Metka Petrič

Development of a Protocol for the Karst Water Source Protection Zoning: Application to the Classical Karst Region (NE Italy and SW Slovenia)

Although karst aquifers are highly vulnerable and represent an important water resource, they are often inadequately protected. Furthermore, national water resource protection policies lack precision regarding the criteria for delimitation of source protection zones in karst. Usually either vulnerability assessment or travel time is considered. The proposed integrated protocol considers both. It is specifically designed for large karst aquifers where i) an additional distinction between areas of different liability to contamination within the aquifer, and ii) a certain generalisation of protection classes should be made for practical reasons. The protocol includes a detailed description of the separate steps of the protection zoning procedure. Information obtained from both artificial and natural tracers is used to account for the variability of groundwater flow under different hydrologic conditions. Analysis of groundwater physico-chemical parameters time series is better employed under high flow regimes and analysis of artificial tracers breakthrough curves under low flow conditions. Source protection zones are divided into three levels of protection, which should be further generalised, validated and adjusted to land use plans. The protocol has been applied to the Classical Karst Region transboundary aquifer (NE Italy and SW Slovenia). The results enable a uniform delineation of protection zones encompassing water sources that have not been protected to date, and improve the understanding and management of transboundary aquifers. The proposed protocol can be used in other karst aquifers, and adjusted to national protection legislation and spatial planning frameworks.

Integration of models of various types of aquifers for water quality management in the transboundary area of the Soča/Isonzo river basin (Slovenia/Italy)

Due to intrinsic characteristics of aquifers groundwater frequently passes between various types of aquifers without hindrance. The complex connection of underground water paths enables flow regardless of administrative boundaries. This can cause problems in water resources management. Numerical modelling is an important tool for the understanding, interpretation and management of aquifers. Useful and reliable methods of numerical modelling differ with regard to the type of aquifer, but their connections in a single hydrodynamic model are rare. The purpose of this study was to connect different models into an integrated system that enables determination of water travel time from the point of contamination to water sources. The worst-case scenario is considered. The system was applied in the Soča/Isonzo basin, a transboundary river in Slovenia and Italy, where there is a complex contact of karst and intergranular aquifers and surface flows over bedrock with low permeability. Time cell models were first elaborated separately for individual hydrogeological units. These were the result of numerical hydrological modelling (intergranular aquifer and surface flow) or complex GIS analysis taking into account the vulnerability map and tracer tests results (karst aquifer). The obtained cellular models present the basis of a contamination early-warning system, since it allows an estimation when contaminants can be expected to appear, and in which water sources. The system proves that the contaminants spread rapidly through karst aquifers and via surface flows, and more slowly through intergranular aquifers. For this reason, karst water sources are more at risk from one-off contamination incidents, while water sources in intergranular aquifers are more at risk in cases of long-term contamination. The system that has been developed is the basis for a single system of protection, action and quality monitoring in the areas of complex aquifer systems within or on the borders of administrative units.

Caves and Hydrology of the Contact Karst of Beka and Ocizla

The Beka-Ocizla cave system extends at the contact between Palaeocene limestone and Eocene flysch at an altitude of 350 m in a shallow depression called Loke. Six known caves are connected to this cave system: Ocizeljska jama (Ocizla cave), Blažev spodmol (Blaž’s rock shelter), Maletova jama s slapom (Maletova jama cave with waterfall), Jama z naravnim mostom (Cave with the natural bridge), Jurjeva jama v Lokah (Jurjeva jama cave in Loke) and S-4/Socerb. Three larger streams and a smaller one flow into the depression from flysch and sink into marly limestone. Together, they drain the flysch surface of approximately 3.5 km2. Some of the cave entrances function as periodic sinks of the surface waters that flow in from beneath the villages of Beka, Ocizla and Petrinje. The water from the entire cave system flows towards the Boljunec spring. Hydrological observations conducted in the cave include mapping of traces of the past flood events and continuous monitoring of the water level and temperature at five different locations in the cave system. A few flood events happened in past years: an extreme flood event between 17 and 19 September 2010, and flood events between October 2012 and March 2013. Special hydrological conditions during these events are also described.