Plitvice Lakes are a karst phenomenon best known in the world for tufa barriers that have over time cascaded the canyon of the river Korana into a series of 16 beautiful lakes. Tufa barriers are formed only in certain geological, hydrological, geochemical and biological conditions that favour the deposition of calcite minerals from aqueous solution and their accumulation in the form of barriers/barriers along the flow. Any small violation of the mentioned conditions can endanger the survival of the barriers as well as their further growth. This work presents the application of a geochemical mass balance model NETPATH-WIN by which we calculated the partial pressure of carbon dioxide, saturation of calcite and dolomite mineral phase as well as the transport of calcite, dolomite and carbon dioxide along the lake. In two research periods it was found out that the most calcite can be deposited on the sections of the flow between Matica and Prošćansko Lake and Kozjak and the Korana River in the village of Korana. Also, the verification of the model by comparing the saturation index and the sign of transport (precipitation/dissolution) was not successful in any case, which imposes the need to verify the model using geochemical reaction-path models and to use a stable carbon isotope content during modelling.