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The water management in Croatia is a national priority since about 50% of the country consists of karst. It is thus of vital interest to have a complete as possible knowledge of all related factors, including the precipitation as the input into the water system. Besides meteorological data, isotopic tracers are important tools to understand and quantify this complex problem. Very little information exists, however, about the isotopic composition of precipitation in Croatia. Therefore, we propose to collect precipitation through the GLOBE program in order to establish an atlas of the isotopic composition of precipitation for as wide an area of Croatia as possible. GLOBE (Global Learning and Observations to Benefit the Environment) is a worldwide primary and secondary school-based science and education program. In Croatia, about 100 schools are involved in GLOBE, and about 25 contribute in this nationwide collection of precipitation. These samples are then sent to and analysed in the Stable Isotope Laboratory at Rijeka University (SILab Rijeka). First results will be shown at the Conference.

Na Sveučilištu u Rijeci osnovan je prvi hrvatski laboratorij za masenu spektroskopiju stabilnih izotopa s ciljem istraživanja krškog područja te proučavanja procesa u hidrološkim, hidrogeološkim i meteorološkim ciklusima. U radu su izneseni preliminarni rezultati mjerenja δ 18O u vodi za tri izvora rijeke Gacke. Interpretaciju rezultata mjerenja upotpunjuju podaci iz Državnog hidrometeorološkog zavoda.

A large fraction of Croatia (nearly 50%) consists of Karst, and the study of related hydrogeological problems are high on the country’ s priority list. Therefore, Croatia’ s first laboratory for stable isotope mass spectrometry has been set up at Rijeka University. It features a Delta+XP , fitted with a Gas Bench (incl. a 96-position autosampler, generally used for δ 18O analysis in water and carbonates) and a Dual Inlet. Addition of an Equilibration Unit is planned for high-precision δ D measurement. Several home standards (ca. 40 l each) covering a δ 18O range between – 1.6 and -26, 4 have been calibrated against standardized samples. First δ 18O measurements serve as examples for the application of IRMS data to determine the dominant recharge areas of Gacka river and Vrana lake. We gratefully acknowledge supported by the MZOS in project 0062011 and by the IAEA in project CRO/8/006.