ENDINS, n.' 13.1987. Ciutat de Mallorca. |
USE AND REGULATION OF KARST POLJES
by Peter H A B I ~
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-
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
it means the situation, size, water conditions and
and sinking streams which are in the geographical
climate and regarding the manner of economic use
literature the most frequently defined as karst pol-
the dinaric kast poljes can be divided into fol1,owing
jes ( ~ v i j i c ,
1895; ~ e r k o ,
1947; Melik, 1959; ~ o g l i c ,
1964; Gams, 1978), according to ~ e r k o
1.1. Permanently flooded lake poljes on low
more than 200 of them in Yugoslavia, are the only
above the sea leve1 altitudes without an im-
bigger, fertile and inhabited oases in the middle of
portant agricultural surface and urban func-
the Dinaric karst. Man exploits them from the be-
tion, convenient for natural reserve, tourist
ginning of settling by different ways, adapts to
exploitation and natural reservoir of water;
their natural properties, more or less successful he
such are Vrana on island Cres, Vransko jezero
tries t o change them according to his own wishes
near ~ i b e n i k ,
BaEinska jezera near Neretva,
and needs. In the last decades in Yugoslavia quite
Skadarsko jezero, etc.
a big progress was attained.
1.2. Submediterranean, periodically, partly or
completely flooded karst poljes with fertile
agricultural surface, which can be intensively
1. Traditional use of
cultivated in the dry half of the year when the
water flows off. Their use depends on size
and lasting of flood. Mediterranean climate
According to morphogenetical and hydrogra-
with favourable temperatures accelerates the
phical criteria the karstologists divided karst poljes
agrarian production, but summer aridity di-
into severa1 types (Lehmann, 1959; Gams, 1973).
minishes it. Permanent settiements and com-
Regarding their economic geographical properties,
munication system are situated on the border
of the flooded surface, agricultural land lies
* lnstitut za raziskovanje krasa ZRC SAZU.
in the flood area too. Such poljes are:
YU-66230 POSTOJNA, Titov trg 2.
Imotsko, Popovo, Rastok, Jezero, etc.
1.3. Dry karst poljes in submediterranean belt are
exploitation the interventions into karst poljes can
regarding the size smaller but more fertile;
be divided to:
the lack of water diminishes their economic
2.1. Arrangement of water conditions for the need
value (Dugo polje, Dicmo, Ljubinje).
of agriculture and cattle-breeding production
1 4. Temporary flooded poljes in the mountainous
by either drying up or irrigation with local
continental part of Dinaric karst are regarding
use of water energy at springs and ponors.
the climatic and productive conditions more
2.2. Arrangement exclusively for energetic use by
suitable for cattle-breeding, either exclusively
construction of accumulation basins and arti-
as grassland and pasture ground or supple-
ficial outflow tunnels and energetic plants.
mentary agricultural surfaces for mainly cattle-
2.3. Arrangement for several purposes of water
breeding onented farms. The way of economic
economy use, agricultural, energetic and tou-
use is in great extent influenced by lasting
ristical ones and by limited coordination of
and annual variability of floods, but the agri-
ecological and landscape problems.
culture is limited too by the altitude and
2.4. Preservation.and consewation of natural un-
lower temperatures connected to climatic in-
changed properties in a form of reserves,
version. Beside cattle-breeding on the poljes
touristic curiosities or protected catchment
the woods are important on the poljes bor-
areas of water sources.
ders encouraging the woodworking industry.
1.5. Dry karst poljes in higher continental part of
Dinaric karst in between the wood belt are
3. Problems of karst poljes
suitable exclusively for grassland and cattle-
breeding (GlamoEko polje, Babno polje). The
wood on littoral mediterranean side is extre-
Forms, ways and problems of regulation and
mely degraded or even completely extinguish-
use of karst poljes are connected with:
ed because of exaggerated exploitation, as for
3.1. knowledge degree of karst phenomena and
example in Montenegro (Cetinje, Grahovo,
karst processes investigation rate on the sur-
face and in the underground of narrow and
Beside the agricultural function the poljes are
important because of their situation among higher
3.2. technical mastery degree of karst pheno-
karst ridges for their communication significance.
mena and their progress and ecological law-
Across them the old roads had been leading from
the interior towards the coast and back, modern
3.3. the expanse of interventions,
circulation communications, more roads than rail-
3.4. accordance and coordination of interventions
way, are there too. At cross-roa+ on poljes sma-
ller urban centres developed, being the industry
3.5. expected and secondary effects,
centres and causing new problems regarding pro-
3.6. cost of intewentions and other fees,
tection and management of karst.
3.7. valorization of natural properties in present
On some poljes of tectonic origin with Neo-
and in future, not yet known, economic and
gene lacustrine sediments there are stocks of
brown coa1 and lignite which are more and more
According to tasks and needs the research
important as energetic sources (Gacko polje). Su-
methods and technical interventions as well as the
perficial waters on dinaric poljes with common un-
organisational management demands have been
derground connections and possibilities for cons-
considerably ameliorated (Herak, 1972; Mikulec &
truction of greater accumulations on the different
~ r u m i c ,
1976; Milanovic, 1978).
altitudes present the main energetic potential of
Dinaric karst (TrebiSnjica system, Cetina).
4. lmproved research methods
2. The purpose of intervention
On the research area the efforts were directed
into the karst water regime
4.1. lnventarisation and classification and carto-
By social economic development and building
graphic documentation of the karst pheno-
industry progress as well as by research results the
mena in the poljes region as well as in their
human intewentions on karst poljes increased,
wider background. From this point of view
specially regarding their water regime by drying
were important geological, geographical
them up, partly by irrigation and mostly by exploi-
speleological investigations beside the
tation of available energetic potential. According to
4.2. Finding of water quantities, regime, precipita-
5.2. The attempts of simple water retention on
tion budget, inflow and outflow - for al1 these
poljes by closing up the swallow holes and
tasks the improved hydrometeorological ser-
by controlled water outflow into existent na-
vice has taken care.
tural conduits did not give the expected re-
4.3. Finding of underground water connections
sults either. The floods increased, threatened
on outflow side by corresponding springs
the agricultural surface and settlements on
and definition of catchment area on inflow
the border, the drying up started a little later
side. The water tracing methods were intro-
but has finished more quickly (CerkniSko je-
duced and improved (different tracers were
zero, HabiE, 1974).
used), somewhere in big quantities. Water
5.3. First serious attempts for permanent reten-
tracing methods were improved by interna-
tion of water on the karst poljes have been
tional collaboration of different institutions
furthermore conceived on superficial tightning
(1st - 5 th SUWT).
and isolation of the known swallow-holes. In
4.4. Study of cavernosity and permeability and
the alluvium inside the artificial accumula-
distribution of different hydrogeological .
tions have occurred new one ( ~ i k ~ i c ) .
units, complete, partial and hanging barriers,
5.4. The ill success forced the technicians to con-
influencing to distribution and direction of
ceive new methods for deep tightning of wa-
karst underground waters flow. From this
ter courses in karst. Practica1 realizations of
point of view the geological investigations by
deep injections in borders and under the su-
detailed mapping and boring, geomechanical
perficial dams have been sometimes accom-
and geophysical measurements and analyses
panied by surprises when big caverns have
contributed the most.
been hit by boreholes (Lika, BuSko blato) but
4.5. At first bigger technical interventions the
these problems have been promptly success-
planners had not taken enough care for natu-
fully solved. Supplementary investigations
ral and ecological investigations. They follow-
and tightnings have namely ricen the costs of
ed later, when the problems of preservation
the objects, but with rare exceptions, the fo-
of endemic subterranean animal specimens
reseen effects have been achieved (Mikulec &
have emerged, when the changed microcli-
~ r u m i c ,
matic conditions and troubles of human
adaptation to new conditions in life, empty
settlements, interrupted roads, disturbed
6. The meaning of karst
agrarian production and agricultural use and
other different results and changes in karst
ecosystem have occurred.
In the sphere of management and complex
landscape arranging an important progress has
been achieved. Exclusively energetic use of karst
5. Ways and effects of
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 & ~ r u m i c ,
1976). Agressive drainage of water
While planning and realizing the regulation
through the shortest artificial way from the moun-
projects some new methods have been introduced
tains to the sea, in spite of useful energetic objects,
just because of specific karst circumstances.
unabled the exploitation of precious karst waters
5.1. By previous cleaning and opening of ponors
for other purposes, water supply, irrigation, ecolo-
no essential ameliorations of poljes water re-
gical balance, sport and tourist activities etc. The
gime have been achieved; on one side a man
plans for several purposes use of karst waters and
wanted to avoid the floods while on the other
for available agricultural surfaces have been done,
he surpasses the lack of water in dry summer
which had diminished the energetic profit in behalf
months by difficulties (wells, rain-water, re-
of other users of water and space. On the other
servoirs). The majority of outflow tunnels,
hand such way had increased the costs of building
constructed on lower lying karst poljes (Je-
and indirectly the pcice of energy. Regarding the
zero, BokanjaEko blato, lmotsko polje, etc.)
fees only big, connected systems are acceptable
were not conceived on the real water condi-
(for example TrebiSnjica). At particular smaller pol-
tions, the planners did not consider enough
jes the costs of intervention were too high and the
the entire underground water system. Thus
effects too small. It is important specially when
the drought was increased but the floods were
considering unfavourable ecological consequences
not eliminated (Bonacci, 1985).
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-
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Conf. on the Hydraulics of Floods and Flood Control. BHRA.
ban and other economic uses of karst poljes. Clas-
Cambridge, p. 119-136.
sical karst poljes of Notranjsko, as are Cerknica and
CVIJIC, J. (1893): Das Kartsphanomen. Geogr. Abh. 5, H. 3, Wien,
Planina poljes should be, together with their envi-
p. 21 7-329.
ronrnent and several caves, arnong thern the world
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GAMS, 1. (1978): The polje: The problem of definition with special
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Stungart, p. 170-181.
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