Springs represent an important point or area on the surface, where groundwater flows from the aquifer and creates a visible surface flow. The dynamics of the spring gives us a lot of information about the aquifer and its recharge area, therefore the knowledge and understanding of spring dynamics is of great hydrogeological importance. In this doctoral thesis the Radovna River Valley, located in the north-western Slovenia is selected as a study polygon. The Radovna River is 19.4 km long and almost entirely flows in the area of the Triglav National Park. The Radovna River represents a very interesting and unique research polygon. The reason for this is a different geological structure, in the vicinity and wider recharge area that creates an interaction between karst and porous aquifer. A conceptual hydrogeological model was designed based on this. The depth of the porous aquifer and the shape of pre-Quaternary base were determined. It was found that the groundwater level fluctuates greatly. The water that discharges out of the karst and porous aquifer has different geochemical composition, which is reflected in the river downstream. In addition, stable isotopes in groundwater, in the river, in the precipitation and in the snowmelt were analysed. Mean recharge altitude and the size of the recharge area of the Radovna River were determined. The mean residence times were also calculated. With the isotopic hydrograph separation snowmelt percentages were determined using the two-component model. The percentages of the snowmelt in the discharges represent at least one-third of the total and are decreasing downstream, which means that the water is drained from the lower part of the aquifer, which contains less snowmelt. A great impact on the percentage of snowmelt in the river itself is influenced by the tributaries from both sides of the valley.
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