Many studies related to groundwater flow in karst aquifers are made based on observations at ponors and karst springs. Due to different limitations such as the difficulty of accessibility or a speleologically poorly investigated area, water active caves are usually not monitored.
A network of autonomous measurements in the aquifer between Planinsko Polje and springs of the Ljubljanica River has been established since 2015. There, water level, temperature, and specific electrical conductivity are measured at the main ponors, springs and most of the caves with an access to the groundwater. The obtained measurements were supported by geological, speleological and meteorological data and were comprehensively analysed considering basic hydraulic principles and previously knowledge of the studied system. Interpretations were integrated by constructing conceptual hydrological models that were verified with simplified but robust numerical models.
The water level showed various dynamics, which not only resulted from the last rain event, but also from the geometry of the epiphreatic zone. Inflection points were visible in the hydrographs at almost all locations and reflected the presence of overflow channels. In addition, major geological structures have been identified to control the direction of the groundwater flow and to cause backflooding/damming of water. Temperature and conductivity measurements were used as potential tracers and enabled the calculations of transit times between consecutive points.
The developed approach turned out to be very useful to characterize the aquifer main flow dynamics. It also showed that water active caves are a very important element that should be integrated as much as possible in the observation network. Numerical models proved to be meaningful to verify qualitative interpretations made by the conceptual hydrological models. Additional improvements using a denser observation network would allow a more detailed interpretation of the system behaviour.