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Photo FP6.1. (left).
Map showing the location of "Pasmica" Ponor in Fatničko Polje.

This is the most significant single ponor within Fatničko Polje. It is situated in the lowest part of the polje in its south-east corner below and to the north-west of the village of Pađeni, at an elevation of  462.5 m. asl.
Interestingly, it has been reported that this ponor is situated at an elevation which is 2 metres higher than that of the natural lip of Estavela "Obod" !!
[NB. We cannot measure the elevation of the natural lip of Estavela "Obod", which is buried below the structure of the estavelle Dam.]

Description of the Surface Feature

Photo FP6.1. (above-left). (Photo :  Bogdan Prelević, 11 November 2001.  Digital Sony FD71.)
A view of the Pasmica Ponor and its doline in the Lower Polje area. The standing figure near the edge of the ponor mouth to the left in the view, is dwarfed by the karst feature.
The true thickness of the sediment cover in the ponor zone is evident in this image.
Photo FP6.2.  (above-right)..(Photo :  B. Lewarne, 05 March 2002.  Digital Sony FD92.)
A view of the ponor from the south, with the dry stream-bed coming in from the top-left of the image (west).
In both photographs, note the old and deteriorating dry stone walls, previously constructed to keep the mouth of the ponor open to facilitate drainage.

Photo FP6.3.  (Photo :  B. Lewarne, 05 March 2002.  Digital Sony FD92.)
A view of an alluvial doline and sinkhole in the immediate vicinity of "Pasmica" Ponor, with the ponor's approach streamway and Hydrometric Weir in the background.
Photo FP6.4.  (Photo :  B. Lewarne, 05 March 2002.  Digital Sony FD92.)
A view of the "Pasmica" Ponor mouth.

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Surface Hydrometric Infrastructure

Photo FP6.5. (left).(Photo :  B. Lewarne, 05 March 2002.  Digital Sony FD92.)
A view of the stream-guage weir structure across the entire approach stream-bed, a few hundred metres upstream of the "Pasmica" Ponor.
Measured constructional details of this weir will be given below. The weir seemed to be in a reasonable and operational condition, although in some need of essential maintenance.
The device becomes totally inundated during even minor polje flooding events.
 

Details of the interior entrance series of cave passages are given in plan and cross-sectional diagrams in an attached Bitmap via the Link below.
 

.....Click on the.Link to see...*...the Constructional Details of the "Pasmica" Ponor Stream-guage Weir.
 
 

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Description of the Ponor Cave System
 
 
 
 
 
 
 
 
 
 
 
 

Photo FP6.8.  (left).  (Photo :  B. Lewarne, 05 March 2002.  Digital Sony FD92.)
Another view of the entrance mouth of "Pasmica" Ponor.

DETAILS OF THE GEO BOMB METHOD OF INVESTIGATION :
In 1969, the Geo Bomb Method was a completely new and special seismic method of testing for the karst researchers in Yugoslavia. The method was particularly adjusted for investigations of locations of the underground water courses in karst. Arandjelovic initiated the development of this method, which was based on the hypothesis that through karst channels with flow capacities of several cubic metres per second, an activated Geo Bomb of spherical shape and with the same specific gravity as that of water, could travel long distances. With this being the case and with the Geo Bomb containing enough explosive to produce an elastic wave, which could be easily detectable on the karst terrain above, the location of the karst channel it was travelling in could be determined.

Thus, a Geo Bomb of 15 cm diameter containing about 930 g of plastic explosive was designed. It incorporated a detonator and an electric battery connected to a timer for detonation accurate to within 10-15 seconds within a 2 hour period after setup.
On the surface, sets of geophones, orientated perpendicular to each other, were used to detect the explosion. They were connected to seismographs.
In Fatničko Polje, 24 sets of geophones were connected to a 24 channel seismograph, located in a vehicle. Above the "Pasmica" Ponor, a tower-frame was constructed in the dry period. (see Photo 6.3. below). This was to assist with the insertion of the Geo Bomb into the mouth of the ponor during the period of flooding. (see Photo 6.2. below.)
Prior to the time of their insertion, the Geo Bombs were filled with explosives, weighed and activated with detonators. The Bombs were then inserted into "Pasmica" Ponor carried by the water flow until their activation.

The propagation of the elastic waves created by the explosions was measured on chart paper in the seismograph. The results were very clear and by calculating the results thus obtained, the exact location of the explosion points determined the position of the underground passages of "Pasmica" where and when the explosions took place.

Photo FP6.6. (above). (after  Milanović 1979 and 1981.  Digitally reproduced from a Lithograph.)
Preparing a Geo Bomb for insertion into the submerged mouth of the "Pasmica" Ponor, 1974.
 
 
 
 

Photo FP6.7.  (left).   (after Milanović 1979 and 1981.  Digitally reproduced from a Lithograph.)
Preparing a tower in the mouth of the "Pasmica" Ponor during the dry season in 1974, in readiness for
the insertion of Geo Bombs during the wet season, to enable detection of the location of the underground
karst channels by seismic methods.
The inset is a view of "Pasmica" Ponor from a distance, with Fatničko Polje in the background.
 
 
 
 

The Society's brief reconaissance to the "Pasmica" Ponor with Members of the Speleološko Društvo "Zelena Brda" in early March 2002 has given an opportunity to record this magnificent karst feature in greater detail.
In the view Photo FP6.8. in the left margin, the team can be seen free-climbing up and out of the ponor-mouth.

Click on the Link to see.. *...Plan and Longitudinal section of the "Pasmica" Ponor Entrance Series.

We cannot yet publish images of the ponor-system's cave passages in the Entrance Series.

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Hydrological Characteristics

.....6.3.2.  Established Underground Flowline Data :
All data collected so far would seem to indicate that this Ponor drains exclusively to the underground catchment of the Trebišnjica Spring Group (Vrelo "Trebišnjica" & Vrelo "Čepelica"), a straight-line surface distance of 17.2 km., and that it makes no contribution to the surface or underground catchment of the Bregava Springs.
 

a)..Date of Test  =  01 January 1955. Method  = Na-fluorescein. Sinkhole Condition  = Inundated 2.20 m. water Water Velocity (sink to rising)  = 7.42 cm sec -¹. Connection  = with Vrelo Trebišnjica at Bileća. No. of Observation Points  = ? Quantity of Tracer  = 56 kg.	c)..Date of Test  =  27 November 1958. Method  = Na-fluorescein. Sinkhole Condition  = Inundated 9.22 m. water Water Velocity (sink to rising)  = 14.1 cm sec -¹. Connection  = with Trebišnjica / Čepelica Karst Springs at Bileća. No. of Observation Points  = 25. Quantity of Tracer  = 150 kg.
b)..Date of Test  =  27 November 1958. Method  = Na-fluorescein. Sinkhole Condition  = Water Velocity (sink to rising)  = 7.42 cm sec -¹. Connection  = with Trebišnjica Karst Spring at Bileća. No. of Observation Points  = Quantity of Tracer  = ?	d)..Date of Test  = 1959. Method  = Na-fluorescein. Sinkhole Condition  = Inundated 9.56 m. water Water Velocity (sink to rising)  = 10.9 cm sec -¹. Connection  = with Trebišnjica / Čepelica Karst Springs at Bileća. No. of Observation Points  = ? Quantity of Tracer  = 117 kg.