Karst aquifers hold important water resources such as regional water budgets and freshwater supply. Due to highly dynamic hydrological processes in comparison to other less permeable systems, they are particularly susceptible to environmental changes. However, little research directly characterizes the impacts of climate and vegetation cover changes on karst water sources. In this study, we aimed to evaluate individual long-term impacts and impacts of sudden large-scale forest disturbances on changes in groundwater recharge and in spring discharge. The work is based on temporal analysis of forest cover and a comparison of trend analysis of hydro-meteorological parameters. To investigate and evaluate vegetation cover change impacts on groundwater recharge, we used a soil water balance model and compared estimated actual daily values of effective precipitation to its fictional estimation disregarding the vegetation cover change. The applied methodology enabled quantification of the impacts of climate and vegetation cover change on selected karst water sources. The study suggests that the vegetation cover can have a significant impact on the spring recharge. Large-scale disturbances that occurred in a short-term mitigated the effects expected from the trend analysis of hydro-meteorological parameters. In the long-term, in addition to climate changes, the multi-decadal natural vegetation overgrowth significantly contributed to the reduction in the spring’s discharge values, especially in the warm season when water demand is higher. Therefore, the results are of key importance for developing proper water management and environmental policies.

V prispevku so obravnavani trendi značilnih letnih in mesečnih pretokov rek jadranskega povodja v Sloveniji brez Posočja. Z uporabo Senovega naklona smo potrdili statistično značilne trende: zmanjševanje skupne letne višine padavin 36–61 mm/desetletje, naraščanje povprečne letne temperature zraka 0,32–0,34 oC/desetletje ter povečevanje skupne letne višine izhlapevanja 29–49 mm/desetletje. Omenjeni dejavniki podnebnih sprememb vplivajo na zmanjševanje srednjih letnih pretokov Rižane, Badaševice, Drnice, Dragonje in Reke na vodomerni postaji Cerkvenikov mlin. Padajoči trend je statistično značilen zgolj za Rižano (480 l/s na desetletje) in Dragonjo (160 l/s na desetletje). Naraščajoča trenda srednjega letnega pretoka Reke na vodomerni postaji Trnovo (360 l/s na desetletje) in Bistrice (60 l/s na desetletje) nista statistično značilna.The article deals with trends in characteristic annual and monthly discharges of the Adriatic Sea basin rivers in Slovenia, excluding the Soča river basin. Using the non-parametric Sen’s slope test, statistically significant trends were determined for: i) decreasing annual precipitation (36–61 mm per decade); ii) increasing mean annual air temperature (0.32–0.34oC per decade); and iii) increasing annual evapotranspiration (29-49 mm per decade). These climate change factors are reflected in decreasing mean annual discharges of the Rižana, Badaševica, Drnica, Dragonja and Reka (the Cerkvenikov mlin gauging station) rivers. The decreasing trend is statistically significant only for the Rižana (480 l/s per decade) and the Dragonja (160 l/s per decade) rivers. The increasing trends in the mean annual discharge of the Reka river at the Trnovo gauging station (360 l/s per decade) and of the Bistrica river (60 l/s per decade) are not statistically significant.

The behaviour of aquifers with karst porosity is dependent on hydrological conditions. This is due to the peculiar characteristics of the groundwater flow and dynamics of hydrological processes in karst. As a result, karst aquifers are especially vulnerable to the effects of environmental change. We assessed the long-term climatological and hydrological trends and the short-term effects of increasingly frequent extreme hydrological events (droughts) for the Mediterranean karst spring Rižana in SW Slovenia. The findings predict higher mean annual air temperatures of 0.34°C decade⁻¹, lower annual precipitation ofc.60 mm decade⁻¹and higher annual actual evapotranspiration (especially during spring and summer) of 32–49 mm decade⁻¹. As a consequence, we can expect a decrease in the mean annual discharge of the spring ofc.480 l s⁻¹decade⁻¹with prolonged dry summer periods. Detailed monitoring of the physical, chemical and microbiological parameters showed that the flood pulses caused by precipitation events after a long dry period cause a significant deterioration in water quality. In such situations, contaminants stored in the unsaturated zone are flushed out and counts of coliform bacteria can reach >1400 cfu (100 ml)⁻¹, with total Al and Fe concentrations up to 206 and 474 μg l⁻¹, respectively. These results suggest that there should be urgent adherence to water quality standards to protect karst water sources in view of the anticipated climatological stresses. Management strategies should promote monitoring and the rational use of karst water supplies.

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 Goriška 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 Šempeter, passes the eastern flank of Karst, beside Divača 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.