Isotope Investigation of Lake Vrana and Springs in the Kvarner Area

Abstract

From the strong enrichment of 2H and 18O in the water of Lake Vrana (Cres Island, Croatia) we concluded that there is negligible outflow from the lake. Regional recharge could be of minor importance since the amount of local precipitation is about the same as that of evaporation from the surface and there is no major outflow. From the existing isotope data no evidence was found of an inflow of fresh karstic water in the deepest part of the lake. Mean residence times of 30–40 years were obtained for water in the lake if the enrichment of tritium due to evaporation is taken into consideration. At the same time, the homogeneity of the isotope results indicates good mixing of this deep karstic reservoir. Seven springs were sampled in the Rijeka region and residence times between 5 and 10 years were calculated for the water contained in them. © 1997 John Wiley & Sons, Ltd.