Recent results of tracer tests in the catchment of the Unica River (SN Slovenia) In the catchment area of the Unica River two combined tracer tests with fluorescent dyes have been performed aiming to characterize the properties of groundwater flow and transport of contaminants through the vadose zone and well developed system of karst channels in the epiphreatic and phreatic zone in different hydrologic conditions. Tracers were injected directly into the ponors and to the oil collector outlet on the karst surface. Prior to tracing monitoring network has been set up, including precipitation, physical and chemical parameters of the springs and cave streams. Field fluorimeters were used to detect tracers in the underground river and conventional sampling techniques and laboratory analyses were used at the springs. Some of the results were quantitatively evaluated by QTRAC-ER2 Program. During the first tracer test, when injection was followed by rain event, flow through the well conductive cave system was characterized by apparent dominant flow velocities of 88-640 m/h. Breakthrough curves were continuous, uniform and single peaked, and almost complete recoveries were observed. During the second tracer test, when water level was in constant recession, the transport velocities through the well developed karst conduits were significantly slower (apparent maximal flow velocities being 2-4 times lower). Results also show lower dispersivity during the second tracer test, which corresponds to lower flow velocities. The tracer injected at the karst surface arrived with the expected delay (v dom around 9 m/h) and showed irregular and elongated breakthrough curves with secondary peaks. In this paper only tracer test results are presented, which are a part of a comprehensive study of groundwater flow through the complex karst aquifers aiming at improving karst water resources understanding, protection and management. The presented assessment will beyond be utilized for further detailed analysis, studies and modelling.

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Izvleček UDK 556.33(497.4) Gregor Kovačič: Hidrogeološka študija kraškega izvira Malenščica (JZ Slovenija) z metodo analize časovnih vrst Kraški vodonosniki se pogosto preučujejo z uporabo metode analize časovni� vrst, vendar so raziskave, ki vključujejo veliko število prostorsko razporejeni� časovni� vrst, zelo redke. Raziskave, ki poleg padavin, vodostajev in pretokov vključujejo tudi druge tipe �idrološki� časovni� vrst, so prav tako redke. Predstavljena raziskava vodonosnika kraškega izvira Malenščica poudarja uporabnost �kratne avtokorelacijske in križnokorelacijske analize različni� dnevni� in urni� �idrološki� časovni� vrst, kot so pretoki, vodostaji, temperature, specifična električna prevodnost in padavine na regionalnem nivoju. Rezultati avtokorelacijske analize kažejo, da je skladiščna zmogljivost izvira Malenščica srednja, kar ne kaže na slabšo zakraselost sistema, ki ga označuje prevladujoča kanalska prevodnost. To nakazuje, da imajo la�ko dobro zakraseli sistemi kompleksnejše zgradbe daljši spominski učinek kot dobro zakraseli sistemi enostavnejše �idrogeološke zgradbe. Rezultati križnokorelacijske analize kažejo, da kraški izviri in vodotoki na preučevanem območju na precej �omogene padavine reagirajo �itro in �krati, vendar pa različno intenzivno. V taki� primeri� iz križnokorelacijske analize med padavinami ali pretoki kot vnosi ter izviri kot iznosi iz sistema ni mogoče dobiti zadovoljivi� informacij o �idrogeološkem delovanju sistema, medtem ko rezultati križnokorelacijske analize časovne vrste specifične električne prevodnosti dajejo koristne informacije o njegovem delovanju in ji� la�ko preprosto primerjamo z rezultati sledilni� poizkusov. Pri kompleksni� kraški� sistemi� kaže časovna vrsta temperatur omejene možnosti uporabe. Primerjalna analiza rezultatov analize časovni� vrst med zaporednimi �idrološkimi leti je pokazala, da na rezultate navedene analize močno vpliva izbira preučevanega �idrološkega leta.

Izvleček UDK 556.3(497.4 Cerknica) Gregor Kovačič: Poskus ocene vodne bilance Cerkniškega polja V članku je predstavljena vodna bilanca Cerkniškega polja. Rezultati predhodnih raziskav so primerjani z izračuni dotokov in odtokov s polja v hidrološkem letu 1975 (411 dni). Izračun vodne bilance Cerkniškega polja je narejen na osnovi dnevnih sprememb prostornin Cerkniškega jezera, izračunanih s pomočjo podatkov o vodostajih Stržena na vodomerni postaji Dolenje Jezero in digitalnega modela višin Cerkniškega polja (velikost celic 25 x 25 m). Za preučevano leto je skupen odtok s hidrološkega zaledja Cerkniškega polja (475 km 2) ocenjen na 620 milijonov m 3 vode oziroma 17 m 3 /s. V hidrološkem letu 1975 je največje naraščanje prostornine jezera, preračunano v pretok, znašalo 135 m 3 /s, medtem ko je največje zmanjšanje prostornine jezera znašalo 60 m 3 /s. Največji možni dotok na Cerkniško polje je izračunan na 232 m 3 /s. V hidrološkem letu 1975 je povprečni odtok s Cerkniškega polja skozi ponorne jame in talne ponore znašal 23,69 m 3 /s, izračunani največji pa 91,7 m 3 /s. Ključne besede: Cerkniško polje, kraška hidrologija, vodna bilanca, kraški odtok, Cerkniško jezero.

The study presents natural hazards in Slovenia's 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 m 3 /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 m 3 , and 26 million m 3 on the Planina polje. The maximum extent of flooding on the Cerknica polje was 23 km 2 and on the Planina polje 9.5 km 2 . 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.