The Devon Karst Research Society & Speleološko Društvo "Zelena Brda"
Istočna Hercegovina, Bosna i Hercegovina.
Источна Херцеговина, Босна и Херцеговина,
FATNIČKO POLJE  -  ФАТНИЧКО ПОЉЕ
Fatnica Polje, Eastern Herzegovina, Bosnia & Herzegovina.
updated 30 October 2009.
[under construction with the complete text being added over the coming months.]


Section 2.0.    KARST HYDROLOGY & HYDROGEOLOGY  -  HIDROLOGIJA i HIDROGEOLOGIJA KARSTA
-  ХИДРОЛОГИЈА и ХИДРОГЕОЛОГИЈА КАРСТА :
Link Page for
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DEJANOVA PEĆINA  -  DEJAN'S CAVE  -   ДЕЈАНОВА ПЕЋИНА
The karst spring group of the River Trebišnjica and its adjacent surroundings are relevant to the overall study of Fatničko Polje because together they form the area of the principal local base-level of erosion for the Polje. This Link Page for the karst hydrology and hydrogeology of Fatničko Polje provides details of the Trebišnjica Karst Spring Group when it was visible and fully accessible, prior to inundation by the HET Company's Bileća Lake in the 1960's. The spring group is currently situated 75 metres below the surface of the HET Company's Bileća Lake. Dejanova.Pećina was the principal outlet of this massive and impressive spring group and as such, forms the main subject of this subsidiary Webpage. Palaeo-hydrographic interpretations of its immediate environs are also provided on this page, together with the functionality of other spring-cave components within the Trebišnjica Karst Spring Group.
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Image FP-DjP.000. (above-left) :
This is an historical or contemporary images of the cave entrance of Dejanova Pećina, dated 1890. It is of Austro-Hungarian origin. We have also located one lithographic line drawing of the external entrance area in which women can be seen washing clothes in the karst spring water. This drawing can be seen opposite in Image FP-DjP0. Compare the details of the line drawing opposite with those in the image on the left. 
Image FP-DjP.00. (above-right) :
This is a photograph of the cave entrance area prior to the final flooding of the area and the creation of the HET Company's Bileća Lake.
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Image FP-DjP0.
"At the Source of the Trebišnjica near Bileća, ca. 1900."
(source unknown)
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Image FP-DjP.1. (left) :
This is an old photograph of the cave entrance area of unknown date and origin. 
It was probably recorded before the one at top-left,
insofar as the little footbridge in the view below is not in such a developed condition.
Bushes conceal the low-flow conditions of the outflow.
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"ДЕЈАНОВА ПЕЋИНА - Спелеолошка и хидролошка испитивања на врелу Требишњице."
["DEJANOVA CAVE - Speleological and Hydrological Investigation of the Trebišnjica Karst Spring."]

The extensive information about this karst spring cave given below, is archive material, written by Dragutin Petrović in his Article "ДЕЈАНОВА ПЕЋИНА - Спелеолошка и хидролошка испитивања на врелу Требишњице." - ["DEJANOVA CAVE" - Speleological and Hydrological Investigation of the Trebišnjica Karst Spring"], published in the journal series Zbornik radova Instituta za proučavanje krša "Jovan Cvijić" Knj. 1. (1955). This can be downloaded as a .pdf by clicking on the following Link.ДЕЈАНОВА ПЕЋИНА.
The language of the publication is pre-standardized Serbian from which we have translated the more interesting and useful tracts of the text. The images are obtained from very low quality thin paper, through which the reverse page can be seen. Rather than decrease the clarity of the detail and remove the background, we have in the case of most of the images reproduced them as scanned. Wherever we reproduce the text of the published Article, it will be shown italicised within quotation marks, except with the annotations below the images which will be in blue typeface within quotation marks. We have also placed the descriptive tracts of the original text alongside the associated drawing-images, as in the original Article.

The published Article contains the .....
" ...  results of a technical investigation undertaken within its programme of work on problems of karst hydrology by the "Jovan Cvijić" Institute for Karst Research. The work was a collaborative effort with the research arm of the "Elektroprojekt" enterprise of Sarajevo, who were working in the area in connection with the utilization of hydro-energy on the River Trebišnjica. The investigations on the terrain were done in the Autumn of 1954. Participating in the research team other than myself, were Jovan [John] Petrović, Assistant to the "Jovan Cvijić" Institute for Karst Research, Bora Petrović, Engineer to the "Elektroprojekt" enterprise of Sarajevo and Borivoje Aranović, also from the "Jovan Cvijić" Institute for Karst Research."
"In addition to the importance of solving water-economy problems with the investigative work at the spring group of the River Trebišnjica, Dejanova Cave itself is undoubtedly worthy of attention from the interests of a scientific viewpoint. The mechanism of its siphons and their characteristics and their position in the circulation of underground water in karst, is also of associated interest in the solving of the hydrological problems."

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Image FP-DjP2. (above)
"Карта шире околине Дејанове Пећине. Испрекиданом линијом је означена фосилна, сува долина изнад пећине."
Map of the wider area of Dejanova Pećina. The broken lines indicate the positions or lines of the dry fossil valleys above the cave. This also indicates a line drawing sketch map of the surface area around Vrela Trebišnjice and Vrela Ćepelice, with topographic contours.
Image FP-DjP3.  Cross-sectional and longitudinal topographic profiles 
of the surface area around Vrela Trebišnjice.
Sketch maps indicating (top) the relative contours along a cross-sectional view and (bottom) the former or fossil
higher level of the surface flow of the River Trebišnjica and the present lower level, (prior to recent inundation).
."ПЕЋИНА И ЊЕНА БЛИЖА ОКОЛИНА.
["THE CAVE AND ITS ADJACENT SURROUNDINGS.]

"Dejanova Pećina is situated in the spring group area of the River Trebišnjica about 2 km. south of Bileća. The cave entrance is situated in a spacious valley formed in limestone about 1 km. wide, which is deeply incised in the surrounding terrain : From the karst springs which issue from along the edges of the base of the valley, originates the River Trebišnjica. Its strongest periodic karst spring is Dejanova Pećina."

"Dejanova Pećina is situated in the most northerly part of the limestone valley. [Ed. Miruše area.] The cave entrance faces south-east and is located at the absolute elevation of 325.2 m. asl. Above it rising like a partition is a cleft in the abrupt natural limestone cliff, rising up to a dry limestone valley above. [Ed. the so-called Bilećko Polje]. The northern part of this dry limestone valley is dissected. In here is located a dry, deep and meandering channel, very steeply descending, that only begins by the edge of the limestone valley, on the top of which a road leads from Bileća to Trebinje and Nikšić. The dry valley firstly descends towards the south then like an elbow turns toward the west to finally to repeat the turn toward the south then twisting west at its bottom end towards the present lower spring group valley, where it takes the full width of the dry valley. By reason of this meandering it cuts its way through limestone and around the dolomitic masses, as also occurs inside Dejanova Pećina, showing at one place in its relief that it cut through a hill which, at one time was 50 m. high. Thanks to its meandering, this channel has the appearance of an overturned Latin letter "S". The long north and west flanks of the aforementioned dry valley break into its larger south part section beneath whose base is located Dejanova Pećina. On the east side of the valley of the Trebišnjica Spring group area, is a low mountain mass, which itself sweeps around and away toward the east. Somewhat to the north and at the base of this mountain mass is a noticeable hollow about 10 m. and width about 25 m. This concave in the limestone appearing like a corridor, is the first part of Dejanova Pećina, formerly attracting only superficial interest."

"The long spring group area of the River Trebišnjica is formed in the limestone massif. Its western slopes rise up to Mikolj Glavni [Ed. now Nikolj Glavni] at 566 m. and then up to 700m to the watershed in the east. 
The northern edge of the area above the cave rises up to about 420 m. in elevation. In consideration of the bottom area of the location in front of and below the cave being at about 310-320 m. absolute elevation, the significance of this is that the cave is at a minimum depth of about 100 metres below the surface level."

"Up above the northern edge of this area is a spacious wide, dry valley which itself extends from the north-west to the south-east and which ends just above the area of the Trebišnjica like a hanging valley, [Ed. again, the so-called Bilećko Polje]. The mouth of this hanging valley is located about 100-120 m. above the Trebišnjica riverbed. The entirety of this dry valley is formed in the same direction as that of the present valley of the River Trebišnjica. The width of the dry valley is about 2 km. On its lowest surface can be observed shallow dolines. These undoubtedly represent the locations of old fossil springs of the River Trebišnjica. From its present appearance, it has the characteristic morphology of a typical river valley. It formerly possessed springs on two sides. On the west, one issued below Rudina and on the east, below Bobotov Duba
Together on the west and east sides are spring risings for an 8 km length along the valley. The westerly watershed of the valley can be identified as being from Gradine (944 m.), across to Iline Glave (916 m), Osoje (852 m), Tuhora (747 m) to Vodene Gradine (573 m). Moving from the east, the easterly watershed is identified as being from Kokota.(1249 m), Kovčega (1216 m), Kapora (1183 m) and Procepa (1137 m). This is very much abbreviated description of the boundary line."

"The direction of the valley and the direction of the Trebišnjica riverbed conform to the direction of that extending along the Main Canal of Dejanova Pećina."

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Image FP-DjP4.  "План Дејанове Пећине"  -  ["Plan of Dejanova Cave"].
KEY TO LEGEND :..1. Lake Water.  2. Tufa.  3. (Otseci).  4. Collapse Material.
Sketch map of the main accessible vadose passages inside Dejanova Pećina, before partial impoundment of the entrance area at the surface made the cave inaccessible and before later mid-20th century hydro-electric schemes drowned the feature completely.

KEY &  EXPLANATION of Text in Image FP-DjP4. opposite :
1. Pooled water...2. Stalagmitic Basin.
3. Abrupt vertical...4. ---- Material.

(proceeding inwards from the bridge before the entrance) :
МОСТ - Bridge.
УЛАЗ - Entrance (325.2 m.asl.)
УЛАЗНА ДВОРАНА - Entrance Chamber.
ХУМ - Hum (residual mound of bedrock).
ИСТОЧНИ КАНАЛНИ - East Canal.
СИФОН УЛАЗНЕ ДВОРАНЕ - Entrance Chamber Syphon (Sump).
 ГЛАВНИ КАНАЛ - Main Canal.
ЦЕНТРАЛНО ЈЕЗЕРО - Central Lake.
ЗАПАДНИ КАНАЛ - West Canal.
СИФОН ЗАПАДНОГ КАНАЛА - West Canal Syphon (Sump).
ЦЕНТРАЛНА ДВОРАНА - Central Chamber.
КАНАЛ СА ЈЕЗЕРОМ - Canal by the Lake.
КРУЖНА ДВОРАНА - Circular Chamber.
УЗЛАЗНИ КАНАЛ - Ascending Canal.
ГРЕБЕН - Ridge.
КРАЈЊА ДВОРАНА - Terminal Chamber.
ПАРАЛЕЛНИ КАНАЛ - Parallel Canal.
ПРЕЧАГА - Step (up to Short Cut).

СТРМ ОТСЕН СА БЛОКОВИМА - Way on made abruptly difficult by Blocks.


Image FP-DjP5.  "Уздужни профили Дејанове Пећине"  -  ["Longitudinal profiles of Dejanova Cave"].
KEY TO LEGEND :..1. Limestone.  2. Dolomite.  3. Clay.
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Image FP-DjP6.  "Попречни профили најужих делова Главног (А) и Западног (Б) Канала" -
["Transverse profiles of the narrowest parts of the "Main Canal" (A) and the "West Canal (B)".]
[The Scale is in metres.]
"МОРФОЛОГИЈА КАНАЛА ДЕЈАНОВЕ ПЕЋИНЕ.
["MORPHOLOGY OF THE PASSAGES OF DEJANOVA CAVE.]

"The entrance of Dejanova Pećina has a three-cornered appearance turning then straightening from the south-east to the south-west. The width near the bottom is about 4 m. and it is about 6.5 m. high. It has an absolute elevation at 325.2 m. asl. This form of transverse profile entrance is geologically pre-disposed.
The entrance part of the cave has the appearance of a short tunnel. On its left or west side is observed a "V" shaped "roof crevice" or vertical passage. It courses obliquely toward the west and exits above the entrance of Dejanova Pećina. The upper opening to the surface has the appearance of an ellipse of diameters 2 m. X 0.6 m. and is located 10.5 m. above the base of the main entrance of the cave. Above the upper opening again can be observed a space which entirely undermines a minor canal in a cleft and which resembles the arch of a siphon spring. Its upper wall is 3.4 metres above its base at the cave entrance. Its opening is hollowed out for 2.5 m. The total length is 7.1 m. Within its narrow middle part it has a diameter of about 1 metre. (See the right-end of the top longitudinal profile within Image FP-DjP5. opposite.)

"Immediately inside the entrance, the cave increases into a spacious chamber whose greatest parts (middle and western) contains the water of the lake. This is the "Entrance Chamber". Its length in a north-south direction is about 25 m. (82 feet) and its width is about 20 m. (66 feet). The roof rises in an arch to a visible height of 12m.-15 m. (39 - 49 feet). During the present research the level of the lake water was at an elevation of 324.5 m. asl. (05 October 1954), which in relative terms is 0.7m. below the bottom of the cave entrance and about 1.5 m. below the bottom of the riverbed which takes the streamwater from the cave after temporary periods of rainfall during the year. The base of this small streambed slopes down from the Entrance Chamber towards the small bridge in front of the cave and then is further inclined towards the streambed of the Trebišnjica. The depth of the lake water is about 1 metre but is suspected to increase in the greater part of the Chamber next to the only limestone wall.
In the wall of the middle part of the Entrance Chamber towards the west, is observed a narrow vertical opening in which is seen a fissure having a small diameter of 0.6 metre and its greater diameter being about 3 m. This is the entrance of a short eliptical recess which is 8 m. long and at its greatest width is about 2.5m. The lower part of this recess is underwater. It represents the exit to the "Entrance Chamber Syphon" from which both underground water and rainwater emerge to form the stream from the cave. This recess is formed along the same pre-dispositioned major joint, orientated in a south-east / north-west direction, as the one in the cave entrance."

"From the Entrance Chamber run three cave passages - the "West Canal", which extends west then north-west; the "Main Canal", which runs north then north-west and one small fissure-passage running east then north-east."

"The Main Canal extends mainly in a north-west direction with its base undercut to the east. It is spacious and from its beginning in the Entrance Chamber, is from between 3.5 m. to 4 m. wide and is 5 m. high. Its steeply sloping side walls are inclined down to the east and its cross-sectional profile is eliptical in shape. At a point 14 m. in from the beginning of the passage, on its west side at its base, can be observed a horizontal opening to a fissure. This is the opening to one short recess and a drop which is 1.7 m. deep. This superficial passage is a way through to the "Central Lake" whose level is identical to the water level of the lake in the Entrance Chamber. Coming from the Main Canal one can see through to the Central Lake over a limestone ridge of 2 m. high and 3 m. wide. Exiting over this step on to a low platform from the Main Canal, you arrive at the rounded shore of Central Lake at its most southerly part. East of this platform is observed a short cave passage which continues below water-level.

[To be continued]

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Image FP-DjP7.  "Шематска скица механизма рада пећинских сифона Дејанове Пећине" -
["Schematic sketches of the mechanism of the working of the cave syphons of Dejanova Cave"].
"ХИДРОЛОШКЕ ПРИЛИКЕ И МЕХАНИЗАМ РАДА ПЕЋИНСКИХ СИФОНА.
["HYDROLOGICAL CIRCUMSTANCES AND THE WORKING MECHANISM OF THE CAVE SYPHONS.]

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DESCRIPTIVE SUMMARY :
"Dejan's Cave" is formed in Upper Cretaceous Limestone and Dolomites. In terms of karst hydrology, it is predominantly an Allogenic (B-Type) Karst Resurgence Spring, with significant Authigenic (A-Type) contributions. As such, we would expect a considerable build-up of sediment to have accumulated in the form of a sediment-fan at the base of the reservoir downstream of the spring-zone.
The complexity of this very dynamic karst spring zone is illustrated by the simplified plan and sections of the previously accessible cave passages, which were surveyed at a time of low water. The surveyed cave passages total 510 metres (1673 ft.) in length, all of which is now submerged deep below the impounded water of the HET Company's Bileća Lake Reservoir. The karst hydrological mechanism of the outlet zone as interpreted by Petrović.in his simplified sections given in.Image FP-DjP7..above, indicate that the main entrance at Dejanova Pećina is an intermittent spring under natural conditions. The interconnected spring outlets downstream of Dejanova Pećina at Vrelo "Oko" and Vrelo "Nikšičko" continue flowing long after the yield at the main outlet has reduced or has even stopped.

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FUTURE EXPLORATION :
As for the possibilities of a modern technical investigation of this complex karst spring-cave zone, such an enterprise would be encumbered by the present depth of submersion of the whole cave system beneath the HET Company's Bileća Lake, impounded by its Grančarevo Hydro-electric Dam. At the maximum level of water impoundment [ie..400.09 m.asl. (1313 feet a.s.l.)], the cave entrance would be situated 75 metres (246 feet) below the level of the artificial lake. A modern exploration of the cave is technically possible but has an inherently high level of risk attached to it. One aspect of minimizing the many risks would be to co-ordinate the underwater exploration at a time of very low water in the lake combined with very low underground water flows. Such a time would be in the late summer period following a dry winter or even better, following a long series of dry winters. Such rare and ideal circumstances ocurred in the summer of 2003 but the opportunity of diving was not taken up at that time.
At the present stage of planning, a reconnaissance dive was due to take place in the Summer of 2005., in order to ascertain the accessibility of the main cave entrance and its condition together with the nature of the physical problems encountered. The water conditions were far from ideal and the dive was postponed.
If it is deemed to be useful and sufficient information arises from such a reconnaissance dive in the future, a separate Webpage will be annexed via a Link within the Fatničko Polje Webpages - Section 2., to provide both the dive results and any associated future plans.

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