Mapping oxygen stable isotopes of precipitation in Italy

•Isotope data in precipitation in Italy.•New meteoric water lines and new map for δ18O distribution in Italy are provided.•Local effects on isotope distribution in precipitation in Italy.

Study regionItaly.Study focusThe oxygen isotope composition from 266 pluviometers was used to study the spatial variability of δ18O and its relationship with Italian orography. The local meteoric water lines (LMWLs) of northern, southern and central Italy and Sicily are reformulated and a new definition of isotopic variations with elevation is provided.New hydrological insights for the regionAltitude and, to a lesser extent, latitude are the main geographical factors affecting the isotopic signature of precipitation in Italy. A high-resolution map of the spatial distribution of 18O content in precipitation was created using the identified relationship between δ18O/Latitude-Altitude and the spatial distribution of the residuals. The general features of the δ18O distribution map may be summarised as follows: δ18O distribution over the Alps clearly depends on latitude and altitude, whereas over the Apennines, which run down the whole peninsula from north-west to south-east, it is more affected by altitude, the contour lines roughly following the axis of the chain. The isotope compositions on the western side of the peninsula are generally higher than those of the east at the same elevation and latitude; they are more or less uniform in the northern plain of Italy.