AGE AND RECHARGE AREA OF THERMAL WATERS IN LADEK SPA (SUDETEN, POLAND) DEDUCED FROM ENVIRONMENTAL ISOTOPE AND NOBLE-GAS DATA

Environmental isotope and noble gas data are shown to identify the glo bal parameters of the thermal water system in Ladek Zdroj (Spa), Sudet en, Poland. The mean C-14 age is about 5 ka, and the delta(18)O and SD data are assumed to yield the mean altitude of recharge by making use of the altitude effect known for the Sudeten area. The natural discha rge rate multiplied by the C-14 age gives the total volume of water, w hereas the volume of the host rock is roughly estimated for three scen arios of system dimensions. For these scenarios, the ratio of these tw o volumes yield a total porosity in the range of about 0.005-0.014, wh ich, in a good approximation, should be equal to the matrix porosity. Laboratory determinations of unaltered rock samples yield a matrix por osity of 0.008 +/- 0.001. For the three scenarios, the tracer age and matrix porosity are shown to yield a hydraulic conductivity for the wh ole system in the range 0.8-1.6 x 10(-8) ms(-1), without any knowledge of the fissure network parameters. Noble gas temperature compared wit h known temperature dependence yields the mean altitude of the recharg e area equal to that found from the delta(18)O and SD data. The radiog enic He-4 excess and Ar-40/Ar-36 ratios are consistent with the mid-Ho locene age determined from the C-14 data.