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Environmental Earth Sciences
ISSN 1866-6280
Environ Earth Sci
DOI 10.1007/s12665-015-4090-7
Hydrogeology of the Skadar Lake basin
(Southeast Dinarides) with an assessment
of considerable subterranean inflow
Milan Radulovic, Micko Radulovic,
Zoran Stevanovic, Goran Sekulic,
Vasilije Radulovic, Mihailo Buric, Darko
Novakovic, et al.
1 23
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THEMATIC ISSUE
Hydrogeology of the Skadar Lake basin (Southeast Dinarides)
with an assessment of considerable subterranean inflow
Milan Radulovic •Micko Radulovic •Zoran Stevanovic •Goran Sekulic •
Vasilije Radulovic •Mihailo Buric •Darko Novakovic •Entela Vako •
Momcilo Blagojevic •Neda Devic •Dragan Radojevic
Received: 23 June 2014 / Accepted: 21 January 2015
ÓSpringer-Verlag Berlin Heidelberg 2015
Abstract The Skadar Lake basin is located in the south-
eastern part of the classical Dinaric karst region (northern
Mediterranean). This region is well known for its highly
developed karst and the presence of all types of karstic
features. In addition to the high degree of karstification, the
advantage of Skadar Lake’s catchment area in terms of
water resources is also reflected in the following factors: a
large amount of precipitation, scarcity of soil and vegeta-
tion cover, favourable geological and geomorphological
conditions for karst aquifer discharge, the isolation of the
Skadar basin from the influence of the Adriatic Sea and an
availability of water for simple abstraction. For the pur-
poses of a more complete determination of the water
balance of Skadar Lake, among other undertakings, it has
been necessary to determine the groundwater inflow to the
lake through numerous sublacustrine springs (vruljas). By
using thermal infrared satellite and terrestrial imaging, the
locations of the largest sublacustrine springs have been
detected and their yield assessed by means of water balance
calculation after the application of the KARSTLOP
method. The mean annual groundwater inflow to the lake,
from the south-western edge only, is 9.86 m
3
/s. The total
outflow of water from the lake through the Bojana River is
around 304 m
3
/s. The coincidence of several important
natural factors leads to the large average specific yield (-
surface and subsurface) in the Skadar Lake catchment area
M. Radulovic (&)M. Radulovic G. Sekulic
Faculty of Civil Engineering, University of Montenegro,
Cetinjski put bb, 81000 Podgorica, Montenegro
e-mail: radulovicmilan33@yahoo.com
M. Radulovic
e-mail: mickor@ac.me
G. Sekulic
e-mail: sgoran2000@gmail.com
Z. Stevanovic
Department of Hydrogeology, Faculty of Mining and Geology,
Centre for karst hydrogeology, University of Belgrade, Djusina
7, 11000 Belgrade, Serbia
e-mail: zstev_2000@yahoo.co.uk
V. Radulovic N. Devic D. Radojevic
Geological Survey of Montenegro, Naselje Krus
ˇevac bb,
81000 Podgorica, Montenegro
e-mail: geozavod@t-com.me
N. Devic
e-mail: nedad@mail.com
D. Radojevic
e-mail: dradojevi@yahoo.com
M. Buric
Faculty of Philosophy, University of Montenegro, Danila
Bojovic
´a bb, 81400 Niks
ˇic
´, Montenegro
e-mail: mihailo44@yahoo.com
D. Novakovic
Hydrometeorological Service of Montenegro, IV proleterske 19,
81000 Podgorica, Montenegro
e-mail: darko.novakovic@meteo.co.me
E. Vako
Institute of Geosciences, Energy, Water and Environment,
Polytechnic University, Rruga ‘‘Don Bosko’’ 60, Tirana, Albania
e-mail: vakoentela@yahoo.com
M. Blagojevic
Ministry of Agriculture and Rural Development of Montenegro,
Sector for Water Management, Rimski trg 46, 81000 Podgorica,
Montenegro
e-mail: moblagojevic@gmail.com
123
Environ Earth Sci
DOI 10.1007/s12665-015-4090-7
Author's personal copy
(54 l/s/km
2
), which makes this region one of the richest
areas of freshwater in the world.
Keywords Hydrogeology Karst aquifer Subterranean
inflow Skadar Lake
Introduction
Carbonate rocks (limestone and dolomite) have a wide
distribution in the Mediterranean region, especially in the
area of the Dinarides (the Dinaric Alps) which is known for
its well-developed ‘‘classical’’ karst. In the catchment area
of Skadar Lake, carbonate rocks cover around 70 % of the
surface and thus the karst aquifer is very important for this
area. Of the total quantity of water abstracted from the
catchment area for water supply, around 80 % is abstracted
from the karst aquifer. The rest of the water comes from the
intergranular aquifer, which is mostly recharged through
subterranean inflow from the adjacent karst aquifer.
This is an area which is very rich in karst waters, but
despite the abundance of water it is well known that the
discharge from karst springs decreases significantly in the
summer months. During the dry period, the intergranular
aquifers play an important role. In the rainy period, porous
intergranular aquifers receive large amounts of water from
the karst aquifer and retain it throughout the dry period.
When discharge from karst springs decreases in late sum-
mer, the required amount of water can be obtained from the
intergranular aquifers.
The Skadar basin is located in the south-eastern part of
the Dinarides (Fig. 1), i.e. in the northern Mediterranean
region. A significant part of the Skadar basin is covered by
the waters of Skadar Lake, which is the largest in the
Balkan Peninsula. It is a transboundary lake, belonging
partly to the territory of Montenegro (around 65 %) and
partly to that of Albania (around 35 %). The catchment
area of Skadar Lake covers 5,631 km
2
, measured to the
hydrometric station (HS) ‘‘Skadar’’. Around 81 % of the
catchment area belongs to the territory of Montenegro, with
the rest in the territory of Albania.
Skadar Lake and its surrounding area comprise a very
important aquatic ecosystem. Since 1996, this area has
been included in the Ramsar list of wetlands of interna-
tional importance. The cold groundwater which outflows
through a number of sublacustrine springs (vruljas) is of
great importance for the aquatic biota of Skadar Lake.
The geology of the region has been studied by many
researchers both at home and abroad (Tietze 1884; Bal-
dacci 1886; Hassert 1895; Cvijic
´1899; Nopcsa 1916;
Bourcart 1926; Waisse 1948; Milovanovic
´1965; Bes
ˇic
´
1969; Grubic
´1975; Mirkovic
´et al. 1985).
Also, numerous hydrogeological studies have been
carried out in the Skadar Lake catchment area (Torbarov
and Radulovic
´1966; Radulovic
´1989,2000,2012; Radu-
lovic
´et al. 1979,1989,1998; Zogovic
´1992; Buric
´1993;
Radulovic
´and Radulovic
´2004; Stevanovic
´et al. 2008;
Djordjevic
´et al. 2010; Devic
´2011; Sekulic
´and Bushati
2013).
Very little has been written in English regarding the
hydrogeology of the Skadar Lake basin, and one of the
objectives in writing this paper is to present this water-rich
region to the wider scientific community. For this purpose,
the hydrogeological characteristics of this area are de-
scribed. Also, data pertaining to water balance components
has been collected and evaluated. In addition, for the first
time a comprehensive assessment of the subterranean in-
flow into the lake from the south-western and the northern
edge of the lake has been conducted.
Hydrogeological characteristics of the Skadar Lake
catchment area
Climate and hydrography
The wider area of the Skadar basin has a modified
Mediterranean climate with hot and dry summers and cold
winters. The mean annual air temperature in the catchment
area ranges from 4 to 12 °C.
The main factors leading to a large amount of pre-
cipitation in this area are its position in relation to the
Adriatic Sea and the configuration of the terrain. The mean
annual amount of precipitation for the catchment area of
Skadar Lake is approximately 2,500 mm.
Skadar Lake is elliptical in shape, elongated in an NW–
SE direction, with the length of the longer axis at ap-
proximately 26 km and the shorter axis around 12 km. The
average level of the lake is 6.52 masl. The volume of the
lake ranges from 1.75 km
3
(at the minimum water level of
4.54 masl) to 4.25 km
3
(at the maximum water level of
10.44 masl).
Several rivers flow into Skadar Lake (Fig. 1), but the
Morac
ˇa River has the highest discharge. Around 63 % of
the total water inflow to the lake comes via the Morac
ˇa
River. The lake also receives significant amounts of water
directly from the coastal aquifer. The lake is drained by the
Bojana River, which flows out of the lake on the southeast
side. After a few kilometres the Bojan River receives the
Drin River from the east, which in particular hydrological
situations creates a hydraulic barrier for the waters that
flow out from the lake. The Bojana River, after a journey of
42 km, flows into the Adriatic Sea close to the town of
Ulcinj.
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Geology
Carbonate rocks (limestone and dolomite) are dominant in
terms of their distribution in the catchment area of Skadar
Lake. On the geological map of Montenegro (Mirkovic
´
et al. 1985), these carbonate rocks are identified as Meso-
zoic sediments (Triassic, Jurassic and Cretaceous). Their
thickness in this area can be more than 5 km. Triassic,
Cretaceous and Eocene flysch and Triassic volcano-
sedimentary formations are also represented in this area
(Mirkovic
´et al. 1985), but with limited distribution. Karst
depressions are filled with clastic materials of different
origins (alluvial, glacial, fluvioglacial, lacustrine, eluvial
and diluvial sediments).
Four tectonic zones are distinguished in the wider area
of the Skadar basin (Mirkovic
´et al. 1985), the:
1. Paraautochton (Adriatic–Ionian) zone which extends
along the coast of the Adriatic Sea (this zone is mainly
represented by limestone and low permeable flysch);
2. Budva–Cukali zone which extends along a belt parallel
to the coast of the Adriatic Sea, between the Parahton
Fig. 1 Position of the Skadar
Lake catchment area on the
regional tectonic map
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and Visoki Krsˇ zones (this zone is a complex of rocks
that represent a hydrogeological barrier);
3. Visoki Krsˇ zone which extends over almost the entire
surface of the Skadar Lake catchment area (this zone is
mainly represented by limestone and dolomite which
are characterised by a high degree of karstification);
4. Durmitor zone which occupies the northern part of the
territory of Montenegro and Albania (this zone is
mainly represented by low permeable flysch sedi-
ments, but limestone also extends in certain areas).
The tectonic zones mentioned above are separated by
reverse faults with a general orientation northwest–south-
east, so that the Durmitor tectonic zone is pushed up over
the Visoki Krsˇ zone, this over the Budva–Cukali zone and
that over the Paraautochton zone (Fig. 1).
A system of folds extends along the same Dinaric di-
rection (NW–SE) (Fig. 1). Within the Visoki Krsˇ tectonic
zone, there are two regional anticlines between which,
along sizeable karst depressions, one regional syncline
stretches (Bes
ˇic
´1969).
Geomorphology
From the geomorphological point of view, the regional
anticlines mentioned above take the form of two wide karst
plateaus with a syncline between them containing a system
of karst depressions: Skadar basin–Zeta valley–B-
jelopavlic
´i valley–Niks
ˇic
´polje–Duga gorge.
The karst depression of the Skadar basin, Zeta valley
and Bjelopavlic
´i valley (Figs. 1and 2), is one of the largest
karst depressions in the area of the Dinarides. This de-
pression is filled with unconsolidated clastic deposits up to
100 m thick. Skadar Lake is a crypto depression, when we
consider the fact that the southern part of the lakebed is
around 2 m lower than sea level (the lakebed is sig-
nificantly deeper at the locations of the underwater dolines,
where depths reach up to 66 m below sea level). The
altitude of the Zeta–Bjelopavlic
´i karst depression ranges up
to 80 masl, and the altitude of the Skadar basin is up to
175 masl in its eastern part. The next depression to the
north-west is Niks
ˇic
´polje, which has a much higher alti-
tude (about 630 masl). The polje is separated from Bjelo-
pavlic
´i valley by a high limestone crest. The direction of
the system of karst depressions is accompanied by a narrow
zone of impervious flysch sediments, which in one part
extends beneath clastic material, part way along the de-
pression edge.
The karst plateau, which extends south-west from this
system of depressions, is characterised by the development
of nearly all karst landforms. There are a number of
sinkholes which often form a polygonal karst. There also
exist more sizeable karst depressions such as uvalas, poljes
and dry valleys. This area is characterised by the devel-
opment of a subsurface network of karst conduits. Another
karst plateau that extends north-east from the great de-
pression (Fig. 2), in addition to the development of surface
and subsurface karst landforms, is also characterised by the
existence of deep karst canyons (the canyons of the Morac
ˇa
River, Mrtvica River, Mala River, Cijevna River, Thata
River and Rrjoli River). The average altitude of karst
plateaus within the catchment area of Skadar Lake is
938 masl.
Groundwater
The karst aquifer has a wide distribution in the Skadar Lake
catchment area. It is presented in the area of the karst
plateau, but also at the base of the aforementioned de-
pressions. Significant importance can be ascribed, espe-
cially in the dry period of the year, to the granular aquifer
of Zeta valley and the Skadar basin, which is formed in the
high-permeable gravelly sandy sediments. Regarding the
low-permeable sediments, there is a flysch and volcano-
sedimentary formation which represents an aquitard, i.e. a
barrier to groundwater. The lacustrine sediments, which fill
parts of the karst depressions, also have a very low
permeability.
Generally, the recharge area of the karst aquifer is
spread over a wide area in the karst plateaus, while the
discharge area extends along the karst depressions and
deep canyons (Fig. 2). The average difference in elevation
between the recharge and discharge area is around 800 m.
Recharging of the karst aquifer occurs mainly through
atmospheric water infiltration. It is interesting that despite
such a large amount of precipitation (an average of about
2,500 mm/year), surface waters are almost completely
absent from the recharge area. This is primarily due to the
high permeability of the carbonate rocks and the specific
geomorphology of karst terrains. When waters from rain-
fall reach such a surface, they rapidly infiltrate into the
ground before they reach a level high enough to concen-
trate in significant streams. The surface concentration of
waters in the recharge area occurs only in two cases. In the
first, limited surface concentration can take place in local
karst depressions (the larger sinkholes, uvalas, poljes or dry
valleys), where springs usually occur along one edge and
swallow holes along another edge. In the second case, a
significant surface concentration of water is achieved in
terrains where the rivers come from impervious flysch
terrains, as is the case in the north-eastern part of the
catchment area.
Generally, groundwater flows from the recharge area to
the regional syncline depressions and deep canyons. The
fold tectonic has an impact on the flow directions of
groundwater, particularly in areas where the cores of the
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anticlines are composed of less permeable rocks (cemented
clastites or less permeable dolomites). However, in areas
where the cores of the anticlines are also composed of
karstified limestones, the impact of the fold tectonic is ir-
relevant to the flow directions of groundwater.
Groundwater flow occurs mainly along major faults,
along which karst channels have usually developed. The
network of karst channels is well developed, as confirmed
by numerous indicators, both direct (the results of speleo-
logical survey, drilling and permeability tests) and indirect
(significant fluctuations in springs discharge, rapid reac-
tions in terms of spring discharge after rainfall, turbidity in
the spring water after intensive rainfall events, rapid
recession of spring discharge in the dry period, negative
values for the saturation index of spring water and the high
velocity of artificial tracers) (Radulovic
´2012).
Regarding the issue of the subsurface karst network
development in the vertical direction, two zones can be
distinguished. The upper zone, besides showing the de-
velopment of narrow corrosion karst channels, is charac-
terised by the development of spacious fluvial caves
(Fig. 3). The output channels of spring caves can be of the
descending type, as is the case with Crnojevic
´a cave
(Fig. 3a), or the ascending type, where the cave channels
may even be partly below the level of the regional base of
erosion, such as in the case of the submerged cave channels
Fig. 2 Map of recharge and
discharge areas of the karst
aquifer in the Skadar Lake
catchment area
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of Karuc
ˇBay (Fig. 3b). The lower zone, which is charac-
terised only by the presence of narrow corrosion channels,
extends from the level of the lowest fluvial caves to great
depths. By drilling a deep exploration borehole in the
Niks
ˇic
´Z
ˇupa (750 masl), karstification was even detected at
a depth of 2,070 m below the surface (Radulovic
´2000), i.e.
at a depth of 1,320 m below sea level.
Discharge from the karst aquifer mainly occurs along
the edges of synclinal depressions. In addition to the tec-
tonic and geomorphological predisposition of the karst
aquifer for discharge, the spatial position of impervious
flysch sediments also plays an important role. Flysch ex-
tends along the direction of sizeable karst depressions,
from the north-western part of the catchment area to the
surroundings of Skadar Lake in the south-eastern part.
Since deep canyons intersect the north-eastern karst plateau
in several places, discharge from the karst aquifer in the
rainy period also occurs along these canyons. In the dry
season, when the groundwater level drops below the bot-
tom of the canyons, river begins to sink and partly continue
to flow in a subterranean way towards the nearest edge of
the karst depression.
In the catchment area of Skadar Lake, there are over
200 registered karst springs. According to yield and im-
portance for this area, the following springs stand out
(listing from the northwest to the southeast; Fig. 2):
Vidrovan springs, Rastovac springs, Poklonci spring,
Slano spring, Obos
ˇnica spring, Glava Zete spring, Do-
bropolje spring, Milojevic
´i spring, Oras
ˇspring, Bijeli
Nerini springs, Vuc
ˇiji Studenci springs, Mareza spring,
Ribnicaspring,BoljeSestrespring,Karuc
ˇspring
(Fig. 3b), Crnojevic
´a spring (Fig. 3a), Vitoja spring,
Podgor spring, Velji spring, Radus
ˇspring, Krnjice spring
(territories of Montenegro), Syri Sheganit spring, Rrjolli
spring and Vraka spring (territories of Albania).
The karst aquifer partly discharges through a number of
sublacustrine springs. Most of these are presented by un-
derwater dolines from which groundwater flows directly
out into the lake. One of the deepest underwater dolines is
the Radus
ˇspring, which discharges 66 m below sea level.
Fig. 3 a Hydrogeological section of Lovc
´en–Crnojevic
´a spring, bhydrogeological section of Os
ˇtro hill–Karuc
ˇ
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As well as through temporary and permanent karst
springs, discharge from the karst aquifer also occurs by
means of subterranean outflow into the fluvioglacial and
alluvial sediments of Zeta valley and Skadar basin. In this
way, the intergranular aquifer receives and accumulates a
significant amount of groundwater, which can be abstracted
intensively in the driest period of the year.
Estavelles are distributed along the edges of the Niks
ˇic
´
and Cetinje poljes, as well as in the downstream parts of
the Morac
ˇa and Cijevna canyons. In the rainy period of the
year, these phenomena serve as karst springs, while in the
dry period they function as swallow holes (ponors).
The karst aquifer of the Skadar Lake catchment area is
characterised by significant fluctuations in groundwater
levels and the discharge of karst springs. In the area of the
Niks
ˇic
´and Cetinje poljes, fluctuations in the level of
groundwater can be up to 200 m (Vlahovic
´1975; Radu-
lovic
´2000). Significant fluctuations in yield, as well as
rapid response to rainfall, can be seen from the hydrograph
of the Crnojevic
´a spring (Fig. 4).
In the catchment area of Skadar Lake, there is high-
quality low-mineralised groundwater. Given that ground-
water mainly flows through limestone and dolomite, it has
increased concentrations of HCO
32-
,Ca
2?
and Mg
2?
ions.
Its pH value ranges from 6.95 to 7.80 (Devic
´2011).
Methodology for the assessment of subterranean inflow
It is well known that this area is rich in freshwater, but
since conditions for the realistic assessment of water re-
sources are highly complex, a clear water balance for
Skadar Lake has for a long time remained undefined. In
addition to surface inflow, a significant amount of water
comes into the lake through subterranean paths.
The inflow of surface waters was relatively easy to de-
termine by means of discharge measurements. The largest
amount of water comes into Skadar Lake through the
Morac
ˇa River. In addition to the Morac
ˇa River, there are a
large number of small streams which also feed the lake
with water (Fig. 1).
However, the inflow of groundwater into the lake was
extremely difficult to determine, because the use of con-
ventional methods for determining the balance elements of
the karst aquifer in these terrains is almost impossible. The
main difficulties in the assessment of subterranean inflow
into the lake are as follows:
– a lack of knowledge related to the locations sublacus-
trine springs (vruljas),
– an inability to measure the discharge of known
sublacustrine springs and
– an inability to measure the representative value of
effective infiltration by classical point methods
(lysimeter, zero-flux plane) in the catchment areas of
sublacustrine springs, since these are very heteroge-
neous karst terrains.
To overcome the problem of locating the sublacustrine
springs, infrared thermography techniques, which are
based on the detection of temperature anomalies on the
lake surface, were applied. The temperature anomalies
appear at locations where there are discharges of colder
groundwater below the surface of the warmer lake water,
i.e. at the locations of sublacustrine springs. First, the
anomalies are detected in thermal infrared satellite images
of lower resolution (Landsat ETM?Band 6; resolution
Fig. 4 Hydrograph of
Crnojevic
´a spring discharge
(hydrometric station ‘‘Brodska
Njiva’’) with precipitation bar
graph (climatological station
‘‘Cetinje’’) (after Z
ˇivaljevic
´
1991)
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60 m), one of which is shown in Fig. 5, and then with
terrestrial imaging using a handheld thermal infrared
camera (Fig. 6).
It was found that the majority of sublacustrine springs
appear on the south-western edge of the lake. After hy-
drogeological studies, the catchment area boundaries of the
south-western edge of the lake were delineated. Since there
are a number of rain gauges in this area, the mean annual
precipitation can also be determined reliably. For the pur-
pose of assessing the groundwater outflow through subla-
custrine springs on the south-western edge, it was also
necessary to determine the average value of effective in-
filtration (recharge rate) for this karst area.
This was done by applying the KARSTLOP method,
which has been specially developed for determining the
spatial distribution of recharge in highly karstified terrains
(Radulovic
´et al. 2012). The method is based on the
mapping of natural factors that have the greatest influence
on recharge of the karst aquifer. By overlapping the eight
maps (layers) of selected factors applying GIS techniques
and using the appropriate algorithm, a final map showing
the spatial distribution of the mean annual effective
Fig. 5 Map showing the
temperature of the surface of
Skadar Lake, obtained by
satellite image LANDSAT 7
ETM?(thermal infrared
band—Band 6; resolution 60 m;
date of capturing: 23 April
2002). The temperature
anomalies (blue tones) indicate
the locations of some
sublacustrine springs, where
colder groundwater discharges
below the lake level
Fig. 6 a Photo of Karuc
ˇbay captured in the visible spectrum. bPhoto of Karuc
ˇbay captured in thermal infrared spectrum, from which a
temperature anomaly can be seen (purple tones), i.e. the main location of groundwater discharge
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infiltration expressed as a percentage of precipitation is
obtained.
Before applying this method to the south-western edge
of Skadar Lake, it was tested and calibrated according to
four similar catchment areas of nearby terrestrial karst
springs, for which all of the water balance elements have
been determined through previous research (Z
ˇivaljevic and
Bos
ˇkovicic 1984;Z
ˇivaljevic
´1991; Zogovic
´1992; Radu-
lovic
´1994,2000; IJC 2001).
For the assessment of the diffuse inflow of groundwater
from the granular aquifer along the northern edge of the
lake, the mathematical model MODFLOW (McDonald and
Harbaugh 1988), which was developed for the wider area
of the Zeta valley, was used (Radulovic
´et al. 2013).
Assessed subterranean inflow within the total water
balance of Skadar Lake
In the process of determining the water balance of Skadar
Lake, the most difficult aspect was assessing groundwater
inflow from the south-west and the northern edge of the
lake.
After applying the KARSTLOP method to the south-
western edge of Skadar Lake, a digital map of effective
infiltration was obtained (Fig. 7). Based on this map, the
average effective infiltration in the catchment area of the
south-western edge was assessed as amounting to 68.5 %
of precipitation. Knowing the size of the catchment area
(185 km
2
) and the mean annual precipitation (2,461 mm),
water balance calculations suggest that the mean annual
sublascustrianin flow from the south-western edge of the
lake is 9.86 m
3
/s.
MODFLOW modelling of the intergranular aquifer of
Zeta suggests that the inflow into the lake from the northern
side amounts to 11.62 m
3
/s (Radulovic
´et al. 2013).
It was possible to determine other inflows on the basis of
previous hydrological measurements and assessments of
discharge specified in various references (Table 1). Table 1
gives an overview of the Skadar Lake water balance ob-
tained on the basis of previous and new data.
Assessed subterranean inflows from the south-western
and the northern edge of the lake are not inconsistent with
the other components of the Skadar Lake water balance.
However, there are some uncertainties as to the total water
balance that are discussed in the following section.
Uncertainties about quantification of water resources
in the Skadar Lake basin
Even after assessing subterranean inflows from the south-
western and the northern edge of the lake, there remain
some uncertainties as to the other mean annual water bal-
ance components.
The inflow from the Albanian side requires further
analysis because data pertains exclusively to the total in-
flow (Table 1).
Since the karstic springs and hydrometric stations in
Malo Blato Bay, Karuc
ˇBay, Hot Bay and Hum Bay are
Fig. 7 Map of the spatial
distribution of recharge
obtained by means of the
KARSTLOP method for the
catchment area of sublacustrine
springs on the south-west edge
of Skadar Lake
Environ Earth Sci
123
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flooded by high lake water, there are also discrepancies
regarding the results of discharge measurements at these
stations (Table 1).
The difference between the total known output and
the total known input is 5.58 m
3
/s (Table 1). There are
two possible explanations for this discrepancy. First,
there is inflow through unknown sublacustrine springs
and, second, there is inflow from Drin River during its
high levels.
Based on a rough estimation, the total subterranean in-
flow (assessed inflows from the south-western and northern
edge, discharges measured at hydrometric stations sub-
merged when the level is high, subterranean inflow from
the Albanian side assessed by analogy and unknown in-
flows) amounts approximately 55 m
3
/s, i.e. around 17 % of
the total inflow into the lake.
It is extremely difficult to determine storage for the karst
aquifer because of a lack of data related to the permeability
and effective porosity of carbonate rocks and the depth to
the base of karstification. However, bearing in mind that
karst channels are developed to great depths, even deep
below sea level, it can be concluded that a large amount of
groundwater is stored.
The storage of the granular aquifer, which is mainly
recharged by karst waters, can be assessed reliably because
the base of the aquifer has been well defined thanks to the
drilling of a large number of exploration boreholes
(Radulovic
´et al. 2013). Also, the porosity of gravelly
sandy material has been determined reliably in the course
of performing a large number of field and laboratory tests
(Radulovic
´et al. 2013). On the basis of existing data, it can
be concluded that within the granular aquifer quite a large
amount of groundwater has accumulated. For example,
static reserves (storage) of the Zeta valley granular aquifer
alone amount to around 3 km
3
.
To obtain a better quantification of water resources in
the Skadar Lake basin, more detailed hydrological and
hydrogeological studies are required.
Conclusion
The catchment area of Skadar Lake, measured by the value
of average specific yield (surface and subsurface), which
amounts to as much as 54 l/s/km
2
, makes it one of the
richest areas of freshwater in the world.
Several important natural factors, which have a bearing
on such a large quantity of fresh water flowing out from the
catchment area and accumulating in the Skadar Lake basin
and Zeta valley, coincide in these terrains. Listed below are
the main conveniences of the Skadar Lake catchment area
in terms of water potentiality:
Table 1 The water balance of Skadar Lake (mean annual values)
No. Inflow/outflow (description) Inflow/outflow
(m
3
/s)
References
1 Inflow by Morac
ˇa River (at the mouth) 201 IJC (Institut Jaroslav
Cerni) (2001)
2 Inflow from Malo Blato bay (River Bis
ˇevina, HS ‘‘Nikolin Mlin’’) 11.75 Radulovic
´et al. (1979)
3 Inflow from Karuc
ˇbay (Bazagur River, HS ‘‘Bazagur’’) 7 Zogovic (1992)
4 Inflow by Crnojevic
´a River (HS ‘‘Brodska Njiva’’) 6.15 IJC (Institut Jaroslav
Cerni) (2001)
5 Inflow by Poseljani River and Modro Oko 2.5 Radulovic
´et al. (1998)
6 Inflow by Orahovs
ˇtica River (HS ‘‘Orahovo’’) 3.53 Radulovic
´et al. (1998)
7 Inflow by Crmnica River 2.51 Radulovic
´et al. (1998)
8 Inflow from the south-western edge through sublacustrine karst springs 9.86 Radulovic
´(2012)
9 Inflow from the granular aquifer of Zeta valley 11.62 Radulovic
´et al. (2013)
10 Inflow from Hum bay and the Montenegrin part of Hot bay 2.5 Radulovic
´et al. (2013)
11 Inflow into the lake from the Albanian side 36 Prohaska et al. (2004)
12 Inflow by precipitation directly on the lake 20 Bos
ˇkovic
´et al. (2006)
13 Total known inflow into the lake (sum of the upper rows) 314.42 –
14 Outflow through Bojana River 304 Bos
ˇkovic
´et al. (2006)
15 Outflow through evaporation from the lake surface 16 IJC (Institut Jaroslav
Cerni) (2001)
16 Total known outflow from the lake (14 ?15) 320 –
17 Unknown inflow into the lake (16-13) (unknown sublacustrine springs or possible inflow
from the Drin River when its level is high)
5.58 –
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– A large amount of precipitation falls in the recharge
area of the karst aquifer.
– A significant percentage of atmospheric water infil-
trates deep into the ground very quickly after rainfall
events, so that only a small amount of water remains
for evapotranspiration. This high value for effective
infiltration is a consequence of the high permeability of
the rocks and the specific geomorphology of the karst
terrains, as well as the absence of soil and vegetation
cover for a significant part of the area.
– Conditions for karst aquifer discharge are highly
favourable as there is a significant depth of depressions
permitting karst aquifer, a favourable tectonic and
spatial position of aquitards.
– The Skadar basin is separated from the Adriatic Sea
basin by the impervious tectonic Budva–Cukali zone,
so that the salinisation of groundwater is not possible.
– Large amounts of karst waters accumulate within the
granular aquifer of the Zeta valley and the Skadar
basin, so that they are easily available for abstraction
and further distribution.
This paper can be used as one of the bases for future
projects to be created by researchers, environmentalists,
planners and designers of hydraulic engineering works
which are planned in the Skadar Lake basin.
Due to the importance of karst waters for the wider area
of the Skadar basin, it is necessary to devote greater at-
tention to this issue to ensure the adequate protection and
use of this precious natural resource.
Acknowledgments We would like to thank our friends Dr. Aidan
Foley, Travis Hostetter and Jonathan Griffiths, who helped us a great
deal with proofreading this paper.
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