Spatial and temporal variations of δD and δ18O in mean monthly precipitation and groundwater are described by means of a simple water vapour advection model, which links the isotope data to the vertically integrated horizontal flow of vapour. This model yields a temperature dependence of the isotope precipitation data, which is compared with the experimental temperature effect. Short-term variations of δD and δ18O in mean daily water vapour reflect the varying influence of different air masses on the local weather. A spectral analysis of these short-term variations yields predominant periodicities of about 10, 20 and 30 days, which are related to the long-wave pattern of the zonal drift in the upper troposphere. δD and δ18O in plant material (tree rings, peat), solids, lake sediments, speleothems and in other carbonates of paleoclimatic interest is primarily influenced by the isotopic composition of local precipitation, atmospheric moisture and by temperature dependent isotope fractionation. The relevance of such fossil material (peleowaters included) fo paleoclimate and in particular for the reconstruction of the water vapour circulation pattern in the past is discussed.