Previous studies suggest a hydrogeologic link between the Vipava springs and the neighbouring Bela surface stream. The Vipava springs drain the Nanos karst plateau. The Bela stream drains the very ...low permeable flysch to the north west of the Nanos plateau before flowing onto limestone where it gradually sinks along its course. A tracer, uranine, was injected into the Bela upstream of the village Vrhpolje and hydraulic connection with all the Vipava springs was proved. A dispersion model was used to characterise the tracer breakthrough curve of one of the springs where the highest concentrations were found. The hydrology of the Bela was analysed by measuring the discharge of the stream at 8 different sections and analysing the difference in flow between each section. The conclusion drawn from the analysis was that the Bela stream has a different hydrological response related to whether the majority of recharge comes from the karstic or flysch area of the catchment. A flow separation analysis based on hydrochemical measurements indicated that the hydrological response of the Vipava springs also depends on the recharge source area. Proved connection leads to environmental concern for the water quality of the Vipava springs, which are the main water supply of the area, because untreated wastewater is discharged into the Bela stream.
For the karst aquifer in the background of the Vipava springs in south-western Slovenia the first the model of the recharge estimation was set on the base of the method of soil moisture balance. ...Additional to precipitation, the influences of the interception on vegetation cover, snow and snowmelt, evapotranspiration, water storage in soil, rapid recharge and secondary infiltration were also considered in this model. It was calibrated by comparison with the discharges of the Vipava springs and then the daily values of recharge were estimated. To test the role of such accurate estimation of the recharge in further hydrodynamic analysis of karst aquifers, the black-box method was used. As the input signal in the supposed linear system the measured precipitation was first adopted, and then the estimated recharge values. It was demonstrated by comparison of results that the introduction of the recharge function significantly improves the model. In this way the important influence of the processes in the air, vegetation and soil on the amount and the time distribution of the recharge, and through this also on the hydrodynamic functioning of karst aquifers, was proved.
