STADLER, Ph. & HÄUSLER, H. (2012): Isotope hydrology reveals a fissured aquifer in the karst of Gorski Kotar. The Zeleni Vir case study (Outer Dinarides, Western Croatia).- Geophysical Research Abstracts, Vol. 14, EGU2012-5904, EGU General Assembly, 2012, Vienna.
- Author(s)
- Hermann Häusler
- Abstract
Zeleni Vir is a small village in Western Croatia located at an altitude of 303 m. It is situated at the junction of two small rivulets, namely the Zeleni Vir Rivulet and the Klamm Rivulet. A steep road leads to the village of Skrad, located at an altitude of about 750 m, which is situated on the foot hills of Skradski vrh (1043 m). About 8 km to the south, the village of Ravna Gora borders the highway Zagreb-Rijeka at an altitude of 800 m. The sedimentary rocks of Gorski Kotar comprise Permian sandstone, Triassic dolomite and Jurassic limestone. The Jurassic limestone at the base (karst floor 1) was overthrusted by Permian sandstones, which are overlain by Triassic dolomites (karst floor 2). Based on this tectonic concept we conclude that the recharge area for the upper karst floor 2 is situated around Skradski vrh, whereas the recharge area for the lower karst floor can be assumed around the ponors of Ravna Gora.
In summer 2010 the discharge of the Zeleni Vir Rivulet was 200 l/s, charged by wells from the Triassic karst aquifer of Skradski vrh (karst floor 2), the water of which falls down the steep rock walls above Zeleni Vir Cave. It is characterized by an electric conductivity of about 300 MyS/cm, and a O-18 value of -10,30‰. The discharge of the Klamm Rivulet was 50 l/s, charged from a catchment comprising Permian sandstones, and therefore its electric conductivity was about 100 MyS/cm only. Its stable isotope value with O-18 = -10,10‰ was slightly higher compared to that of the Zeleni Vir Rivulet.
Midst of June 2010 a heavy thunderstorm from Rijeka Bay shifted rain clouds towards the Gorski Kotar, and two precipitation events, the first on 15 June and the second on 16 June, were rich in heavier isotopes (O-18 = -5,50‰). Due to the fact that all water discharging in the Zeleni Vir Cave was diverted to a hydro power scheme, no karst water from karst floor 1 contributed the Zeleni Vir Rivulet. The hydrograph of the Zeleni Vir- and Klamm Rivulet rapidly increased after each of these two precipitation events, and the heavier isotope signal clearly overprinted the previous isotope composition of the streams. The discharge of both rivulets increased up to 150-200 l/s but their flow dynamics differed.
After each of the two rainfall events the discharge of the Zeleni Vir Rivulet rapidly increased up to 400 l/s, but rapidly decreased again to its former flow. This flow dynamics indicates a rapid surface run off of precipitation water, and therefore we exclude the discharge of karst water from karst floor 2 during the monitoring time of 48 hours. During the same two precipitation events the discharge of the Klamm Rivulet also increased rapidly twice up to 200 l/s, but its discharge decreased moderately. We interpret this relatively slow decrease of discharge as the result of a piston flow effect, retarded by a porous aquifer of the weathered sandstones in its catchment.
- Organisation(s)
- Publication date
- 2012
- Austrian Fields of Science 2012
- 105303 Hydrogeology
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/1b54d768-8d56-4392-93f4-598ad461bf46