Gregor Kovačič

Analysis of human induced changes in a karst landscape — the filling of dolines in the Kras plateau, Slovenia

A comprehensive analysis of the increased pressure on karst landscapes due to expansive economic and urban development is presented with the aim of evaluating changes in land use and their deleterious effects on karst relief forms. The study focuses on two areas surrounding the relatively quickly growing settlements of Hrpelje-Kozina and Divača on the Kras plateau (Slovenia) that have been subjected to intensive urban and business development and traffic since the motorway was brought to their vicinity fifteen years ago. National legislation loopholes and technological improvement were the cause of the commonly unsupervised human encroachment which caused the widespread degradation of the landscape. By comparing different topographical and ortophotographical materials from the past four decades and by detailed field inspection of land use and environmental changes, as well as the morphometrical characterization of dolines, the following results have been found: due to the population growth in the past four decades (39% and 50%, respectively), an increase of settlement area by 18 and 11 percentage points took place. Consequently, between 25 and 27% of dolines have disappeared or have been extensively modified (filled up and leveled). According to the local spatial plans, an additional 18% to 28% dolines are endangered. Broad human induced changes in the karst landscape have resulted in a noticeable increase in landscape deterioration, which is consistent with similar phenomena observed in other regions. Due to the extreme susceptibility of the karst to human activities that may lead to the degradation of its exceptional esthetic and environmental value, the alteration of karst processes such as corrosion, endangering of unique habitats and the quality of non-renewable natural resources, it is necessary to promptly define measures for its protection at the national level.

Extreme hydrological events in karst areas of Slovenia, the case of the Unica River basin

The study presents natural hazards in Slovenias karst, focusing on flooding in karst poljes. A specific study was done on the flood dynamics of two typical and connected karst poljes (Cerknica and Planina) of the Classical Karst region. In the case of particularly extreme hydrological conditions in the autumn of 2008, detailed analyses of the recharge-discharge regime and the interrelationship of flooding on the two poljes were done. Daily precipitation, discharge, and water level values from several monitoring sites were analyzed and cross-correlated, and additional hydrological analyses were done using a digital elevation model in order to acquire water level increase and decrease intensity, flood water volumes, and the extent of flooding and to understand the conditions controlling karst flooding. The results reveal that the hydrological functioning of the studied karst poljes is influenced by the hydrogeological and temporary hydrological conditions in the catchment area. The response of the binary karst system (i.e., the influence of autogenic and allogenic recharge) is especially distinct. The study shows that during extremely intense recharge, the reactions of karst aquifer systems to precipitation are as rapid as the response of surface waters (the water level of Cerknica Lake increased with an intensity of 38-63 cm/day or 55 m3/s respectively) while retention capacities are negligible. In contrast to flash floods, floods in karst areas may last from several weeks to several months. For the observed period a three-dimensional simulation of the flooding was made. At the maximum recorded water level, the volume of water on the Cerknica polje was 51 million m3, and 26 million m3 on the Planina polje. The maximum extent of flooding on the Cerknica polje was 23 km2 and on the Planina polje 9.5 km2. On the basis of the study, information was provided regarding future hazard mitigation. However, the study demonstrated that a sufficiently dense monitoring network is necessary to predict the occurrence and duration of floods with greater certainty.

The spatial cognition of Mediterranean in Slovenia: (In)consistency between perception and physical definitions

On the basis of a previously tested method, the cognition of the spatial extent of the Mediterranean in Slovenia is presented. The Mediterranean may be determined on the basis of numerous and very diverse criteria. It is therefore a very subjectively determined notion, where geographical and non-geographical definitions can be treated as equivalent. The research made use of a questionnaire method, which revealed the opinions of the inhabitants living in the area, generally regarded as being Mediterranean. The determination of the Mediterranean was achieved with the aid of a special question. Respondents were asked to graphically delineate its border in Slovenia on a specially prepared general map included in the questionnaire on the basis of their subjective complex perception of the characteristics by them understood as Mediterranean. The questionnaire was spatially structured by the following regions: Slovene Istria, the Vipava Valley, the Vipava Hills, the Goriska ravan, the Brda Hills, the Kras, the Pivka Basin, the Reka Valley, the Brkini Hills and the Matarsko podolje and Ljubljana with its surroundings. By drawing on the fuzzy logic theory and helped by computer techniques all the answers were merged on a special map showing the extent and membership of the fuzzy set “Mediterranean” within the crisp set “Slovenia”. The border between the Mediterranean and non-Mediterranean part of Slovenia is in this way established as a continuous transition. The mean value of this transition goes from Sempeter, passes the eastern flank of Karst, beside Divaca and ends on the eastern side of Slavnik. A more restrictive criterion of the membership function value of 0.95, includes in the Slovenian Mediterranean only the sea and its most immediate hinterland. Particularly interesting proved differences in the spatial cognition of the Mediterranean’s borders in Slovenia between different survey regions.

Application of Methods for Resource and Source Vulnerability Mapping in the Orehek Karst Aquifer, SW Slovenia

In a shallow karst aquifer in SW Slovenia assessment of groundwater and drinking water source vulnerability has been performed using different methods. The small, but well defined, Orehek karst is mainly drained by the no longer exploited Korentan spring. The recharge area of the spring is well karstified, densely wooded, and covered by thin soils. Besides precipitation, the spring is additionally recharged by temporally active sinking streams. To assess the vulnerability, two methods, COP+K and Slovene approach, have been applied. Both methods provide tools for assessing vulnerability in carbonate rocks. They both rank among very sophisticated methods that require vast amounts of data, time, and financial and technical resources. Both methods share the same methodological procedure and consider the same type of information, categorized by the same factors. On the other hand, the scoring, classification and weighting of individual parameters between the methods are different. Consequently, the resulting maps differ significantly. Major differences between the results are identified and discussed. In addition, sensitivity analysis of individual factors have been performed and compared to cross-correlation, autocorrelation and water budget calculations. The results show high dependence of the COP+K method to the parameters characterizing the infiltration conditions (the so-called C factor) and distance to water source. The Slovene approach vulnerability classes are mainly influenced by thickness of the soil cover, presence of morphological features and the temporal hydrological variability that is justified by the performed statistical analysis.

Validation of Vulnerability Assessment Using Time Series Analysis—the Case of the Korentan Spring, SW Slovenia

In the shallow Orehek karst aquifer in southwest Slovenia, the use of hydrological data analysis for the purpose of validating the assessment of water source vulnerability was tested. The appropriate criteria for the aquifer and groundwater flow characterization were identified and major drawbacks highlighted. Results of water budget calculations were used to determine the extent of the catchment of the Korentan spring, which is the main outflow from the aquifer. The vulnerability assessment was verified by autocorrelation and cross-correlation analyses of available daily hydrological time series data. The small variability of the Korentan spring water temperature and electric conductivity time series points to the dominance of autogenic recharge and that sinking streams in the catchment contribute to the spring to a minor degree. The analysis indicated relatively small storage capacity of the aquifer and its high degree of karstification and rapid groundwater flow. The results justify the small proportion of highly vulnerable areas and lower vulnerability for marginal parts of the aquifer. Time series analyses proved to be time- and cost-effective, but have limited applicability for vulnerability validation purposes, as they do not provide direct and clear spatially resolved information on the vulnerability of the catchment.

Vulnerability and protection aspects of some Dinaric karst aquifers: a synthesis

The present paper aims to address the sustainable management issues of karst water sources in Slovenia and Croatia. It focuses on the Mediterranean part of the Dinaric karst, which holds important groundwater reserves. The importance of selected karst aquifers for water supply is presented. In addition, national drinking water management strategies are examined to synthesise the issues relating to the exposure of groundwater to contamination and over-exploitation. Finally, the most significant problems, pressing needs and challenges are identified. These depend predominantly on revision of existing drinking water protection strategies and integration of karst-specific provisions, aspects of over-exploitation and proper water quality control. The need for harmonised multi-country policies regulating resource abstraction and contamination issues is stressed.

Abandoned water resources as potential sources of drinking water – the Korentan karst spring near Postojna

In the area of the Orehek karst intrinsic vulnerability maps of groundwater and the Korentan karst spring, hazard maps and risk to contamination map have been made using Slovene Approach. For this purpose cartographic and other published data on geological, geomorphological, pedological, hydrological and meteorological characteristics have been gathered and extensive field inventory of the missing geomorphological and pedological characteristics has been made. Publically available land use and census data have been examined and checked in the field, manure heaps and illegal waste dumps have been mapped. The final thematic maps are excellent tools for national and local authorities when planning water protection and land use. The presented study in the catchment of an actual water source is an example of good practice of the revival of the in the past abandoned water sources that can in the future serve as a substitution water source in case of main water source overexploitation or contamination.

Flooding in the area of Knežak, Bač and Koritnice in November 2000

In November 2000 a flood occurred in karst polje between the settlements Bac, Knežak and Koritnice in the municipality of Ilirska Bistrica. The continuous surface of the flood extended to 59 hectares. The flood mostly affected Bac, where 23 residential and some other buildings, an industrial facility and road infrastructure suffered damage.

Vpliv podnebnih sprememb na količine vode in poplave morja v slovenski Istri // Climate change impacts on water quantities and sea flooding in Slovene Istria

V prispevku so obravnavane pretocne razmere rek v slovenski Istri in dvigovanje gladine morja. Z uporabo Senovega naklona smo v slovenski Istri potrdili statisticno znacilna trenda povecevanja skupne letne visine izhlapevanja 49 mm/desetletje in narascanja povprecne letne temperature zraka 0,53 o C/desetletje. Statisticno znacilnega zmanjsevanja skupne letne visine padavin nismo potrdili. Omenjeni dejavniki podnebnih sprememb, skupaj z drugimi spremembami v okolju, vplivajo na zmanjsevanje srednjih letnih pretokov rek v slovenski Istri 40–80 l/s na desetletje, a trendi niso statisticno znacilni. Padajoci trend za reko Rižano je z vidika oskrbe obalnih obcin s pitno vodo zelo zaskrbljujoc. Trend zvisevanja srednje gladine morja (4,5 mm/desetletje) ni statisticno znacilen. Analiza je pokazala, da bi bilo ob dvigu gladine morja za 1 m poplavljenih 848 zgradb in ogroženih približno 3800 prebivalcev (najvec v Kopru). The article deals with discharge characteristics of rivers in Slovene Istria and with the rising of the sea level. Using the non-parametric Sen’s slope test statistically significant trends of increasing annual potential evapotranspiration (49 mm per decade) and increasing mean annual air temperature (0.53°C per decade) were determined. Statistically significant decreasing of annual precipitation was not determined. These climate change factors, together with some other environmental changes, are reflected in decreasing of mean annual discharges of the rivers in Slovene Istria with the intensity of 40-80 l/s per decade, but the trends are not statistically significant. Decreasing trend of the Rižana river is problematic in terms of water supply in the region. Increasing trend of maximum sea level (4.5 mm per decade) is not statistically significant. Analysis showed that a total of 848 buildings would be flooded, and a total of around 3,800 people would be at risk (the majority of whom are living in Koper) if the sea level would increase by 1 m.

Relief evolution in the hinterland of the Pivka river

The article discusses relief evolution in the catchment area of the highest situated permanent spring of the Pivka river – the Pivsce karst spring near the village Zagorje. The discussed landscape, which lies on the southernmost edge of the Upper Pivka valley, shows several geomorphological particularities, which are the result of different geomorphogenetic processes in the past. The basic characteristics of the present relief were shaped in the Pliocene when also the original valley of the Pivka river was formed. The region was more profoundly transformed by Pleistocene processes, which strongly altered the surface. Apart from karstic relief forms, there are several small dry stream channels on the land surface, which were carved by torrents. The two most distinctive relief features are the karst polje situated between the villages Koritnice, Bac and Knežak, which is covered with rubble and gravel-like clastic sediments, and the dry valley of the former Pivka river lying southwest from Koritnice.