..........FP Section 2.0. Webpage Contents :
..........Paragraph 2.2....Karst Springs, Estavelles and Ponors in Fatničko Polje :
..........Paragraph 2.3....Karst Water Outlet Springs for Fatničko Polje - The Local Base levels of Erosion :
..........Paragraph 2.3.1....General Introduction and Introduction to the Zaravan Miruše :
..........Paragraph 2.3.2....Overview of the Fatničko Polje Karst Outlet Springs  :
..........Paragraph 2.3.3....The Trebišnjica River Spring-group below Bileća  /  Vrela Rijeke Trebišnjice :
..........Paragraph 2.3.4....The Čepelica Stream Spring-group  /  Vrela Rijeke Čepelice :
..........Paragraph 2.3.5....Post-1967 -  Monitored Effects during and after the Submersion of the Trebišnjica  /  Čepelica Spring-groups beneath the artificial Bilećko Jezero :
..........Paragraph.2.4....Karst Water Quality in Fatničko Polje :
..........Paragraph 2.4.1....Introduction :
..........Paragraph 2.4.2....Overview of the Chemical, Physical and Biological Parameters and Analytical Procedures.

..........Click on the underlined Links above to move down to the Sections more quickly.

KEY to Image FP2.1. above :

..........A.  Position of Underground Watershed  /  Usvojena vododijelnica radi proračuna sliva  /  Усвојeна вододијелница ради прорачуна слива.
..........B.  Watershed Zone  /  Vododijelnička zona  /  Вододијелничка зона.
..........b - b'  Variable Boundaries of the Underground Watershed Zone  /  Granice vododijelničke zone (takođe su podložne promjeni)  /  Границе вододијелничке зоне (такођe су подложне промјени).

..........Introduction of the spores  /  Upotredljene spore  /  Упotредљене спoрe.
..........Z.  Green  /  zelene  /  зелене.
..........C.  Red  /  crvene  /  црвене.
..........P.  Blue  /  plave  /  плаве.
..........N.  Un-coloured  /  neobojene  /  неoбoјене.
..........V.  Violet  /  ljubičaste  /  љубичасtе.

2.3.    KARST WATER OUTLET SPRINGS FOR FATNIČKO POLJE - The Local Base levels of Erosion :
2.3.1.    General Introduction and Introduction to the Zaravan Miruše :
As indicated in Image FP2.1. above, a bifurcated hydrology exists beneath the floor of Fatničko Polje, giving the phenomenon of two Local Base Levels of Erosion. Under certain high water conditions, a relatively small proportion of the water leaving the polje travels north-west to resurge at the Bregava Karst Springs (Vrela "Bregava"). This particular aspect will be dealt with in future webpages dedicated to Dabarsko Polje.

The majority (85-90%) of water leaving Fatničko Polje (or permanently flowing through the phreatic karst conduits beneath the polje), travels south-east to resurge at karst springs in the now-submerged floor of what is now the HET Bileća Lake (Bilećko Jezero), in an area which was formerly known as the "Zaravan Miruše" or Miruša Plateau. Prior to submersion, this was one of the two former LOCAL BASE LEVELS OF EROSION for Fatničko Polje. This artificial lake has also been known as the Akumulacija Bazena Miruša. Its lower reaches encroach into Montenegrin Herzegovina.
This very interesting area in its own right, has a complex karst hydrological functionality and is situated at an average altitude of 330m. asl. (1083 ft. asl.) and is orientated north north-west / south south-east. As a single karst geomorphological feature and prior to submersion, it may be considered as being an open karst polje; that is, open at its downstream or outlet end only. Its downstream outlet area begins at the north side of the dolomitic "hydrological barrier" near Dobričevo, taking the form of a karstic canyon about 7 km. long. The karstic canyon continues downstream in a southerly direction, past the Estavela "Kljen" at Dobričevo and the Ponors at Tmuša and the Ponors at Pares and the Ponor "Mlinica", opening out again into Trebinjsko Polje at the Grančarevo dolomitic "hydrological barrier" 700m. downstream of the Vrelo "Oko" spring group at Pares.

As an important aspect directly connected with the hydrological functionality of Fatničko Polje, the two northern extremities of the "Zaravan Miruše" are dealt with here in great detail, addressing both the historical and present situations.

2.3.2.    Overview of the Fatničko Polje Karst Outlet Springs  :
The Fatničko Polje Karst Outlet Springs comprise two geographically and hydrologically-distinct principal groupings. These are :-

..........a)  The Trebišnjica River Spring-group below Bileća / Izvorište Trebišnjice located at 325 m.asl. (1066 ft);
..........b)  The Čepelica Stream Spring-group / Izvorište Čepelice located at 324 m.asl. (1063 ft).

These separate spring-groups are often and rather confusingly referred to in the literature as the "Trebišnjica Springs", with data presented as if it were a single source. Although they are obviously connected at a point somewhere within the underground conduit aquifer, there are significant differences in their hydrological and hydrometric characteristics such that they must be considered as separate hydrologic entities.
An example of published data which combines the hydrological characteristics of the sources, is as follows :-

.........."TREBIŠNJICA" SPRINGS /  VRELA "TREBIŠNJICA" :
..........Q_min    =  2 m³  sec ^-1
..........Q_mean  =  80 m³  sec  ^-1
..........Q_{max normal}    =  > 300 m³ sec ^-1
..........Q_{max extreme}   =  864 m³ sec ^-1
..........Catchment area  =  1144 km²
..........Straight-line distance to furthest ponor in Gatačko Polje  =  34 km.
..........Difference in Vertical elevation to furthest ponor in Gatačko Polje  =  520 m.
..........Difference in Vertical elevation to furthest ponor in Cerničko Polje  =  480 m.
..........Difference in Vertical elevation to the floor of Fatničko Polje  =  130 m.
..........Underground flow-time from ponors in Gatačko Polje (at minimum "water table")  =  35 days.
..........Underground flow-time from ponors in Gatačko Polje (at maximum "water table")  =  5 days.

In the paragraphs below, we offer some hydrological and other data regarding each individual spring-group. Further information will be added when it becomes available. We have located some historical monochrome and colour images of the areas of interest. These are now included here.

2.3.3.    The Trebišnjica River Spring-group below Bileća  /  Vrela Rijeke Trebišnjice :
This Karst Spring-group has one of the largest yields of water of any spring in Europe and is the direct, permanently flowing source of the Karst River Trebišnjica, formerly the largest disappearing karst river in the world. The following archive photographs indicate details of the area in very different periods of time. We have ensured that the images are of sufficient quality for positional-comparison of the essential features. Each of the photo-archive views has been photographed from a different viewpoint. We thank both Mr Bogdan Prelević for acquiring the photo-archives below and Dr Dragan D. Tabaković for his detailed input to the description of various features in the archive photographs.
However, we start with two Military Maps from the period of late Austro-Hungarian Administration (1912) of Bosnia & Herzegovina, showing topographic details of the Bileća area. Note that the "Trebišnjica Springs" [Vrela Trebišnjica] are annotated as the "Trebinjčica Quellen".

Originally, 3.25 km downstream of the spring-source was the confluence with the smaller Karst Stream Čepelica, which thereafter, periodically adds considerably to the surface flow of the Trebišnjica. The local topographical name for the point of confluence of the Rivers Trebišnjica and Čepelica is "MISTIALj".
The Trebišnjica River Spring-group consists of the main karst hydrological features :

..........a)  "BILEĆKA VRELA"  :
..........-  This is reported to have some 7 separate spring-cave outlets.
..........-  The main opening, Dejanova Pećina, appears as a cave entrance 4 m (13 feet) wide and 6.5 m (21.5 feet) high.
..........-  Another opening is Vrelo "Oko", which is a lower outlet of Dejanova Pećina System, is the permanently flowing outlet which continues to issue water even when the Dejanova Pećina outlet stops flowing. It is located about 200 metres downstream of Dejanova Pećina, on the left bank of the Trebišnjica River;
..........-  Another opening is Vrelo "Nikšičko";
..........-  Another opening is Kostova Pećina beside the main resurgence pool of Dejanova Pećina and possessing its own short canalized outflow streamway;
..........-  All outlets have with a direct ephemeral connection to the Ponor "Pasmica" in Fatničko Polje, a straight-line surface distance of 17.2 km. and a direct permanent connection with the ponors in Cernčko Polje.
..........-  All outlets are centred around a junction of a geological overthrust fault with another fault in Upper Cretaceous Limestones and Dolomites.

..........Established Underground Flowline Data with the Ponor "Pasmica" in Fatničko Polje :

a)..Date of Test  =  01 January 1955. Method  =  Na-fluorescein. "Pasmica" Ponor Condition in Fatničko Polje  =  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. "Pasmica" Ponor Condition in Fatničko Polje  =  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. "Pasmica" Ponor Condition in Fatničko Polje  = 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. "Pasmica" Ponor Condition in Fatničko Polje  =  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.

..........c)  VRELA "LERSKO OKO" / VRELO i PEĆINA "OKO" :
..........This karst spring group has some 5 outlets and is located 5 km south of Vrela Trebišnjice. It consists of the permanently flowing spring, the periodic spring and 3 others. This was thoroughly investigated and mapped to a scale of 1 : 100 by the NR-BiH Speleological Society before the reservoir downed its entrance.
In their retrospective Report of 1979 by Gašparović, (Naš Krš Journal, V., (7).), the Speleološko društvo "Bosansko-Hercegovački krš" reports that;

"[in 1961] At the request of the Director of the HET Co., Trebinje, the Speleological Society of Bosnia and Herzegovina of Sarajevo, organized the detailed speleological research of the karst springs and caves of "Oko" and others across the breadth of the surrounding area and for a distance of 5km south from the Trebišnjica Springs. This research required the obtaining of the detailed morpho-hydrographic situation with due consideration that this part was required to be submerged by water from the Grančarevo Accumulation.
The karst spring and cave "Oko" was surveyed and mapped to a scale of 1 : 100. By means of a ground-plan figure of the spring canal system, we could show where water would flow out to the surface. Establishing the flow direction of the water was accomplished with depth-sounding instruments and by hydrometric measuring."

The Čepelica Spring-group consists of the main karst hydrological features;

..........a)  VRELO "ČEPO" :
..........-  It has 3 outlets located at a geological overthrust fault and all of which have a direct connection to the Ponor "Pasmica" in Fatničko Polje, a straight-line surface distance of 17.2 km. This cave entrance is of a large diameter.

..........Established Underground Flowline Data with the Ponor "Pasmica" in Fatničko Polje :

 

a)..Date of Test  =  27 November 1958. Method  =  Na-fluorescein. "Pasmica" Ponor Condition in Fatničko Polje  =  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  = 1959. Method  = Na-fluorescein. "Pasmica" Ponor Condition in Fatničko Polje  =  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.

2.3.5.    Post-1967 -  Monitored Effects during and after the Submersion of the Trebišnjica  /  Čepelica Spring-groups beneath the Artificial Bilećko Jezero :
The HET Co. Bileća Lake (Bilećko Jezero) is an artificial reservoir. The initial filling of the reservoir was begun on 21 August 1967 after the completion of the construction of the 123 m. (403.5 feet) high hydro-electric Grančarevo Dam. The impounded water has an effective elevation H_max of 400.09 m.asl. (1313 feet), creating a maximum surface area of 27.6 km² and containing a maximum impounded volume of 1.3 billion m^3..of water. Milanović states that there is evidence that this impoundment creates an additional underground storage volume, estimated to be about 15% the volume of the surface reservoir, ie. 1.3 x 10⁹ m³ water, contained in the caverns, fissures and conduit aquifers of the karstified limestone between Bileća and Fatničko Polje.
During the formation of the artificial lake and the drowning of the two karst spring-groups, hydrological observations via borehole piezometers in the area behind the Trebišnjica River Spring-group below Bileća indicated the existence of an underground accumulation of water, whose volume was estimated to be about 15% of the volume of the surface accumulation.
The flooding of the Miruše area has had several permanent effects on the hydrological functionality of Fatničko Polje :-
..........-  When the level of the Bilećko Jezero is below 360 m.asl. (1181 feet), the natural karst hydrological régime operates.
..........-  When the level of the Bilećko Jezero is between 360-370 m.asl. (1181-1214 feet), the influence of the Lake is observed only in the hydrology of the immediate background area of the Trebišnjica River Spring-group below Bileća.
..........-..When the level of the Bilećko Jezero is above 370 m.asl. (1214 feet), it affects the hydrology of the more distant background as far away as Fatničko Polje and Plana. The observed effect is that the rate of the rise of maximum flooding levels in Fatničko Polje is altered, because the difference in elevation between the

Ponor "Pasmica", the principal outlet for the water in Fatničko Polje, and the Trebišnjica River Spring-group below Bileća decreases from 130 m. (427 feet) to 64 m. (210 feet).
..........-  When the level of the Bilećko Jezero is at 400 m.asl. (1312 feet), and the inflow to the Lake is  >125 m³ sec ^-1  the level is maintained.
..........-  The critical inflow at the Bilećko Jezero level of 397 m.asl. (1302 feet) needed to overflow it is 220 m³ sec ^-1.
..........-  A new karst-water outflow point has formed at a level of 363 m.asl. (1191 feet) in the vicinity of the Dejanova Pećina, due to the unblocking of old and previously inactive underground karst canals.
..........-  The effective elevation H_max of 400.00 m.asl. (1312 feet) of the Bilećko Jezero is at the same elevation as the level beneath Fatničko Polje at which the bifurcation of its hydrology is initiated and water loss begins to take place in the direction of the Bregava Springs.
(We should perhaps be grateful that at least this self limitation has been designed into the hydro-electric infrastructure!)
Some of this data is used by the HET Company in controlling the balance between maintaining the throughflow of water whilst generating electricity.

In general and on average, it has been reported that the creation of the Bilećko Jezero has reduced the height of the flooding in Fatničko Polje by 1.8 metres, although it has increased the length of time of the flooding events.
At maximum water-level (when this is coincident with heavy atmospheric precipitation), the Bilećko Jezero has also created new karst spring sources in the area known as "Bilećko Polje". This is the shallow basin area to the north of the town centre of Bileća, at a mean elevation of 430 m.asl (1476 feet).
By definition of the term, it is not a true "karst polje", even though it is often referred to as such in the literature. The Bileća area is not dealt with here in the Fatničko Polje webpages.

In connection with our investigative research currently being undertaken in Estavela "Obod" in Fatničko Polje, it has become apparent that the low-water levels prevalent in the dry season in the early 1960's before the drowning or submersion of the Local Base Level of Erosion outlet springs, can no longer be observed.
This is borne out by comparing the 1960's cave survey of the accessible vadose cave passage at the bottom of the Estavela "Obod" 1st Underground Vertical, with what can be observed now at low-water level. This short section of previously accessible Vadose Master Cave is also now permanently under water.
(Please refer to the details given in Section 8. of the Fatničko Polje webpages.)

The actual prevailing water-level of the Bilećko Jezero can be obtained from the water-measuring station at the Grančarevo Facility or from the HET Company Offices in Trebinje.

The water quality at all locations in the polje will vary greatly with time and as a result of the prevailing human-impact and of short and long-term changes and fluctuations in the natural environment.
The Fatničko Polje Karst Water Quality Database and Species Sightings Records will be the receptacle for our recorded observations only in this polje and is undertaken within the remit of the separate Principal sub-Project No. 2. ["Speleological Investigation of Fatničko Polje"] of the Main BiH Project :-

(NB. It should be noted that, as a permanent feature, a separate Database will be the receptacle for our recorded observations in all other geographical areas of the Main BiH Project No. 3.)

2.4.2.    Overview of the Chemical, Physical and Biological Parameters and Analytical Procedures :
The paragraphs below give an insight into the karst water sampling philosophy and our general approach to physico-chemical, chemical, biological and micro-biological analysis to yield the most accurate, reliable and repeatable results. We have removed the previously incomplete details referring to actual chemical analytical procedures, which are now in a completed and greatly expanded form. Although this information has been relocated into the Technical Support Pages for Project workers in the pages of the Main Project, it is also available as MS Word v.7. documents in A4 format, via Links with unrestricted access located near the bottom of this Page.
..........2.4.2.1....General Principle of Karst Water Sampling Procedures and Notes :
..........-  Insofar as aqueous carbonate / hydrogen carbonate chemistry is inherently unstable, all physico-chemical parameters relating to this chemistry are determined in situ at the sampling site, whether underground or not, and are most definitely not sampled and transferred in containers to a laboratory site for chemical analysis at a later time.
..........-  Insofar as cleaning the electronic instrument electrodes are concerned, these should only be rinsed in de-ionized water. Distilled water is not a suitable alternative.

In situ or dynamic analysis is therefore undertaken for the following determinants :-
..........pH,  E_h,  Dissolved O₂,  Total Hardness, Calcium Hardness, Magnesium Hardness, Hardness Saturation Level (with respect to calcium carbonate), sample Temperature,  ambient Temperature,  Electrical Conductivity,  and Total Dissolved Solids.
The results arising from such analyses are referred to as the dynamic pH and the dynamic E_h  etc., as opposed to results taken from static samples which have been collected, taken away from the site and analysed at a later time.

..........2.4.2.2....The Physico-chemical Determinants and Analytical Procedures :
The following is a list of the determinants which we have begun monitoring in 2002 and the hydrological years beyond, in what was an interim approach both to the short-term plan of karst water analysis in the polje and to the long-term plan for similar monitoring of all Proteus anguinus Habitat Locations in the Trebišnjica Karst River Catchments. This flexible type of approach has already allowed us to develop and establish a suitable and relevant permanent monitoring régime, enabling us to begin developing a Data Series for all Proteus anguinus Habitat Locations for at least the 30 year period of the life of the Project.
.
...........  dynamic pH  /  dinamic pH  (0.00 -14.00)
.............direct method using a Palintest PT146 Electronic Waterproof 800 Microcomputer with Glass Electrode and Temperature Probe and with Temperature Compensating Device set at automatic for 25 º C.
...........  dynamic Electrical Conductivity  /  dinamic Električna Provodljivost  (µS / cm.) direct method using a Palintest PT146 Electronic Waterproof 800 Microcomputer with Conductivity Probe and Temperature Probe.
...........  dynamic Total Dissolved Solids  /  dinamic Količina rastvorene materije  (mg / litre)  direct method using a Palintest PT146 Electronic Waterproof 800 Microcomputer with TDS Probe and Temperature Probe.
...........  dynamic Eh Redox Potential  /   (mV)  direct method using a Palintest PT146 Electronic Waterproof 800 Microcomputer with Eh Probe and Temperature Probe.
...........  sample Temperature /  Temperatura vode  ( º Celsius)  direct method using a Palintest PT146 Electronic Waterproof 800 Microcomputer with Temperature Probe.
...........  ambient Temperature  /  Temperatura vazduha  ( º Celsius)  direct method using a Palintest PT146 Electronic Waterproof 800 Microcomputer with Temperature Probe.
...........  dynamic Dissolved Oxygen  /  Kiseonik  (mg / litre)  direct method using a Palintest PT148 Dissolved Oxygen Meter and Temperature Probe.  (not yet undertaken)
...........  dynamic Turbidity  /   (NTU)  direct method using Palintest Micro 900 Turbidimeter.  (not yet undertaken)
.
...........  dynamic Calcium Hardness  /  dinamic Kalcijum Tvrdoca  (as mg / litre calcium carbonate) direct method by EDTA Titrimetric Complexometry.
...........  dynamic Magnesium Hardness  /  dinamic Magnezijum Tvrdoca  (as mg / litre calcium carbonate)  direct method by EDTA Titrimetric Complexometry or through calculation "by difference".
...........  dynamic Total Hardness  /  dinamic Ukupna Tvrdoca (as mg / litre calcium carbonate) direct method by EDTA Titrimetric Complexometry.
...........  dynamic Carbonate Under-  or Super-Saturation Level  / dinamic Zasićenost  (as mg / litre calcium carbonate)  direct method by EDTA Titrimetric Complexometry.
.
........... .total Copper  /  Ukupna Bakar  (mg / litre Cu)  direct method by Palintest tablet count.
...........  Chlorides  /  Hloridi  (mg / litre Chloride)  direct method by Palintest tablet count.
...........  Nitrates  /  Nitrati  (mg / litre Nitrate)  direct method by Palintest tablet count.
...........  Phosphates  /  Fosfati  (mg / litre Phosphate)  direct method by Palintest tablet count.
...........  Sulphates  /  Sulfati  (mg / litre Sulphate)  direct method by Palintest tablet count.
...........  Ammonia  /  Ammonijak  (mg / litre Ammonia)  direct method by Nutrafin reagent drop count test.
...........  Iron  /  Gvožde  (mg / litre Iron)  direct method by Nutrafin reagent drop count test.

Additional qualitative values will be added to the list above as of August 2009.

..........2.4.2.3....EDTA Complexometric Titrimetric Determination of Calcium, Magnesium and Total Hardness and the Determination of the Carbonate-saturation value :
There are standard procedures for determining the above parameters and which can be reliably employed underground by appropriately trained personnel for in situ analysis. The analytical procedures detailed below have been reliably used in the Devon Karst Research Society's "UK Karst Hydrological Programme" since 1976.

The sampling procedures and chemical analytical methodologies were agreed upon and the relevant training of the Project's Research Assistants was completed during 2003. Revision training is undertaken annually during at least one of the Society's visits. All materials resourcing has been achieved.
The initial, interim methodologies using Palintest Tablet Count procedures are now reserved for non-carbonate determinations and it is to be hoped that they will be replaced in due course with more accurate methods.