COBISS: 1.01 TRACING OF THE STREAM FLOwING THROUGH THE CAVE FERRANOVA BUžA, CENTRAL SLOVENIA SLEDENJE POTOKA V JAMI FERRANOVA BUžA NAD VRHNIKO Miha STAUT1 & Primož AUERSPERGER2 Abstract UDC 556.34.04 Miha Staut & Primož Auersperger: Tracing of the stream fow-ing through the cave Ferranova buža, central Slovenia Te article discusses the characteristics of the recently discov-ered ground water stream in the cave Ferranova buža and its possible karstic hydrological system. Its upstream connections have been narrowed to few possible springs by means of logi-cal exclusion and have yet to be confrmed. For the purpose of establishing its linkage to the downstream springs around Vrhnika a water tracing experiment has been performed. Uranine was used as a tracer and sampled in intervals of eight hours at Primc’s spring, Bečkaj’s spring and Kožuh’s spring. Te connec-tion was proved in all three observation points, with Kožuhs spring draining the largest quantity of the tracer. Te tracer ex-periment evidenced that the dye was completely fushed down-ward in single transition curve almost without any retention. keywords: karst, hydrology, water tracing, fuoresceine sodi-um. Izvleček UDK 556.34.04 Miha Staut & Primož Auersperger: Sledenje potoka v jami Ferranova buža nad Vrhniko Prispevek obravnava značilnosti nedavno odkritega podzemnega vodotoka v jami Ferranova buža in njegovega kraškega hidrološkega sistema. Njegove gorvodne povezave so bile zožene na nekaj možnih virov s pomočjo logičnega izločanja. Za potrebe dognanja povezav z dolvodnimi izviri okrog Vrhnike, je bil izveden sledilni poskus. Uporabljeno sledilo je bilo uranin z intervalom vzorčenja na osem ur v Primcovem, Bečkajevem in Kožuhovem izviru. Povezava je bila dokazana z vsemi tremi izviri, vendar se je največja količina sledila pojavila v Kožuhovem izviru. Glede na rezultate sledenja je moč zaključiti, da se je uranin prenesel v enkratnem homogenem valu in da obstaja majhna verjetnost, da se je kje zadržal dlje. ključne besede: kras, hidrologija, vodno sledenje, uranin. INTRODUCTION If a caver asked us what is Ferranova buža like, despite probable sighs from the caving colleagues we would an-swer him, it is a thankful cave. It is not the intention to delve here into the relation that gradually establishes be-tween the cave and its explorer(s). Tat relation is un-doubtedly something special and needs a separate inves-tigation, but would among karstologists probably sound too “personal” and thus un-scientifc. Te intention is to emphasize that afer all the eforts put into it, it always knew how to return the favour with new and new sur-prising discoveries and in that way flled the game with satisfaction that lasts for already more that four years. It presented us with one of those gifs afer one of our clubs meetings when we decided to trace the stream disap-pearing in the terminal siphon of the cave. with the aid of some pretty rudimentary techniques we managed to achieve at frst glance high quality results. 1 Jamarski klub železničar, Hrvatski trg 2, 1000, Ljubljana, e-mail: mihastaut@yahoo.co.uk 2 JP Vodovod-Kanalizacija d.o.o., Vodovodna cesta 90, Ljubljana, e-mail: pauersperger@vo-ka.si Received/Prejeto:14.09.2006 ACTA CARSOLOGICA 35/2, 83–89, LJUBLJANA 2006 MIHA STAUT & PRIMOž AUERSPERGER GENERAL GEOLOGICAL AND HYDROLOGICAL DESCRIPTION Te entrance to Ferranova buža is located about 900 me-tres eastwards from the summit of Ulovka on the eleva-tion 660 m above sea level (a.s.l.). Afer Buser (1968), Ulovka is structured by the Zaplanina nappe, where the upper Triassic dolomites are over-thrusted on the Cre-taceous and Jurassic limestones of Logatec-Cerknica block Limestones outcrop only southwards from the val-ley of Bela and in a narrow strip between Sveta trojica and Ulovka. Te surface of the Ulovka massif is therefore dominated by a weakly expressed karstic morphology with a low drainage density and rare dolines. Te upper part of Ferranova buža evolved in the dolomite along one of the regional faults crossing the Ulovka massif in a dinaric direction. On the depth of 160 m, where the cave signifcantly widens it passes into the limestone which can be traced down to the current bot-tom at 306 m a.s.l. Te narrow upper part of the cave here actually joins a gallery of a completely diferent charac-ter with an active fow that in the direction about 100° passes by (Fig. 1 and Fig. 2). In this second wider part the cave evolved along one or more bedding planes dipping southwards initially under the angle of 40° but towards the bottom steepen up to 70°. with regard to the proxim-ity of the Jurassic limestones it may be deducted that the cave crosses the Zaplanina nappe structure on the junc-tion of the upper and the lower part of the cave. In that respect the cave would be one of the rare known cases of such crossings in Slovenia. showed contamination with faecal bacteria, evidencing that the cave stream is not the consequence of gather-ing of percolating water through the dolomite, such as in the case of the springs Lintvern and Staje (Habič, 1976). Tese two spring from dolomite about 1 km south-west-wards from the entrance of the cave and were used for the Vrhnikas water supply Following the allogenic assumption, the map of sink-ing streams from Rovte hills (Fig. 2), that were predomi-nantly traced into Kožuhs, Primc’s and Bečkajs springs in Vrhnika (Bauer et al, 1976; Habič, 1976; Habič, 1996), indicates possible origins of the water in the cave. Te plan of the cave in Fig. 2 overlaps to some extent with the upper reaches of the stream Korita and is therefore dif-cult to spot. Accounting for the elevation and with regard to the results of extensive water tracing experiments in the catchment of the Ljubljanica river (Bauer et al, 1976), ponors on the Planinsko polje can be excluded as possible sources of the water in the cave as the stream ap-pears in the cave exactly on 500 m a.s.l. (metres above sea level). Te same is true for the Logaščica sinking at about 450 m a.s.l. as well as the Petkovščica. Te later fows into Loška jama with its bottom reaching below the critical depth. Te Hotenjka, the Močilka, the Hlevišarka and the žejska voda were at large traced towards Podroteja and Divje jezero. For the purpose of the Hotenjka tracing the Kožuh spring was sampled for the frst time. Due to its too deep sinking cave it can be excluded similarly stream appearing in the cave —