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Abstract:
The karst of the Eastern compartment of the carbonated Lower Cévenne (Gard) - This text summarises 10 years of exploration and study of the eastern karst of the Gardon river basin above Alès. Karst concerns 5 facies: Trias, Hettangian-Sinemurian (rich in limonite and pyrites), Upper Bajocian - Lower Bathonian (rich in pyrites), Upper Jurassic and Barremian. This lager is broken into more or less rolling panels, which have collapsed towards the Alès rift. Tridimensional systems draining this karst are considered to be evolving toward better performance. It is a remarkable case of natural organisation. Structure is deduced from function. A morphologic approach explains the systems history. Three of the four identified karstic systems are simple. They are partial a natural models of the fourth: the Fonts karstic system. We describe on detail some elements of its structure (caves for ex.) and of its functio-ning (hydrodynamic, hydrochemistry). We show through pumping that the Cauvel river feeds the Fonts spring and the Carabiole spring. The effect of geological and geomorphologic characteristics of the spring site on water output is mentioned. We describe the realisation of a pumping station driving subterranean Cauvel river water a 100m back and point out the usefulness of speleological information.