[en] Isotopic tracer method was used to determine flow paths, recharge and discharge areas for ground water in the karst of vicinity of Danube Delta Ecosystem. The spatial variation and the sets of isoconcentration lines for the deuterium average content correlated with the origin of the waters were the analytical tools for the analysis of the ground water flow paths, recharge and discharge areas in the karst. The study indicates that area is compartmentalized in four hydrological subareas: 1) the Northern part of the study area; 2) the second is part of Southwestern for which flow paths have a local character; 3) the third is the phreatic system that recharges from the Danube River. Flow paths are towards Southeastern and in Colina sink zone; 4) the last is mixing aquifer. The waters originated from mixing processes between the water with lower δD and the waters with high δD discharge in the Northern part of Razelm Lake, below the level of the lake's water. The deuterium content provides control and direct evidence of the high altitude water (above 1000 m) movement in limestone. In the substructures 1, 2 and 3 the intrusion of light isotopic water in the karst of study area occurs by conduit flow and the limestone drainage occurs by diffuse flow. The limestone drainage in mixing aquifer (substructures 4) is of conduit flow type. The hydrostatic pressure and the geometry of conduits control the movement of the light isotopic water. The isoline maps for deuterium content point out both flow path of ground water and heterogeneity of geological structure. (authors)