Habic, Peter

Revistes Catalanes amb Accés Obert

ENDINS, n.' 13.1987. Ciutat de Mallorca. 
USE AND REGULATION OF KARST POLJES 
IN YUGOSLAVIA 
by Peter H A B I ~  * 
Abstract 
The traditional use of karst poljes in different parts of Dinaric karst is presented frorn the efforts 
for water regirne change in order to dry up the poljes as well as to retain periodically or perrnanent- 
ly the water for agricultural, touristical, energetical and cornplex hydro-econorny use. The atternpts 
for protection of karst poljes natural properties within the frarne of regional karst park are rnen- 
tioned. 
Extrait 
On y présente I'emploie traditionelle des poljés karstiques dans les différentes parties du karst 
Dinarique et tous les efforts de changer le régime hydrique, ainsi dans la direction du desséchernent 
cornme dans celle de la retenue permanente ou périodique de I'eau pour I'exploitation agriculture- 
Ile, touristique, énérgetique et pour I'econornie hydraulique complete. On y rnentionne les efforts 
pour la protection permanente des caractéristiques naturelles des poljés karstiques dans le cadre du 
parc karstique régional. 
Big karst depressions with flat, alluvial bottom 
and sinking streams which are in the geographical 
literature the most frequently defined as karst pol- 
jes (~v i j i c ,  1895; ~erko ,  1947; Melik, 1959; ~ogl ic ,  
1964; Gams, 1978), according to ~ e r k o  there are 
more than 200 of them in Yugoslavia, are the only 
bigger, fertile and inhabited oases in the middle of 
the Dinaric karst. Man exploits them from the be- 
ginning of settling by different ways, adapts to 
their natural properties, more or less successful he 
tries to change them according to his own wishes 
and needs. In the last decades in Yugoslavia quite 
a big progress was attained. 
1. Traditional use of 
karst poljes 
According to morphogenetical and hydrogra- 
phical criteria the karstologists divided karst poljes 
into severa1 types (Lehmann, 1959; Gams, 1973). 
Regarding their economic geographical properties, 
* lnstitut za raziskovanje krasa ZRC SAZU. 
YU-66230 POSTOJNA, Titov trg 2. 
it means the situation, size, water conditions and 
climate and regarding the manner of economic use 
the dinaric kast poljes can be divided into fol1,owing 
groups: 
1.1. Permanently flooded lake poljes on low 
above the sea leve1 altitudes without an im- 
portant agricultural surface and urban func- 
tion, convenient for natural reserve, tourist 
exploitation and natural reservoir of water; 
such are Vrana on island Cres, Vransko jezero 
near ~ ibenik,  BaEinska jezera near Neretva, 
Skadarsko jezero, etc. 
1.2. Submediterranean, periodically, partly or 
completely flooded karst poljes with fertile 
agricultural surface, which can be intensively 
cultivated in the dry half of the year when the 
water flows off. Their use depends on size 
and lasting of flood. Mediterranean climate 
with favourable temperatures accelerates the 
agrarian production, but summer aridity di- 
minishes it. Permanent settiements and com- 
munication system are situated on the border 
of the flooded surface, agricultural land lies 
in the flood area too. Such poljes are: 
Imotsko, Popovo, Rastok, Jezero, etc. 
1.3. Dry karst poljes in submediterranean belt are 
regarding the size smaller but more fertile; 
the lack of water diminishes their economic 
value (Dugo polje, Dicmo, Ljubinje). 
1 4. Temporary flooded poljes in the mountainous 
continental part of Dinaric karst are regarding 
the climatic and productive conditions more 
suitable for cattle-breeding, either exclusively 
as grassland and pasture ground or supple- 
mentary agricultural surfaces for mainly cattle- 
breeding onented farms. The way of economic 
use is in great extent influenced by lasting 
and annual variability of floods, but the agri- 
culture is limited too by the altitude and 
lower temperatures connected to climatic in- 
version. Beside cattle-breeding on the poljes 
the woods are important on the poljes bor- 
ders encouraging the woodworking industry. 
1.5. Dry karst poljes in higher continental part of 
Dinaric karst in between the wood belt are 
suitable exclusively for grassland and cattle- 
breeding (GlamoEko polje, Babno polje). The 
wood on littoral mediterranean side is extre- 
mely degraded or even completely extinguish- 
ed because of exaggerated exploitation, as for 
example in Montenegro (Cetinje, Grahovo, 
NjeguSi). 
Beside the agricultural function the poljes are 
important because of their situation among higher 
karst ridges for their communication significance. 
Across them the old roads had been leading from 
the interior towards the coast and back, modern 
circulation communications, more roads than rail- 
way, are there too. At cross-roa+ on poljes sma- 
ller urban centres developed, being the industry 
centres and causing new problems regarding pro- 
tection and management of karst. 
On some poljes of tectonic origin with Neo- 
gene lacustrine sediments there are stocks of 
brown coa1 and lignite which are more and more 
important as energetic sources (Gacko polje). Su- 
perficial waters on dinaric poljes with common un- 
derground connections and possibilities for cons- 
truction of greater accumulations on the different 
altitudes present the main energetic potential of 
Dinaric karst (TrebiSnjica system, Cetina). 
2. The purpose of intervention 
into the karst water regime 
By social economic development and building 
industry progress as well as by research results the 
human intewentions on karst poljes increased, 
specially regarding their water regime by drying 
them up, partly by irrigation and mostly by exploi- 
tation of available energetic potential. According to 
exploitation the interventions into karst poljes can 
be divided to: 
2.1. Arrangement of water conditions for the need 
of agriculture and cattle-breeding production 
by either drying up or irrigation with local 
use of water energy at springs and ponors. 
2.2. Arrangement exclusively for energetic use by 
construction of accumulation basins and arti- 
ficial outflow tunnels and energetic plants. 
2.3. Arrangement for several purposes of water 
economy use, agricultural, energetic and tou- 
ristical ones and by limited coordination of 
ecological and landscape problems. 
2.4. Preservation.and consewation of natural un- 
changed properties in a form of reserves, 
touristic curiosities or protected catchment 
areas of water sources. 
3. Problems of karst poljes 
reg ulations 
Forms, ways and problems of regulation and 
use of karst poljes are connected with: 
3.1. knowledge degree of karst phenomena and 
karst processes investigation rate on the sur- 
face and in the underground of narrow and 
wider background, 
3.2. technical mastery degree of karst pheno- 
mena and their progress and ecological law- 
fulness, 
3.3. the expanse of interventions, 
3.4. accordance and coordination of interventions 
to purpose, 
3.5. expected and secondary effects, 
3.6. cost of intewentions and other fees, 
3.7. valorization of natural properties in present 
and in future, not yet known, economic and 
social demands. 
According to tasks and needs the research 
methods and technical interventions as well as the 
organisational management demands have been 
considerably ameliorated (Herak, 1972; Mikulec & 
~ rumic ,  1976; Milanovic, 1978). 
4. lmproved research methods 
On the research area the efforts were directed 
to: 
4.1. lnventarisation and classification and carto- 
graphic documentation of the karst pheno- 
mena in the poljes region as well as in their 
wider background. From this point of view 
were important geological, geographical 
speleological investigations beside the 
detic surveys. 
4.2. Finding of water quantities, regime, precipita- 
tion budget, inflow and outflow - for al1 these 
tasks the improved hydrometeorological ser- 
vice has taken care. 
4.3. Finding of underground water connections 
on outflow side by corresponding springs 
and definition of catchment area on inflow 
side. The water tracing methods were intro- 
duced and improved (different tracers were 
used), somewhere in big quantities. Water 
tracing methods were improved by interna- 
tional collaboration of different institutions 
(1st - 5 th SUWT). 
4.4. Study of cavernosity and permeability and 
distribution of different hydrogeological . 
units, complete, partial and hanging barriers, 
influencing to distribution and direction of 
karst underground waters flow. From this 
point of view the geological investigations by 
detailed mapping and boring, geomechanical 
and geophysical measurements and analyses 
contributed the most. 
4.5. At first bigger technical interventions the 
planners had not taken enough care for natu- 
ral and ecological investigations. They follow- 
ed later, when the problems of preservation 
of endemic subterranean animal specimens 
have emerged, when the changed microcli- 
matic conditions and troubles of human 
adaptation to new conditions in life, empty 
settlements, interrupted roads, disturbed 
agrarian production and agricultural use and 
other different results and changes in karst 
ecosystem have occurred. 
5. Ways and effects of 
technical interventions 
While planning and realizing the regulation 
projects some new methods have been introduced 
just because of specific karst circumstances. 
5.1. By previous cleaning and opening of ponors 
no essential ameliorations of poljes water re- 
gime have been achieved; on one side a man 
wanted to avoid the floods while on the other 
he surpasses the lack of water in dry summer 
months by difficulties (wells, rain-water, re- 
servoirs). The majority of outflow tunnels, 
constructed on lower lying karst poljes (Je- 
zero, BokanjaEko blato, lmotsko polje, etc.) 
were not conceived on the real water condi- 
tions, the planners did not consider enough 
the entire underground water system. Thus 
the drought was increased but the floods were 
not eliminated (Bonacci, 1985). 
5.2. The attempts of simple water retention on 
poljes by closing up the swallow holes and 
by controlled water outflow into existent na- 
tural conduits did not give the expected re- 
sults either. The floods increased, threatened 
the agricultural surface and settlements on 
the border, the drying up started a little later 
but has finished more quickly (CerkniSko je- 
zero, HabiE, 1974). 
5.3. First serious attempts for permanent reten- 
tion of water on the karst poljes have been 
furthermore conceived on superficial tightning 
and isolation of the known swallow-holes. In 
the alluvium inside the artificial accumula- 
tions have occurred new one ( ~ i k ~ i c ) .  
5.4. The ill success forced the technicians to con- 
ceive new methods for deep tightning of wa- 
ter courses in karst. Practica1 realizations of 
deep injections in borders and under the su- 
perficial dams have been sometimes accom- 
panied by surprises when big caverns have 
been hit by boreholes (Lika, BuSko blato) but 
these problems have been promptly success- 
fully solved. Supplementary investigations 
and tightnings have namely ricen the costs of 
the objects, but with rare exceptions, the fo- 
reseen effects have been achieved (Mikulec & 
~ rumic ,  1976). 
6. The meaning of karst 
landscape regulation 
In the sphere of management and complex 
landscape arranging an important progress has 
been achieved. Exclusively energetic use of karst 
waters for which the only feitile and for life suita- 
ble surfaces in the middle of the karst have been 
sacrified, soon proved to be too much biassed (Mi- 
kulec & ~ rumic ,  1976). Agressive drainage of water 
through the shortest artificial way from the moun- 
tains to the sea, in spite of useful energetic objects, 
unabled the exploitation of precious karst waters 
for other purposes, water supply, irrigation, ecolo- 
gical balance, sport and tourist activities etc. The 
plans for several purposes use of karst waters and 
for available agricultural surfaces have been done, 
which had diminished the energetic profit in behalf 
of other users of water and space. On the other 
hand such way had increased the costs of building 
and indirectly the pcice of energy. Regarding the 
fees only big, connected systems are acceptable 
(for example TrebiSnjica). At particular smaller pol- 
jes the costs of intervention were too high and the 
effects too small. It is important specially when 
considering unfavourable ecological consequences 
of unilateral and exaggerated intervention into na- 
tural karst system. More reasonable natural con- 
servation and preservation rneasures were proved, 
accelerating accordant agricultural, touristical, ur- 
ban and other economic uses of karst poljes. Clas- 
sical karst poljes of Notranjsko, as are Cerknica and 
Planina poljes should be, together with their envi- 
ronrnent and several caves, arnong thern the world 
farnous Postojnska jarna, included into natural 
karst park. 
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Use and reglation of karst poljes in Yugoslavia

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