chemical content of the karst springs, on weekly and daily bases. The second part tries, from the chronological studies, to compute the amount of the reserves and of the underground flow in the total discharge of the spring, during flood and hydrological cycles. The third part purposes to prospect the hydrogeological regions (Jura Mountains and Southeastern France) with synchronous snapshots. This work allows a schematization of the behavior of the system. At the end of a depletion period, the precipitations percolate, accumulate and replace the stored water and solutes in the various "unsaturated" reservoirs -soil and epikarst- and saturated reservoirs -flow axes and capacitive zones-. The outlet records the chemical character of both media: surface (=immediate infiltration) and saturated (=piston effect) zones. The effective and massive contribution of the underground flow to the total discharge occurs in a mixture with the reserve water, often after the hydrograph peak, at the beginning of the recession. The depletation of the reserve begins when the contribution of the underground flow stops in the mixture. Hence the physical and chemical investigation allows weIl to discriminate between hydrokinematics and hydrodynamics, that is transit and transfer, respectively. The identification of the uninfluenced period, with help of snapshots, allows getting much information about the geochemical environment of the karst, its hydrocinematical behavior at a regional scale in a mountain zone, the location of recharge area and reserves, the mean age of permanent reserves and human influence on their quality. The representativeness of methods and study periods has been proved.


Unsaturated Zone, Spring, Hydrochemistry, Hydrodynamics, Hydrological Methods, Environmental Isotopes, Water Depletion, Floods, Water Recession, Jura Mountains

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