FACTORS INFLUENCING THE GROUNDW ATER CIRCULATION IN MALI ME GROPA KARST MASSIF, CENTRAL ALBANIA DEJAVNIKI, KI VPLIV AJO NA PODZEMNO VODO IN NJENO KROŽENJE V KRAŠKEM MASIVU MALI ME GROPA V OSREDNJI ALBANIJI Romeo EFTIMI 1 , Viacheslav ANDREYCHOUK 2 , Peter MALÍK 3 , Tatiana OREHOV A 4 , Małgorzata NITA 5 & Perikli QIRIAZI 6 Abstract UDC 551.44:556.33(496.5) Romeo Eftimi, Viacheslav Andreychouk, Peter MalÍK, Tatia- na Orehova, Małgorzata Nita & Perikli Qiriazi: Factors influ- encing the groundwater circulation in Mali me Gropa karst massif, Central Albania There are 23 carbonate karst areas in Albania with a total area of 6440 km 2 , or 24% of the country’s territory. Karst aquifers are the richest in the country and about 80% of the water supply for the population living in cities is supplied by karst water. One of the most interesting karst massifs of Albania is called Mali me Gropa (MMG) with a total surface area of 157 km 2 . It is the subject of this paper. Although this massif has attracted atten- tion due to its exceptional development of surface karst land- forms (karst pits, sinkholes, swallow holes) and its large and high-quality groundwater resources, it has not been the subject of comprehensive research. In this paper, for the first time, is a summary of the results of a combination of specialized stud- ies, including geomorphological characterization, analysis of long-term groundwater regime observations in relationship with meteorological data, water balance studies applying the re- cently developed WaterbalANce software method, assessment of groundwater quality and its variability, determination of the groundwater flow velocity with an artificial tracer, and the use of hydrochemistry and runoff data to determine groundwater flow patterns and sensitivity of spring water to contamina- tion. The results of the multi-method studies conducted on the MMG karst massif will inform future studies of the numerous Izvleček UDK 551.44:556.33(496.5) Romeo Eftimi, Viacheslav Andreychouk, Peter MalÍK, Tatia- na Orehova, Małgorzata Nita & Perikli Qiriazi: Dejavniki, ki vplivajo na podzemno vodo in njeno kroženje v kraškem ma- sivu Mali me Gropa v osrednji Albaniji V Albaniji je 23 karbonatnih kraških območij s skupno površino 6.440 kilometrov 2 ali 24 % ozemlja države. Kraški vodon- osniki so najbogatejši v državi, s kraško vodo pa se oskrbuje približno 80 % prebivalcev mest. Eden izmed najzanimivejših kraških masivov v Albaniji se imenuje Mali me Gropa s skupno površino 157 kilometrov 2 . Ta je jedro tega članka. Čeprav je ta masiv z izjemnim razvojem površinskih kraških oblik (kraške jame, vrtače, požiralniki) ter z velikimi in visoko kakovostnimi viri podzemne vode pritegnil pozornost, še ni bil predmet ce- lovite raziskave. V tem članku so prvič povzeti rezultati kom- binacije specializiranih študij, kot so geomorfološka karakter- izacija, analiza dolgoročnih opazovanj režima podzemne vode v povezavi z meteorološkimi podatki, študije vodnega ravnovesja z uporabo nedavno razvitega programa WaterbalANce, ocena kakovosti podzemne vode in njene spremenljivosti, določitev hitrosti toka podzemne vode s poskusom z umetnim sledilom ter uporaba hidrokemičnih podatkov in podatkov o iztoku podzemne vode, za določitev vzorcev toka podzemne vode in občutljivosti izvirske vode na onesnaženje. Rezultati raziskav, izvedenih z več metodami in na kraškem masivu Mali me Gro- pa bodo podlaga za prihodnje raziskave številnih karbonatnih kraških območij v Albaniji. Zadnji pomembni cilj tega članka ACTA CARSOLOGICA 54/2-3, 155-172, POSTOJNA 2025 1 Independent Researcher, Rr. Rreshit Çollaku, pll. 10/3/18, Tirana, Albania, e-mail: eftimiromeo@gmail.com 2 Akademia Bialska im. Jana Pawła II, Sidorska 95/97, 21-500 Biała Podlaska, Poland, e-mail: czeslaw.andrjczuk@gmail.com 3 Štátny geologický ústav Dionýza Štúra - Geological Survey of Slovak Republic, Mlynská dolina 1, 817 Bratislava 11, Slovakia, e-mail: peter.malik@geology.sk 4 Climate, Atmosphere and W ater Research Institute at Bulgarian Academy of Sciences, Sofia, Bulgaria, e-mail: tvorehova@gmail.com 5 Faculty of Natural Sciences, Institute of Earth Sciences, University of Silesia in Katowice, Będzińska 60, 41-200 Sosnowiec, Poland, e-mail: malgorzata.nita@us.edu.pl 6 Geographical Research Unit, Academy of Sciences of Albania, e-mail: perikli.qirjazi@gmail.com Received/Prejeto: 15. 3. 2025 DOI: https://doi.org/10.3986/ac.v54i2.14389 ROMEO EFTIMI, VIACHESLAV ANDREYCHOUK, PETER MALÍK, TATIANA OREHOV A, MAŁGORZATA NITA & PERIKLI QIRIAZI 1. INTRODUCTION Karst aquifers provide drinking water to almost a quarter of the world population (Hartmann et al., 2014; Bakalow- icz, 2005; Chen et al., 2017; Stevanović, 2015, 2019). They are used even more extensively in the Mediterranean area (Margat, 1998; Bakalowicz, 2015; Günay & Ekmekci, 2015; Stevanović, 2019; Liso & Parise, 2020). Southeastern Eu- rope is one of the most water-rich regions of the world and some large cities like Rome, Vienna, Rijeka, Dubrovnik, Sarajevo, Skopje and Tirana are supplied with water from karst sources (Stevanović & Eftimi, 2010). Albania is characterised by a wide presence of karst aquifers. The karst rocks in Albania cover about 6750 km 2 , which is about a quarter of Albania’s territory. They form 23 carbonate karst regions and two evapo- ritic regions (Eftimi, 2020). The estimated natural karst groundwater resources of Albania consist of 227 m 3 /s, while the exploitable groundwater resources are about 90 m 3 /s (Eftimi, 2010). The Mali me Gropa Mountain (in Albanian, "The Mountain with Holes"), further referred to as MMG, is of extraordinary practical and scientific importance. The practical importance of this massif is re- lated to the large and very good quality of groundwater resources, which mostly discharge as large springs. The scientific value of the study of MMG massif is related to the exceptional karstification of this massif and the rela- tion of this to the quantitative and qualitative character- istics of the groundwater. Location of the springs in relation to tectonics and karst morphology, as well as the use of karst water quality and of the regional flow type and groundwater sensitivity to pollution of the karst massif, are particularly discussed in this paper. carbonate karst regions in Albania. A final important objective of this article is to raise public awareness about the vulnerability of karst waters and the need to protect the associated ecosys- tem, especially now that the MMG karst massif is in the spot- light for tourism development. Keywords: MMG karst massif, spring’s regime, effective pre- cipitation, water resources, Albania. Figure 1: Location map. A Eu- rope; B Karst aquifers of Albania (after Eftimi at al., 1985) and lo- cation of study area. je ozaveščanje javnosti o ranljivosti kraških voda in nujnosti zaščite povezanega ekosistema, zlasti zdaj, ko je kraški masiv Mali me Gropa v središču pozornosti zaradi razvoja turizma. Ključne besede: kraški masiv Mali me Gropa, režim izvirske vode, efektivne padavine, vodni viri, Albanija. 156 ACTA CARSOLOGICA 54/2-3 – 2025 FACTORS INFLUENCING THE GROUNDW ATER CIRCULATION IN MALI ME GROPA KARST MASSIF, CENTRAL ALBANIA 2. STUDY AREA The karst massif of MMG is located in Central Albania, about 20 km north-east of Tirana (Figure 1). Against the backdrop of its surroundings, this massif creates quite a compact area in which the elevation varies about 1500- 1800 m above sea level (a.s.l.) and dominates 400 to 1000 m a.s.l. above the surrounding valleys. It is built mostly of Mesozoic limestone overthrown on a Paleogene flysch formation. The massif extends for 15-18 km from west to east, and 5-11 km from south to north, while its area is ~157 km 2 large. Linos’s valley, dipping gently from south to north, geographically separates the MMG into western and eastern blocks (Figure 2). 2.1 CLIMATE AND HYDROLOGY According to the classification of the Institute of Hydro- meteorology of Tirana (Jaho et al. 1975), the climate of the study area is mountainous Mediterranean. T o charac- terize the precipitation and air temperature regime, data from the meteorological stations of Selita Malit (810 m a.s.l.) on the Western Plateau and Lena Martanesh (1000 m a.s.l.) on the periphery of the Eastern Plateaus were used (Figure 2). The average precipitation and air tem- perature values for the Western Karst Plateau are 2100 mm and 6.5° C, respectively, as interpolated from values measured at Selita meteorological station. For Lena sta- tion with consideration of its altitude the corresponding values are 1600 mm and 10 °C. According to the data for the observation period 1961-1985, for the 6-month period (from October to March) in Selita station, the average amount of precipita- tion is 1470 mm, or 67% of the annual amount; and for the period April-September, it is 680 mm, or 33% of the annual amount. During a period of about 50-60 days per year, the air temperatures fall below zero and the plateaus are snow-covered. The maximal thickness of the snow cover is about 50-70 mm (Jaho et al., 1975). As often in karst areas (Ford & Williams, 2007; Bakalowicz, 2005; Eftimi, 2010), the surface hydrograph- ic network of the Mali me Gropa is not well developed and in contrary the subsurface hydrographic network is intensively developed. The only permanent river of the massif is the Mat River, which flows along a deep canyon in the eastern periphery of the MMG massif, in contact with the intrusive rocks (Figure 3). The karst groundwa- ter of the entire eastern part of the massif consisting of the Central and Eastern Plateaus practically drains into the canyon (Figure 3). Based on runoff measurements at the beginning and end of the canyon consisting of car- bonate rocks, it is estimated that a groundwater quantity of about 4.6 m 3 /s drains into the canyon of the Mat River. Another permanent river, the Biza River, whose water- shed is about 25 km 2 , is located in the southernmost part of the Vali valley. After flowing only about 300 m in this valley, the river disappears into the Vali Cave (Figures 2 and 3). The discharge of the Biza River, before disappear- ing in the cave, varies from zero to about 5-6 m 3 /s during very heavy rains, but the mean discharge is estimated at about 330 l/s (Figure 3). 2.2 GEOLOGICAL STRUCTURE Albania is part of the Mediterranean Alpine Folded Belt and the Dinaric-Hellenic range (Aliaj 2012; Meco & Aliaj, 2000; Xhomo at al., 2002). The MMG massif belongs to the Mirdita Zone, which is known also as the zone of magmatic rocks (Figure 1) and is equivalent of the Ser- bian Zone in the Dinarides and the Subpelagonian Zone Figure 2: Relief shadow model of the MMG karst massif, karst pla- teaus and main karst springs, us- ing shading and colour model as visualization tools to show the ter- rain relief. A thin yellow line inside each plateau marks the boundary between its levelled plateau-like part and its steep slopes (after An- dreychouk et al., 2022). ACTA CARSOLOGICA 54/2-3 – 2025 157 in the Helenides. The magmatic rocks, mostly of Jurassic age and the Triassic-Jurassic volcano-sedimentary and the sedimentary formations are quite widespread. Among the sedimentary formations there are several large carbonate structures, the MMG being one of the largest. This structure, which has an allochthonous character (Aliaj & Bushati, 2019; Gjata & Kodra, 1999) and consists of Mesozoic Triassic-Jurassic and Cretaceous (T 3 -J 1 and J 3 -Cr 1 ) carbonate formations overthrusted over younger Paleogene flysch formations (Pg 1-2 ) of the Krasta geologi- cal zone (Liko, 1962; Gjata & Kodra, 1999). The carbon- ate rocks consist of massive limestones of high chemical purity with a total thickness of 700 to 800 m, which lie on Lower Triassic radiolarites and Jurassic effusive sedimen- tary of the basement of the massif (Figure 3). The Linos valley, located in the central part of the MMG study area, is tectonically predisposed and consists of Upper Jurassic – Lower Cretaceous series of a mélange of effusive-sedimen- tary rocks. The higher susceptibility of these sediments to erosion compared to the Upper Triassic limestones was of significant importance in the formation of the described valley, which in tectonic and geological terms divides the MMG massif into two well defined separate massifs: the western massif (Western Plateau) and the eastern massif consisting of Central and Eastern Plateaus (Andreychouk et al., 2022; Figures 2 and 3). The limestone rocks lay horizontally or sub-hori- zontally. A detailed cartography shows that the contact elevation between massive limestone and the basement rocks of the western platform (Figure 2) is an undulating surface consisting three “synclines” separated by two “an- ticlines” . This is probably the result of non-uniform over- thrusting energy of the massif, or of the different strength of the basement rocks. It seems that in the “syncline” axes the over-thrusting rocks energy has been high, or the strength of basement rocks has been low, or both as- sumptions were at work simultaneously. Concerning the eastern part of the massif the basement of the karst mas- sif deeps normally in one direction, south-north, to the Mat River. The contact between limestone and the base- ment rocks in the southern periphery of the eastern mas- sif is at the elevation about 1300-1400 m a.s.l.; and in the deeply incised Mat River Valley the carbonate rocks out- crop at elevations of about 400-500 m a.s.l. (cross-section B-B, Figure 3). 2.3 GEOMORPHOLOGY The MMG massif is very famous for its outstanding karstification. Favourable hypsometric and geomorpho- logical character, structural (high fissure permeability of limestones), lithological (chemical purity of carbonate rocks) and climatic conditions (high annual precipita- tion) favour the active development of karst throughout the MMG karst massif (Andreychouk et al., 2022; Kalin- ina, 1951; Kessler, 1958; Parise et al., 2004; Qiriazi, 2019; Doka and Qiriazi, P . 2022). In terms of geomorphology, in contrast to its geo- logical and geographical characteristics, three large units can be distinguished within it: a) the Western Plateau is developed at an elevation of about 1500-1600 m a.s.l, with its highest peak being Miceku Shenmerise reaching 1827 m a.s.l.; b) the Central Plateau is developed at elevations of about 1300-1450 m a.s.l. with some peaks reaching el- evations of about 1600 m a.s.l.; and c) the Eastern Plateau is developed at an elevation of about 1300-1600 m a.s.l with its highest peak, Shen-Noi Math, reaching 1846 m a.s.l. These units are separated by deeply incised valleys, the Linos valley separates the Western and Central Pla- teaus, and the Vali valley separates the Central Plateau from the Eastern one (Figure 3 and 4). At each plateau, two basic geomorphological environments can be distin- guished: high elevation peaks and the plateau itself, and steep peripherical slopes related to the valleys (Figure 2). The study area is characterized by high frequency and morphogenetic diversity of surface karst features both in terms of karst forms and karst terrains (Figure 4a, 4b). According to their size, they can be divided into small (microforms like karren, karren fields), medium (mesoforms like swallow holes and vertical shafts) and large (macroforms like uvalas, caves and dry valleys). The density of dolines within the MMG karst plateaus varies from 96 to about 328 per km 2 , being in average about 200 per km 2 (Andreychouk et al., 2022). Most of the dolines have circular morphology with diameters of about 15-40 m, maximum depth about 10 to more than 30 m with flattened bottom filled with residual and soil material (Figure 4b). Sometimes, from the confluence of several dolines, uvalas are formed that reach more than 300 m in width and more than 80 m in depth (Figure 4c). The closed depressions, mostly of solutional origin (Guitierrez et al., 2014) are located adjacent to each other and are separated by narrow ridges or bare rocks, form- ing a typical polygonal karst. Locally, at the bottoms of larger dolines, artificially created ponds occur, which col- lect rain and serve for watering sheep grazing on the pla- teau. One of the most important landforms of the stud- ied karst massif is the Vali dry valley about 12 km long (Figure 5a). It is formed by the Biza River, which at early Pleistocene flowed to the Mat River. As the result of the intensive lowering of the Mat River valley after Middle Pleistocene (Aliaj et al., 2018), the karst corrosion was more active than the surface erosion of the Vali River. This resulted in the formation of the deep Mat River can- yon and Biza River valley becoming a blind one; its flow disappeared underground in the Vali cave (Figure 5b), length 330 m (Denneborg, 1993). ROMEO EFTIMI, VIACHESLAV ANDREYCHOUK, PETER MALÍK, TATIANA OREHOV A, MAŁGORZATA NITA & PERIKLI QIRIAZI 158 ACTA CARSOLOGICA 54/2-3 – 2025 FACTORS INFLUENCING THE GROUNDW ATER CIRCULATION IN MALI ME GROPA KARST MASSIF, CENTRAL ALBANIA Figure 3: Hydrogeological map of the MMG karst massif and cross-sections A-A and B-B: 1 - High permeable karst aquifer, massive limestone; Low permeable rocks: 2 – Siltstone, shale (Krasta flysch); 3 - Ophiolitic conglomerate-breccias; 4 - Effusive-sedimentary rocks; 5 - Intrusive ultrabasic rocks; 6 – Groundwater level (supposed); 7 – Direction of groundwater flow; 8 – Springs and discharge in l/s; 9 – Temporary karst spring; 10 Karst groundwater drains in the river; 11 – Surface water divide; 12 – Artificial trace injection point; 13 - Limit of highly karstified area; 14 – Proved underground connection; 15 – Hydrogeological cross-section; 16 – Meteostation Selita (modified from Eftimi et al., 1985). ACTA CARSOLOGICA 54/2-3 – 2025 159 ROMEO EFTIMI, VIACHESLAV ANDREYCHOUK, PETER MALÍK, TATIANA OREHOV A, MAŁGORZATA NITA & PERIKLI QIRIAZI Figure 4: Some karst phenomena of the MMG karst massif: A Southern part of Western plateau. B Cultivated doline in Central Plateau; C Uvala, length about 300 m, in Central pla- teau (photos R. Eftimi and V. Andreychouk). Figure 5: Karst phenomenon in the border area between Central and Eastern Plateau of the MMG karst massif: A Vali dry (blind) valley: B Vali cave serves as swallow hole for small Biza River (Photo R. Eftimi). 160 ACTA CARSOLOGICA 54/2-3 – 2025 3. MATERIAL AND METHODS Due to its special natural features, the MMG karst massif has attracted the attention of specialists in various fields, like geologists, geomorphologists, environmentalists, hy- drogeologists, etc. However, a complex multidisciplinary study of this area has never been performed until now. Desio (1960) was first to describe the karst of the MMG in the well-known book “Manual di Geologia Applicata” . The geology of this massif is described in detail as part of the geological map of the area on a scale 1:50,000 (Liko, 1962) and its tectonic character is treated also by some re- gional geological studies (Xhomo et al., 2002; Aliaj at al., 2018; Liko, 1962). Karst of Albania is mainly described by geographers (Kristo 1973; Kristo et al., 1987; Qiriazi ,2019; Parise at al., 2004), who generally characterise it as a typical Mediterranean karst (Bakalowicz, 2015). The geomorphological Map of Albania on a scale 1:500,000 (Anonymous, 1992) characterises the MMG as a very intensively karstified area with innumerable sinkholes at the surface. The first important hydrogeological survey of the MMG was performed in 1950-1951 at the Selita karst spring (Figure 3) as a water supply source for the city of Tirana (Kalinina, 1951). In this study, the intake struc- ture of this spring was proposed as a long drainage gal- lery receiving groundwater flowing from the karstified limestone. During the investigation of the Selita Spring, Kalinina described also the karst of the Western plateau. She observed that the basement of the western karst plat- form of the MMG was an undulating surface, which was confirmed later also by the other specialists (Liko 1962; Pali, 1973). Another hydrogeological investigation is per- formed also at the St Maria karst spring, which in 1964 was diverted for the water supply of Tirana, also. Total supplied population by the springs Selita and St Maria is about 500,000 inhabitants. The hydrogeological map of Albania, scale 1:200,000 (Eftimi et al., 1985), was the first starting point for under- standing the hydrogeology of the MMG as a whole. To realize the map, all springs of the area have been iden- tified, measured and analysed at the Laboratory of Al- banian Hydrogeological Service (AHS). The major ion composition was determined by ion chromatography, colorimetry, and end-point titration. The water supply board of Tirana along a period of some tens of years has systematically measured the discharge of the Selita and St Maria springs, as well as has performed water chemi- cal analyses. Beside this for characterising the hydrogeol- ogy of the MMG, different investigation methods were applied such as detailed geomorphological investigations (Andreychouk et al., 2022), and an experiment with ar- tificial tracer with injection in Vali Cave swallow hole (Amataj, 2002). For determining the water balance of the MMG, beside the Turc (1954) empirical method, the recently developed software WaterbalANce (Mammoliti et al., 2021) was used. An important investigation is also performed for the assessment of the regional flow type and groundwater sensitivity to pollution of the MMG karst massif using the hydrograph analyses and hydro- chemical data of the Selita Spring (Eftimi & Malík, 2019). 4. HYDROGEOLOGY The most important hydrogeological features of MMG are shown on the 1:200,000 scale Hydrogeological Map (Figure 3). This massif consists of a karst aquifer lying mainly on impermeable effusive-sedimentary rocks with siliceous rocks. Generally, the recharge area of the karst aquifer overlaps with wide karst plateaus, while the dis- charge extends along the lower elevation outcrops of karst rocks and at deep Mati River canyon. The elevation difference between the recharge and discharge areas of the springs varies about 450 m to 600-700 m. The most common recharge process of the MMG is the areal in- filtration of precipitation directly to the carbonate rocks (autogenic, or diffuse recharge), but the allogenic re- charge is also present in one case. It happens in the Vali Cave where the small Biza River disappears (Figure 3) and flows to Mat River canyon (Eftimi, 2020; Eftimi et al., 1985). From the hydrogeological point of view, the MMG karst massif consists of two water bodies; the western one overlaps with the Western Plateau and the eastern one which comprises the Central and the Eastern Plateaus. Probably both water bodies are connected in the highest, southernmost part of Linos Valley, but it is not known how intensive this connection is in terms of groundwa- ter flow and water mass exchange. The discharge of karst water resources occurs along the periphery of the aquifer. Each of the large springs of the Western karst plateau, namely White Water, Selita and St Maria, emerges at the lowest points of three respective syncline undulations of the impermeable basement rocks. The Eastern water FACTORS INFLUENCING THE GROUNDW ATER CIRCULATION IN MALI ME GROPA KARST MASSIF, CENTRAL ALBANIA ACTA CARSOLOGICA 54/2-3 – 2025 161 body overlapping with the Central and Eastern plateaus drains in the deep Mat River canyon. The most important springs here are the Kroi Isake, Gurra Zeze and Gurra Stafaj Spring (Figure 3). 4.1 REGIME OF THE SPRINGS T able 1 summarizes the water flow data of all large springs of the MMG karst massif. For the springs of the MMG, Selita and St Maria, daily long-term discharge measure- ments are available for the first spring since 1953 and for the second spring since 1961. For the White-Water Spring exist only long-term, but non-systematic mea- surements. For the springs of the eastern water body the discharge measurements are missing. For analysing the discharge data of Selita Spring and their relation to the precipitation, the data for the period 1981-1996, which are more reliable, were used. Figure 6 shows some hydro- graphs of Selita Spring. The discharge regime of Selita Spring has two well defined periods (Figure 6A), one high flow period dur- ing October or November to the beginning of May, and one recession period usually lasting from May to the end of October or November with significant decrease of the spring discharge. Both discharge regimes are very differ- ent depending on the precipitation regime. The absolute minimum daily discharge is 215 l/s while the absolute maximum is 1200 l/s and the mean annual discharge is of 515 l/s. In Figure 6B, the mean monthly yields of Selita Spring and precipitation rates are plotted. The minimum monthly discharge of 320 l/s is measured during Septem- ber, and the maximum one of 731 l/s is measured during May. The graph in Figure 6C shows that the correlation between mean monthly yields of this spring and the re- spective values of precipitation is very weak. The regime of the mean annual discharge and the corresponding amount of precipitation is shown in Figure 6D. The mini- mum annual yield of Selita Spring of 409 l/s is registered during 1975 and largest one of 600 l/s is registered during 1970. Between the mean annual discharge and mean an- nual precipitation values there is a relatively good corre- lation, R 2 = 0.70 (Figure 6E). It has been established that the yearly recharge of the karst springs does not depend mainly on the annual precipitation but also on the annual distribution of precipitation (Kessler 1958, 1967). As established by detailed observation of the karst waters (Kessler, 1958), rainfall in autumn and partially of winter remain mainly at the channel-ways and narrow capillaries of the aeration zone, thus, in a certain way pre- paring the conditions for the development of infiltration in the first part of the next year. The amount of precipita- tion falling in the first four months of the year, preceding the development of the vegetation, and prior to the large losses due to evapotranspiration, is determinative for the karst water recharge (Kessler, 1967). The discharge of St Maria Spring is the sum of the discharge values of six intake structures, whose water is used for Tirana water supply (Table 1). It is also estab- lished that in addition to the used amount of water, about 200-300 l/s is the ungauged flow of St Maria Spring. As described above the groundwater of the Eastern water- body (central and eastern plateaus) totally drains into the Mat Canyon where recharges the springs Kroi Isake, Gurra Zeze and Gurra Stafaj (Figure 3, Table 1). Measur- ing the Mat River flow in the beginning and in the end of limestone part of the canyon, is established that the total discharge of the Eastern waterbody in summer time var- ies about 5 to 6 m 3 /s. The most important springs of the canyon are the perennial spring Kroi Isake and tempo- rary spring Gurra Zeze (Figure 7). Beside this the contri- bution of the Biza River disappearing in Vali Cave (Fig- ure 3), to the karst water of the eastern karst waterbody, according to some non-systematic measurements, varies about 100 to 1500 l/s, with a mean of about 300 l/s. ROMEO EFTIMI, VIACHESLAV ANDREYCHOUK, PETER MALÍK, TATIANA OREHOV A, MAŁGORZATA NITA & PERIKLI QIRIAZI Table 1: Some hydrogeological data of the springs of MMG karst massif. Karst massif Springs Elevation m a.s.l. Water Temp. °C Q mean l/s Q min l/s Q max l/s Investigation period Use Western White Water 1050 6.0-7.0 523 160 >2000 1966-1981 No use Selita 881 6.0-6.5 515 215 1200 1966-1981 Tirana water supply St. Maria 830 6.9-7.2 894 380 2700 1966-1981 Tirana water supply St Maria 830 6.9-7.2 ≈300 - - - Unused part of the spring Linos 1010 6.0-6.5 150 20 600 - No use Eastern Kroi Isake ≈650 7.8-8.1 ≈3.0 ≈1.5 ≈6.0 - No use Gurra Zezë ≈680 - - 0 some m 3 /s - No use Gurra Stafaj ≈720 8.3 ≈50 - - - No use Vali Cave 1300 - ≈300 100 ≈100-1500 1976-2008 Allogenic recharge 162 ACTA CARSOLOGICA 54/2-3 – 2025 FACTORS INFLUENCING THE GROUNDW ATER CIRCULATION IN MALI ME GROPA KARST MASSIF, CENTRAL ALBANIA Figure 6: Selita Spring discharge characteristics. A Daily discharges and precipitations 1980-1981; B Mean monthly discharges vs monthly precipitations; C Correlation between mean monthly discharges and precipitations; D Mean yearly discharges vs yearly precipitations; E Correlation between yearly discharges and precipitations, 1966-1981. Figure 7: Kroi Isake Spring issues in Mat River canyon (Photo: R. Eftimi). ACTA CARSOLOGICA 54/2-3 – 2025 163 The Institute of Nuclear Physics of Tirana and Hy- drogeological Service of Albanian in cooperation with Johanneum Research Institute of Graz, organised on the 15 th and 16 th of May 2002 a tracer experiment (Amataj, 2002, pers. comm.) with the injection of 4 tracers. As an example, we report on the main results for the tracer Rhodamine WT, which was injected into the swallow hole of Vali Cave at elevation 1300 m a.s.l. (Figure 3). Water samples taken in the Kroi Isake Spring and Gurra Zeza Spring located respectively at distances 10 km and 8.8 km respective resulted in the data given in Table 2. The maximal groundwater flow, which is related to the first tracer appearance results 40.7-52.0 m/h and the average velocity, which is related to the time arrival of maximal tracer concentration, results about 33.3-34.7 m/h. The values of the karst water flow velocity in MMG are comparable with the velocities measured in other karst massifs, for example, in some experiments realised in Slovenia where the results were from 25 to 165.6 m/h (Kogovšek & Petrič, 2003). 4.2 W ATER BALANCE OF MMG KARST MASSIF The most reliable method to determine the water balance of a karst aquifer is based on discharge measurements of all springs as well as in water balance calculations (Kresić & Stevanović, 2010). As for the case of the MMG massif there are relatively good data about the discharge of the springs of the Western Plateau, but for the springs of the Central and Eastern Plateaus the data are very scarce. For the estimation of the water balance of both areas are used two methods: (a) Turc method, and (b) WaterbalANce software (Mammoliti et al., 2021). Turc (1954) method The most important parameter for the estimation of the karst water resources is the rate of infiltration of the pre- cipitation in the karst aquifers. Usually in the hydrogeo- logical practice is used the concept of effective infiltration which represents that portion of precipitation, which reaches the aquifer and recharges the groundwater re- sources. The mean annual water balance of a karst massif is expressed by the following formula: P = Ie + E + F (1) Where: P – precipitation, mm; Ie – effective infiltration, mm; E – evapotranspiration, mm. If the surface flow is missing (F = 0), formula (1) is simplified to: P = Ie + E (2) Coefficient of infiltration = Infiltration / P (3) So, the estimation of the water balance of a karst aquifer often consists in the estimation of the effective infiltration, or of the evapotranspiration. The direct de- termination of this parameter through the discharge of the springs is more real, but often it is very difficult or expensive to organize. According to the Turc empirical method of the mean yearly precipitations and the mean air temperature of the recharge area of the karst massif are taken into consideration. The empiric methods are quite applicable in engineering practice (Boni et al., 1982; Bonacci & Ljubenkov, 2005). In Table 3, the results of the calcula- tion for the Western block and for the Eastern block are shown separately. WaterbalANce software method The recently developed software WaterbalANce (Mam- moliti et al., 2021) is an attractive, easy-to-use research tool for calculating monthly water balance, as demon- strated by its developers based on two case studies from Italy and Slovenia. Later, the software was successfully applied for hydrogeological studies in several regions of ROMEO EFTIMI, VIACHESLAV ANDREYCHOUK, PETER MALÍK, TATIANA OREHOV A, MAŁGORZATA NITA & PERIKLI QIRIAZI Table 2: The calculated groundwater flow velocity using the artificial tracer introduced in Vali Cave. Sampling spring Elevation m a.s.l. Air distance m Mean hydraulic gradient I Trace travel time of first appearance hours Maximum velocity m/h Trace travel time of max. concentration hours Mean groundwater flow velocity m/h Kroi Isake 680 10,000 0.062 192 52.0 288 34.7 Gurra Zeze 720 8,800 0.066 216 40.7 264 33.3 Table 3: The results of the water balance calculation of MMG karst massif applying the Turc method. Block Surface km 2 Mean elevation m a.s.l. Mean air temperature °C Mean yearly precipitation mm/year Infiltration mm/year Coefficient of infiltration % Renewable resources m 3 /s Module of underground flow l/s/km 2 Western 55 1500 6.5 2100 1630 78 2.86 52 Eastern 102 1350 8.0 1900 1230 65 4.59 45 164 ACTA CARSOLOGICA 54/2-3 – 2025 Bulgaria (Orehova et al., 2021a; 2021b; 2024). This meth- od is used for calculations of water balance of the W estern Plateau only. For this purpose, WaterbalANce software is used, which is based on the Thornthwaite & Mather (1957) method. This software provides monthly time series (in mm) for potential and actual evapotranspira- tion (PET, AET), soil moisture content (ST), and total monthly runoff (TOT RO), including monthly snowmelt runoff (SMRO). The meteorological data used for the calculations for the western waterbody (block), refer to the closest sta- tion Selita (Lat = 42º N). The study period covers several decades: 1966–1981. Monthly precipitation sums for the station Selita are available for the whole study period. As for the air temperature, only mean values averaged for each month are available, valid for the entire study peri- od. In the calculations, the average monthly air tempera- ture for the Western Plateau with mean elevation of 1500 m a.s.l. is extrapolated by the data of Selita and Lena me- teostations located accordingly at elevation 810 m a.s.l. and 1600 m a.s.l. This is based on the recommendation that air temperature in the mountainous areas of Albania decreases 0.7 °C for 100 m of elevation (Jaho et al., 1984, Kolaneci 2021). WaterbalANce software with monthly meteorological data from the Selita meteorological sta- tion is used to identify the elements of the water balance. The input data are presented in Table 4. Table 4: Input data for WaterbalANce software for Selita meteoro- logical station, period 1966–1981. Parameter Value Latitude (Lat, ºN) 42 Soil moisture storage capacity (SM, mm) 50 Runoff coefficient (beta, %) 30 Snowfall-rainfall temperature threshold (SRT, ºC) –3 Average precipitation 1966–1981 (P av , mm/year) 2106.2 1) Average air temperature 1966–1981 (Tm av , ºC) 6.5 Considering the typical shallow soils on the karst ter- rain, a low value of soil moisture storage capacity (SM = 50 mm) was set. In order to eliminate the accumulation and melting processes of the snow cover, the value of SRT is set to –3 ºC, which is lower than the lower average monthly temperature for each winter month. The outputs of the software are presented in Table 5. The coefficient of cor - relation between the simulated monthly time series of total runoff and the Selita Spring runoff is R 2 = 0.74. The results of the software application for the period 1978–1981 are presented in Figure 8, which shows the nearly synchronous behaviour of the simulated runoff and spring discharge. Table 5: Summarized output data for the period 1966–1981 for Selita meteorological station. Parameter Value Potential evapotranspiration (PET, mm/year) 533.7 Actual evapotranspiration (AET, mm/year) 473.9 Total runoff (TOT_RO, mm/year) 1600.8 Runoff modulus (M, l/s/km 2 ) 50.8 Mean soil moisture content (ST, mm) 43.0 Effective infiltration, defined as the difference (P – AET) for the annual averages, is 1632.3 mm/year and the coefficient of infiltration = 77.5% in the western plateau. The average annual discharge of the spring for the pe- riod 1966–1981 is Q = 515.3 l/s. With a runoff modulus value of M = 50.8 l/s/km 2 , the resulting spring-shed area is 10.1 km 2 . The values of the calculated parameters are practically similar with that benefited from Turc method (compare the values of Table 3 and 5). The calculated values of the coefficient of infiltra - tion and of the underground runoff modules seems to be very high, but they are comparable with the results for some karst massifs of the Mediterranean area. For the southern edge of the Skadar Lake in Montene- gro, the average effective infiltration varies from 60 to 80 % (Radulovic et al., 2012). For the Camposecco FACTORS INFLUENCING THE GROUNDW ATER CIRCULATION IN MALI ME GROPA KARST MASSIF, CENTRAL ALBANIA Table 2: The calculated groundwater flow velocity using the artificial tracer introduced in Vali Cave. Sampling spring Elevation m a.s.l. Air distance m Mean hydraulic gradient I Trace travel time of first appearance hours Maximum velocity m/h Trace travel time of max. concentration hours Mean groundwater flow velocity m/h Kroi Isake 680 10,000 0.062 192 52.0 288 34.7 Gurra Zeze 720 8,800 0.066 216 40.7 264 33.3 Figure 8: Comparison of mean monthly modelled runoff and mea- sured discharge of spring Selita. ACTA CARSOLOGICA 54/2-3 – 2025 165 Basin in Central Italia the effective infiltration is cal- culated at 68 % (Boni et al. 1982), for two karst massifs in Picentini mountains this coefficient is calculated as 66 % and 67 % (Fiorillo 2014; Fiorillo et al. 2012), and for the karst region of Gradole ranges about 35.6 % to 76.3 % (Bonacci 2001). According to Bayari et al. 2011 in southwestern coast of Turkey the effective infiltration is estimated at about 80-75 %. 5 DETERMINATION OF PHYSICAL ASPECTS OF MMG KARST AQUIFER 5.1 EV ALUATION OF THE FLOW WATER SYSTEM OF SELITA SPRINGS Karst aquifers are characterized by their high heterogeneity , created and organized by groundwater flow (Ford & Williams, 2007; Bakalowicz, 2005; Worthington & Ford, 2009; Stevanović ed., 2015). There are at least two end-member types of groundwater flow in karst aquifers: conduit flow related to integrated systems of solutionally enlarged openings or conduits, and diffuse flow related to flow through primary pore spaces or small-scale second- ary pore spaces (White, 1969). To identify the flow sys- tem, chemical and isotopic monitoring of springs is used (Krothe & Libra, 1983; Lakey & Krothe, 1996; Perrin et al., 2007). In general, greater hydrochemical variability of a spring during the hydrological year is indicative of a higher development of karstification. Spring water chemistry is not only a function of con- duit size but also a reflection of recharge type and particu- larly of the volume of allogenic recharge (Newson, 1971); however, a spring can be fed by a common diffuse type system although it shows a rather high coefficient of varia- tion. This is the case of studied springs Selita which have only autogenic recharge; the allogenic recharge is totally missing in the western karst plateau recharging this spring. Based on variation in water hardness, the springs are classified into diffuse flow and conduit flow (Shus- ter & White, 1971). Some more chemical parameters are used also to classify flow water systems of karst springs (Jacobson & Langmuir, 1974). In this study, as they are more trustful, the parameters used are water temperature, hardness, electrical conductivity, concentrations of SO 4 2- and Cl - , as well as rMg/rCa and rSO 4 /rCl ratios. Indexes of saturation with calcite (Sic) and dolomite (Sid) are used to find a correlation between chemical and physical attri- butes of karst systems (Eftimi & Malík, 2019). The coefficient of variation, CV [%], which is 100 times the standard deviation divided by the mean, is used to describe changes in water chemistry. This coefficient shows higher values for the conduit flow springs than these for diffuse flow springs. The values of coefficient of variation of selected physical and chemical parameters of the Selita Spring are presented in Table 6. Simple com- parison of data presented here with the data of already studied springs suggests that Selita Spring should be a conduit flow spring. The same conclusion can be reached when comparing the values of saturation indexes of cal- cite (Sic) and dolomite (Sid). Less saturation of the karst groundwater with respect to calcite and dolomite is typi- cal for springs with prevailing conduit flow; the opposite is evident with the increased participation of diffuse flow (Jacobson & Langmuir, 1974). The values of saturated in- dexes of calcite and dolomite for Selita Spring are -2.9 and -0.9, which are smaller than those of Blue Eye Spring, respectively +2.28 and +0.11, which is determined as a diffuse flow spring (Eftimi, 2005; Eftimi & Malík, 2019). 5.2 SENSITIVITY OF THE KARST GROUNDW ATER OF MMG TO POLLUTION The classification of karst aquifer systems with a diffuse recharge, based on the variation of hydrochemical com- ROMEO EFTIMI, VIACHESLAV ANDREYCHOUK, PETER MALÍK, TATIANA OREHOV A, MAŁGORZATA NITA & PERIKLI QIRIAZI Table 6: Coefficient of variation (CV%) of water physico-chemical parameters of Selita Spring in comparison with Blue Eye springs (Eftimi & Malík, 2019), Rock Spring (Shuster & White, 1971), Thomson Spring (Jacobson & Longmuir, 1974), Iskrets Spring (Eftimi & Benderev, 2007) and Al-Dhaher Spring (Abboud, 2016). Spring Type of flow Temperature (°C) Hardness (mev/l) Conductivity (μS/cm) SO 4 2- (mg/l) Cl- (mg/l) rCa/rMg rSO 4 /rCl Selita Conduit 11 13 8.3 28 25 22 32 Rock Conduit 26.9 26.0 23 12.7 17.7 - - Iskrets Conduit 10.3 13.6 - 43.7 24.4 - - Al-Dhaher Conduit 14.5 14.3 - 26.2 40.8 - - Thomson Diffuse 1.4 4.8 6.2 17.8 29 - - Blue Eye Diffuse 0.6 5.5 5.0 9.0 17.0 12 16 166 ACTA CARSOLOGICA 54/2-3 – 2025 ponents, becomes much more realistic if the classifica- tion is validated also by the results of hydrograph analy- sis, as is demonstrated in the following. Springs drain- ing integrated conduit systems have the potential for transmitting different type of pollutants including clastic particles (clays, silt) and sometimes coarser materials. The small-sized particles are easily mobilised by quick (storm) flow and are responsible for many karst springs becoming turbid after storm events (Drew & Hötzl, 1999; Goldscheider et al., 2010; White, 2010). This phenom- enon occurs particularly when intensive human activities are present in the recharge area. Discharge variability can be used to estimate region- al processes and hydraulic properties of aquifers. Springs with high discharge variability can indicate a high degree of groundwater transport. Discharge recession was dealt by many authors, starting with Boussinesq (1877) who was the first to mathematically describe discharge reces- sion, ending with later applications in karst hydrogeol- ogy (Kullman, 1990; Király, 2003; Kovács et al., 2005; Kresic & Bonacci, 2010; Fiorillo, 2014; Giacopetti et al., 2017). Hydrograph analysis of springs discharge data can be successfully used for identifying and separation of fast-flow and slow-flow regimes. Computer techniques of master curve construction (Gregor & Malík, 2012; 2014) can help a lot in discharge time-series analysis and subse- quent estimation of groundwater vulnerability to poten- tial pollution (Kullman, 1990; 2000; Malík & Vojtková, 2012; Malík, 2015). This method was successfully applied in the case of Selita and Blue Eye springs in Albania (Efti- mi & Malík, 2019). Selita spring discharge ranges from 215 to 1,200 l/s with the average of 515 l/s and median discharge of 480 l/s. The ratio of maximal and minimal discharge is 5.6 and the discharge standard deviation 191 l/s. The HydroOffice RC4 software tool (Gregor & Malík, 2014) was applied here to analyse recession curves for obtain- ing recession coefficients. Available discharge data were covering 21 calendar years for the period 1966 – 1986 by daily discharge averages. Time series data record of Selita Spring enabled construction of a master recession curve based on 20 in- dividual hydrograph recessional parts (Figure 9 and 10) using normal and logarithmical plots of discharge values. Two flow components were identified in the Selita Spring master recession curve; both of them were fast-flow com- ponents (Malík, 2015) described by linear equation (1) respectively (2): were Q t – discharge at time t [l/s] t – time elapsed from initial (maximal) discharge [day] Q 0x – x-th partial initial discharge [l/s]; maximal spring discharge Q 0 is equal to the sum of all partial ini- tial discharges β x – recession coefficient of the x-th linear (quick) flow component [1/d] The total volume of water discharged in pure recession of the Selita Spring, starting from 1200 l/s and finish- ing in zero discharge is 3,376,078 m 3 . Nearly one half of this volume (44 %) is discharged by the higher quick flow component with a relatively high recessional coef- ficient β 2 (0.0170 d -1 ). The remaining discharged volume (56 %) belongs to the first quick flow component with a lower recessional coefficient β 1 (0.00330 d 1 ). If not re- charged, the total spring discharge should drop down to zero in 303 days. In other words, as a result of equation (2) parameters, during this time the whole karstic aquifer should be emptied out, although being of maximal dis- charge at the beginning. The very high sensitivity degree of Selita Spring’s catchment area to potential groundwater contamina- tion is caused by the many existing possible sources of contaminant entry (karst pits, sinkholes, swallow holes) into the karstic aquifer, and the high potential for quick contamination spreading within the catchment because very limited retention and dispersion capabilities can be found. Potential pollutants can be quickly transported in high concentrations from quite distant places. The role of quick flow components, favoured also by the prevail- ing conduit groundwater flow is usually manifested in a quick increase of high pollutant concentrations in the groundwater resource, followed by their rapid removal (short duration of contamination event). The high sen- sitivity to pollution of Selita Spring was demonstrated in autumn 1975 when the spring water became turbid as a result of the soil cover removal in karst poljes in the spring recharge area when an attempt of their conver- sion to cultivated land started (Eftimi & Zojer 2015). The high sensitivity of the karst water to pollution asks for the well-organised protection policies (Ravbar & Šebela, 2015), as well as for increase the public education and awareness regarding the karst water management. FACTORS INFLUENCING THE GROUNDW ATER CIRCULATION IN MALI ME GROPA KARST MASSIF, CENTRAL ALBANIA (1) (2) ACTA CARSOLOGICA 54/2-3 – 2025 167 6. CONCLUSIONS Although the MMG karst massif it has attracted the at- tention of people and specialists due to the exceptional development of surface karst landforms and its large and high-quality groundwater resources, it has not been the subject of comprehensive study so far. This karst mas- sif as a highly heterogeneous environment can only be explained by applying and combining various methods, such as geomorphological and water balance studies, analysis of the groundwater regime and its relationship with meteorological data, assessment of groundwater quality and its variability, and the use of hydrochemistry and runoff data to determine groundwater flow patterns and the sensitivity of spring waters to pollution. Further- more, investigation becomes incomplete when individu- al research methods are applied in localized areas. In this paper, for the first time are summarized the results of the multi-method investigations of the MMG karst massif. The main findings of the paper are the following: (i) the location of karst springs is mainly controlled by the structure of the impermeable basement of the carbonate ROMEO EFTIMI, VIACHESLAV ANDREYCHOUK, PETER MALÍK, TATIANA OREHOV A, MAŁGORZATA NITA & PERIKLI QIRIAZI Figure  9:Master reces- sion curve of Selita Spring, with individual recessional parts of the hydrograph used for its construction and partial flow components: nor- mal plot. Figure  10: Master re- cession curve of Selita Spring, with individual recessional parts of the hydrograph used for its construction and partial flow components: loga- rithmical plot. 168 ACTA CARSOLOGICA 54/2-3 – 2025 FACTORS INFLUENCING THE GROUNDW ATER CIRCULATION IN MALI ME GROPA KARST MASSIF, CENTRAL ALBANIA aquifer; (ii) based on the long term and runoff data for the Selita Spring, their high variability is confirmed, as well as their correlation to precipitation is established; (iii) using the recently developed WaterbalANce soft- ware, a fairly high value of the mean effective infiltration (1632.3 mm/year) is obtained corresponding to an infil- tration coefficient of 77.5%; (iv) when performing sta- tistical processing of the hydrochemical data, it is found that the Selita Spring is a conduit-flow dominated karst spring; (v) the analysis of the master recession curve for the Selita Spring shows a predominance of fast-flowing components, which is a prerequisite for the rapid pas- sage of potential pollutants through the karst system. The high sensitivity to potential groundwater contamination of Selita Spring was confirmed when high water turbidity followed the removal of soil cover from newly cultivated karst poljes in the recharge area in 1975. Overall, there is no doubt that the hydrogeologi- cal characteristics of the MMG karst massif are in good agreement with its geomorphological features (develop- ment of karst landforms). The results of the multi-meth- od studies conducted on the MMG karst massif should be useful for future studies of the numerous carbonate karst regions in Albania. The importance of studying the groundwater resources of the MMG massif also lies in the detailed study of two large karst springs of the massif: Selita and St Maria, used for water supply of the city of Tirana, as well as a third one, Uji Bardhe, which is also planned to be used in the near future for the same pur- pose. Despite the research conducted on the MMG mas- sif, there are many phenomena that have not been dis- covered or scientifically explained. This particularly con- cerns the circulation of water and its temporal variability, as well as its relationship to the current and changing climate. Systematic interdisciplinary and detailed studies that use modern research technologies should be applied to the poorly understood processes associated with the sustainable development of this vulnerable environment. Author contributions RE: conceptualization, methodology, data analyses and writing-original draft. WA: conceptualization, writing the geomorphology and geology. PM: conceptualization, writing sensitivity of karst groundwater to pollution. TO: applying and writ- ing WaterbalANce software method for calculation of the groundwater balance, corrections of Abstract and Conclusions. MN: writing the geomorphology and some statistical calculations; PQ: writing the geology and geo- morphology. Funding The authors declare that no funds, grants, or other supports were received during the preparation of this manuscript. DECLARATIONS Conflict of interest No conflict of interest is de- clared for this article. Ethical approval All authors kept the “Ethical Re- sponsibilities of Authors” . Consent to participate All the authors gave explicit consent to participate in this study Consent to publish All the authors gave explicit consent to publish manuscript. REFERENCES Abboud, I., 2016. Describe and statistical Evaluation of Hydrochemical data of Karst phenomena in Jordan: Al-Dhaher Cave Karst. Researcher 2014, 5(3): 56- 76. https://www.sciencepub.net/researcher. Amataj, S., 2002. Tracer experiment in MMG karst mas- sif – personal communications. Institute of Nuclear Physics of Tirana. Anonymous, 1992. Geomorphologic map of Albania. Centre of Geographical Studies, Academy of Sci- ence of Albania. Printed in Topographic Institute, Tirana. Aliaj, Sh., 2012. 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