Environmental tracers (18O, 3H, CFCs, SF6) exploitation for study of mean residence time and flow pattern of dripping water and karst springs (Moravian Karst)

Mean residence time and flow pattern was studied in unsaturated zone of Ochoz Cave in southern part of Moravian Karst by means of 18O in the years 2001 to 2003. The results of study showed relatively long residence time in the unsaturated zone (about 50% komponent with residence time exceeding one year). The proportion components coming from different reservoirs were computed from two components (soil/epikarst; meltwater). The results clearly indicate, that more than 50% of water (nearly 100% in 2003) in dripping waters was derived from soil/epikarst water, which originate from (late) summer precipitations (heavy 18O content)! It means that infiltrating snowmelt water was expelling (by piston flow effect) the summer water from soil and/or epikarst. Water from snowmelt was then lost by evapotranspiration in summer time. If this effect is common in Langer period, it can change composition of d18O in dripping waters and hence also in dripstones precipitating from these waters