Stable isotope composition of the meteoric precipitation in Croatia

Abstract

The precipitation is the input into the water system. Its stable isotope composition has to be known for the proper use and management of water resources. Croatia is not well represented in the Global Network of Isotopes in Precipitation (GNIP) database, and the geomorphology of the country causes specific local conditions. Therefore, at the Stable Isotope Laboratory (SILab), Rijeka, we monitor the stable isotope composition (δ18O, δ2H) of precipitation. Since δ18O and δ2H are well correlated, we concentrate the discussion on the δ18O distribution. Together with GNIP, our database contains 40 stations in Croatia and in the neighbouring countries. Their different latitudes, longitudes and altitudes give information of great detail, including the influence of the topographic structure on the precipitation in the south-eastern part of Europe, as well as the complex interplay of the different climate conditions in the area. Within a few hundred kilometres, the stable isotope values display a significant change from the maritime character in the south (mean δ18O around−6 to−8%‰) to the continental behaviour in the north (mean δ18O around−8 to−11%‰). Depending on the location, the mean δ18O values vary with altitude at a rate of approximately−0.2%‰/100 m and−0.4%‰/100 m, respectively. Also the deuterium excess has been found to depend on location and altitude. The data are being used to construct a δ18O map for the entire area.