Abstract 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 of c. 60 mm decade −1 and 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 of c. 480 l s −1 decade −1 with 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.

Movement of the Adria microplate is one of the main elements for understanding crustal deformations in the central Mediterranean and central Europe. To study present-day tectonics in Adria and the nature of its boundary relative to those of the Africa and Eurasia plates, three GPS (Global Positioning System) campaigns involving 41 stations were carried out within CRODYN (the Croatian and Slovene Geodynamic Network). Movement of stations derived in the International Terrestrial Reference Frame 1996 (ITRF96) with respect to the permanent ITRF/IGS (International GPS Service) station GRAZ in Austria, located north of the network, and values of the principal strain rates determined on the basis of analytical surface deformation theory suggest that Adria is divided into three different deformation zones (northern, central, and southern). The domain of northeastern Italy moves 5 mm/yr in an east-northeast direction. The stations in southwestern Slovenia move 3–7 mm/yr in a north-northwest direction, whereas those in southern and northeastern Istria move 4–5 mm/yr in a more easterly direction. The greatest movement (8–10 mm/yr) occurs in central Adria between the Gargano zone and the central Dinarides; there, the movement is northeast-oriented. A fragmentation of Adria into subblocks linking the Gragano zone to the central Dinarides cannot be clearly demonstrated. The southeastern part of Adria, along the coastline of Albania, moves 5–7 mm/yr in an almost east-west direction, and eastern Albania moves 6 mm/yr in an east-southeast direction. The permanent ITRF/IGS stations POTS and WTZR in Germany, BOR1 in Poland, and PENC in Hungary demonstrate no significant movement. The movement of the stations discussed here differs very clearly from the known north-west motion of the Africa plate and suggests that Adria is an independent microplate.