Within the subsurface convective system which constitutes the thermomineral waters of which the meteoric origin is proved by the oxygen—deuterium couple, the associated gases, free or dissolved, may represent the only “juvenile” component in this cycle. The “juvenile” origin of the gases can be clearly established through ascertaining the isotopic composition of certain elements: argon, nitrogen, carbon and helium. The study of these gases associated with thermomineral waters has been undertaken systematically since 1976. One of the first objectives of these investigations has been the determination of the carbon isotopic compositions of the carbon dioxide—bicarbonate system for ∼50 thermomineral springs in various geological settings: the Massif Central, Pyrénées, and Vosges mountainous regions, France.
A geothermal model of Lake Assal region (F.T.A.I.) was derived from in situ observations and chemical and isotopic studies of hot and cold springs.
Les ressources exploitables effectives sont tres generalement inferieures aux ressources naturelles, par l'effet de diverses contraintes physiques ou economiques qui limitent les possibilites d'exploitation. Mais, dans certains cas, au contraire, ces ressources peuvent depasser largement les ressources naturelles (beaucoup d'aquiferes alluviaux tres lies aux rivieres). De meme, les quantites d'eau prelevables pendant une longue
A general review of the variations in tritium content in the present-day northwest Saharan waters is given, using data concerning several years of rain at the Beni-Abbès station, by the fresh surface waters and those of an evaporite basin, resulting from internal drainage of Wadi-Saoura, where the concentration by evaporation reaches the point where the salts precipitate (halite and gypsum). In addition to providing useful data for the interpretation of weather and present-day hydrological phenomena, it informs us about the maximum tritium contents of the waters liable to recharge the groundwaters.
