The basic physico-chemical properties of the karst spring Podstenjšek, depositing carbonates in the past shown by travertine blocks in its riverbed are given. Measurements and analyses of the spring and its water flow downwards at several sampling points showed that during the whole year the water precipitates calcium carbonate. The intensity of deposition depends on discharge and warming or cooling of water. From one litre of water at the distance of one kilometre from some to 36 mg CaCO3/l are deposited, the majority at the first 400 m.