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Delta 18O Spatial Distribution of Precipitation in Croatia

The precipitation as the input into the water system and its stable isotope composition is a basic part of the knowledge that is required for proper use and management of water resources. Thus there is an increasing need for research programs that use spatial precipitation data to identify and characterize regional water resource issues that have the potential to severely impact large sectors of society in the coming decades. The light stable isotope ratios of water (δ2H, δ18O) are parameters that can be easily and routinely measured for almost any water sample and which can preserve information on the climatological source (i.e., the location, time, and phase of precipitation) and the history of water after precipitation. Environmental water resources, including ground and surface water, derive their H and O isotopic composition primarily from the meteoric precipitation [Gat, 1981 ; Kendall and Coplen, 2001 ; Smith et al., 2002 ; Dutton et al., 2005]. Croatia is not well represented in the GNIP data set, and the geomorphology of the country can cause specific local conditions. Therefore, at the Stable Isotope Laboratory (SILab Rijeka) we monitor the stable isotopic composition (δ18O and δ2H) of precipitation in a large number of stations in various locations all over Croatia at different altitudes and latitudes. The δ18O, δ2H and d-excess altitude effects have been extracted from the measured data and provide a data base of precipitation isotope ratios.The diverse climate conditions in Croatia are seen e.g. in the altitude- δ 18O relationship. Spatial analysis of δ18O data in a GIS environment is a new endeavor, and developments in this area are well-timed to take advantage of the recent emphasis on catchment to basin-scale hydrology.

spatial distribution; stable isotopes; precipitation; empirical model

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