The lakes of Prespa and Ohrid represent a very important hydrogeological system shared between Albania, FYR of Macedonia and Greece, and are the largest tectonic lakes in Europe. Prespa Lake is about 150 m higher in elevation than Ohrid, and the twos are separated by high mountains (Mali Thate, 2,287 m, and Galičica Mt., 2,262 m a.s.l.), built up during the Pliocene-Quaternary tectonic events. These mountains mainly consist of Upper Triassic–Lower Jurassic limestones, with wide graben to the E (Prespa) and the W (Ohrid). Pliocene clays, sandstones, and conglomerates fill most of the lakes. In 2002, an artificial tracer experiment physically demonstrated the underground connection between them (Amataj et al., 2007).In the past, periodical oscillations of the level at Prespa Lake were in the 1-3 m range. After middle 1980’s, a steady decrease of water level has been recorded, producing serious disturbance to its ecological balance. Shape of Lake Prespa is quite irregular: the narrow sandy isthmus Gladno Polje separates it into Macro and Micro Prespa. In the recent past, Micro Prespa was a gulf of Macro Prespa, but then, due to erosion and sedimentation processes, the isthmus has been formed and the lakes separated (Popovska & Bonacci, 2007).In this contribution we illustrate the main karst geomorphological characters, also providing updated information on its hydrogeology. In Galičica Mt. the most important surface karst forms are the Petrinska Plateau, a 20 km2 feature developed at elevation of 1500 m a.s.l., and the Samari blind valley, about 7 km long, in the NE part at about 1300–1400 m a.s.l. At least 12 high elevation caves have been documented, the longest being Samoska Dupka with length of 279 m. Numerous small caves are also situated along the Prespa Lake coastline near the villages of Stenie and Gollomboc; the longest is Treni cave (315 m long) at the W point of MicroPrespa Lake (Trocino et al., 2010). The Zaver swallow hole is situated at the Prespa W border, near Mala Gorica, with an extensive karst cave just uphill. Other smaller swallow holes are near Gollomboc; about in the same area, several caves of limited size (up to some tens of meters) are present, too. All these elements are important to describe the Prespa Lakes area as a sector of potential interest for further karstological studies, addressed to a better comprehension of the karst phases that interested this trans-boundary sector. ReferencesAmataj S. et al., 2007, Tracer methods used to verify the hypothesis of Cvijic about the underground connection between Prespa and Ohrid lake. Environ. Geol. 51 (5), 749-753.Eftimi R., Stevanovic Z. & Stojov V., 2021, Hydrogeology of Mali Thate–Galičica karst massif related to the catastrophic decrease of the level of Lake Prespa. Environ. Earth Sci. 80, 708.Popovska & Bonacci O., 2007, Basic data on the hydrology of Lakes Ohrid and Prespa. Hydrol. Proc. 21, 658-664.Trocino A., Parise M. & Rizzi A., 2010, Ricerche speleologiche in Albania: primi dati sulle cavità nei pressi del lago di Prespa. XII Reg. Meeting Speleology “Spelaion 07”, 246-259.

There are 23 carbonate karst areas in Albania with a total area of 6440 km2, 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 km2. It is the subject of this paper. Although this massif has attracted attention due to its exceptional development of surface karst landforms (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 studies, including geomorphological characterization, analysis of long-term groundwater regime observations in relationship with meteorological data, water balance studies applying the recently 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 contamination. The results of the multi-method studies conducted on the MMG karst massif will inform future studies of the numerous 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 ecosystem, especially now that the MMG karst massif is in the spotlight for tourism development.

Carbonate rocks cover about 23% of Albania, with exploitable karst water resources estimated at 2.84 × 109 m3/year (about 65% of the total exploitable groundwater resources in the country). The Kruja tectonic zone is characterized by the presence of SE–NW-oriented carbonate structures, rich in fresh and thermal groundwaters. More than 80% of the thermal springs in Albania are present in this tectonic zone. One of its most interesting carbonate structures, with the presence of both cold and thermal waters, is the small karst structure of Makaresh, with a surface of 22 km2. The purpose of this article is to describe the hydrogeological characteristics of this massif; based on the physico-chemical characteristics, groundwaters of the study area are classified as cold waters (belonging to the local flow system) and thermal waters (originating in intermediate/deep flow systems). The former are mainly of HCO3-Ca or HCO3-Ca-Mg type (electrical conductivity 580–650 μS/cm, Temperature 13.9–16.6 °C). Thermal waters are mainly of the Cl-Na-Ca type (EC 7200–7800 μS/cm, T 18.5–22.5 °C); they are further characterized by high hydrogen sulfide concentration, up to about 350 mg/L. The presence of two groundwater types in the Makaresh massif is connected to the presence of two groundwater circulation systems. The main factors of the groundwater physico-chemical quality are the dissolution of rocks and minerals contained therein, the presence of hypogenic speleogenesis, and the mixing of the groundwater of the two systems. The hydrogeological studies proved that karst rocks contain considerable freshwater resources, partly used for water supply. Thermal waters are not currently exploited due to their temperature, but they are potentially suitable for thermal uses by drilling boreholes to a depth of about 1000 m.

The municipal water supply, related mainly to the cities of Albania, began to develop in the second half of the 19th century and very intensively after 1945. Today, the reported mean water production for the cities, on average, is about 300 l/capita/d, including drinking and industrial water supplies. The territory of Albania has an uneven distribution of very heterogeneous aquifers conditioning often the difficulty of municipal water supply solutions. In this article, are analyzed and classified the hydrogeological aspects of the water supply sources of the settlements, which are summarized in five groups: (a) wells in alluvial intergranular aquifers; (b) karst springs; (c) wells in karst aquifers; (d) springs in fissured rocks; and (e) mixed water sources. For each group of the water supply sources, the main concerns regarding the quantity and quality problems are analyzed, facilitated by the description of a variety of representative examples of different situations. Based on the gained experience, important recommendations are given for the better understanding of hydrogeological aspects of water supply systems, related to the river water recharge areas, the seawater intrusion in coastal aquifers, and the high vulnerability of karst aquifers, as well as transboundary aquifers. However, the main problem of public water supply of Albania remains the poor management of water supply systems, which is reflected in the significant water losses, as well as the low public awareness of requests for sustainable use.

The di ver sity of ground wa ter chem is try in the Peshkopi gyp sum karst area may be re lated to its set ting within the tec toni cally ac tive Korab Mas sif (Al ba nia), as shown by field tests of tem per a ture, pH, Eh and EC, and sam pling of the wa ters for chem ical anal y sis (both ma jor and trace com po nents) from cool brack ish springs and min er al ized ther mal springs. The re la tion ship be tween the chem i cal com po si tion of the spring wa ters and of the res er voir rocks was elu ci dated by anal y sis of anhydrite-gypsum rocks and experimental dissolution of an anhydrite-gypsum sample. Statistical analysis was used in the pro cess ing of hydrochemical data. Com par i son of an a lyt i cal re sults from 2019 with ear lier data in di cates compositional stabil ity of the groundwaters over time. Our re sults to gether with sta tis ti cal anal y sis of the hydrochemical data sup port an ear lier hy poth e sis of two sys tems of ground wa ter cir cu la tion within the anhydrite-gyp sum de pos its of the Peshkopi re gion. A shallow cir cu la tion sys tem in volves cold (10-14 & DEG;C), mainly brack ish SO4-Ca wa ters with very low con cen tra tions of Na+ and Cl- ions, re flect ing their for ma tion in a sul phate rock en vi ron ment that prob a bly cor re sponds spa tially with a gyp sum layer formed by hydration of anhydrite in the near-sur face zone. A deep cir cu la tion sys tem con di tioned, inter alia, by the presence of a large fault, brings to the sur face wa ter at up to 44 & DEG;C, sat u rated with H2S, min er al ized, of the SO4-Ca type with an in creased con tent of Na, K, HCO3, Cl, BO3 and SiO2. The chem i cal com po si tion of these wa ters, re gard less of the presence of large amounts of sulphates, is sig nif i cantly dif fer ent and sug gests the in flu ence of other fac tors on their for ma tion, such as slow cir cu la tion, con tact with flysch rocks in the fault zone and the mix ing of deep and near-sur face wa ters in the fi nal part of their as cent to the sur face.

The southern Albania coast, about 147 km long, represents one of the fastest growing areas of the country for tourism and local economy, resulting in serious problems concerning water supply. Due the karst nature of the territory, groundwater is the only remaining promising resource. The aim of this research is to describe the main characteristics and influencing factors on karst groundwater quantity and quality and the drainage type in the study area. In general, the area is very rich in groundwater resources; the estimated total renewable karst water resources being about 20 m(3)/s. Based on the different geological-structural conditions and the development of karst processes, their drainage occurs in different ways. Five main types of drainage can be distinguished along the Southern Albanian coast: (a) overflowing springs, (b) descending springs, (c) coastal springs, (d) submarine spring, and (e) diffuse drainage. Regarding water quality, only the overflowing springs have a good quality, due to the presence of impervious rocks isolating freshwater from the sea water. Good-quality springs represent 28% of the total discharge of karst water resources drained to the Adriatic and Ionian Seas. In addition, the situation becomes more difficult, because about 83% of the fresh quality karst water resources drain along a 1.5 km-long coastal strip located in the northernmost sector of the studied area. Beside this, the strong increase in population, particularly during the summer due tourism activities, as well as construction of new urban areas, are the main sources of likely pollution for some of the good-quality springs. The high anthropic pressure on groundwater resources increases the seawater intrusion phenomena, reducing the availability of freshwater resource and in specific areas, contributing to spring salinization.

Carbonate rocks occupy about 6490 km2 in Albania (23% of the country) and the total exploitable karst water resources are estimated in 2.84*109 m3/year (about 65% of the total exploitable groundwater resources in the country, and about 70% of those used for water supply). In addition, karst massifs are very rich in thermal waters, related to the ascending fluids which are essential for the development of hypogenic karstification in the outer Albanides. This type of karst facilitates the circulation regime of deep fluids, which are revealed at the surface through both numerous phenomena of hypogene karst and hot springs. The relatively small Kruja Tectonic Zone is characterized by the presence of SE-NW oriented carbonate structures, rich in thermal sources, and contains more than the 80% of Albania thermal springs. One of its most interesting carbonate structures, for the presence of both cold and thermal waters, is the small karst structure of Makaresh, with a surface of 22 km2. The purpose of this article is to describe the characteristics and factors that affect the quantitative and qualitative formation of cold and thermal groundwater in this massif. Based on the physico-chemical characteristics, groundwaters of the study area are classified in cold and thermal waters. The former are mainly of HCO3-Ca or HCO3-Ca-Mg type (Electrical Conductivity 580-650 μS/cm, Temperature 13.9-16.6° C). Thermal waters are mainly of the Cl-Na-Ca type (EC 7200-7800 μS/cm, T 18.5-22.5° C); further, they are characterized by high hydrogen sulphide concentration, up to about 350 mg/l. The presence of two groundwater types in the Makaresh massif is connected to the presence of two groundwater circulation systems. The main factors of the groundwater physic-chemical quality are the solution of rocks and minerals therein contained, the presence of hypogenic speleogenesis, and the mixing of the groundwater of the two systems. The hydrogeological studies proved that karst rocks contain considerable fresh water resources; the capacity of water wells used for the drinking water supply reaches up to about 50 l/s. Thermal waters are not currently exploited due to their temperature, but they are potentially suitable for thermal uses, by drilling boreholes at depth of about 1000 m.

The mid-altitude mountain massif of Mali me Gropa is located in the central part of Albania, rises to an altitude of 1500-1800 m a.s.l., is composed mostly of Mesozoic limestone, and is characterized by extensive surface karst development. The karst relief is dominated by *doline" morphology including "polygonal" karst. Detailed geomorphological analysis of the western part of the Mali me Gropa massif (so-called Western Massif) by means of GIS methods is used to determine and explain the morphometric and morphological diversity of the area's topography. Based on a homogeneity criterion, a number of geomorphological units with specific kinds of karst relief have been distinguished within the massif. The differences in karst sculpture concern the size (diameter) of dolines and depressions, their depth, shape and symmetry, orientation, density of occurrence and spatial pattern, which provide the basis for distinguishing geomorphological units. The spatial differentiation of the karst relief is explained by the influence of factors which are evolutionary (geological and geomorphological evolution of the massif), hypsometric (altitude difference of terrains) and geomorphologic-structural (inclination of the slopes and layers). The relatively poor expression of open karst conduits (i.e. caves and vertical shafts) on the surface of the massif may result from the relative immaturity of the epikarst zone, the widespread occurrence of residual cover on the plateau, and the accumulation of large amounts of clay material in dolines and depressions. Detailed hydrogeological studies show, however, high karst permeability and dominance of conduit flow. Considering the high geomorphological landscape and ecological value of the area, it should be granted the status of a nature reserve or national park. Geomorphological and karstological research within the massif should be continued as it represents a type of karst found also in other parts of Albania. This type of karst area is of great economic (groundwater reserves) and natural protection (environmental) importance.

The mid-altitude mountain massif of Mali me Gropa in the central part of Albania rises to an altitude of 1500–1800 m above sea level, is composed mostly of Mesozoic limestone. It is characterized by very extensive surface karst development dominated by dolines, distribution of which creates the polygonal pattern. This study provides a detailed field and GIS-based geomorphological analysis of the western part of Mali me Gropa massif aimed to determine and explain the morphometric and morphological diversity of the relief. Using the homogeneity criterion, a number of geomorphological units with specific varieties of karst relief have been distinguished. The differences concern the size (diameter) of the forms (dolines and depressions), their depth, shape and symmetry, orientation, the density of occurrence and the spatial pattern. The differentiation of the karst relief is explained by the influence of such factors as: evolutionary (geological and geomorphological evolution of the massif), hypsometric (altitude differentiation of terrains) and geomorphologic-structural (inclination of the slopes and layers). The relatively poor expression of open karst conduits (i.e. caves and vertical shafts) on the surface of the massif may result from relative immaturity of the epikarst zone, the widespread occurrence of residual cover on the plateau, and the accumulation of large amounts of clay material in dolines and depressions. Detailed hydrogeological studies show, however, high karst permeability and dominance of conduit flow. Geomorphological and karstological research of the massif should be continued as it represents a type of karst massif found also in other parts of Albania and the entire Mediterranean region. Karst areas of this type are of great economic (large reservoirs of good quality water) and nature protection (specific environment) importance.

The territory of Albania presents wide outcrops of soluble rocks, with typical karst land-forms and the presence of remarkable carbonate aquifers. Many karst areas are located near the coasts, which results in a variety of environmental problems, mostly related to marine intrusion. This paper focuses on the brackish springs of Albania, which exhibit temperatures approximately equal to the yearly air temperature at their location. Total dissolved solids of the springs are higher than 1000 mg/L, their waters are not drinkable, and they are rarely used for other purposes. The groundwater of the alluvial aquifers of Albania, particularly those of Pre-Adriatic Lowland, are often brackish too, but these will not be addressed here. Brackish springs of Albania are mainly of karst origin and can be classified into two groups: springs in evaporitic rock, mainly gypsum, and springs in carbonate rock. The hydro-chemical facies of the first group are usually Ca-SO4, locally with increased concentrations of Na-Cl, whereas springs belonging to the second group usually exhibit Na-Cl facies. The largest brackish springs of Albania are described in detail, including their hydro-chemical correlations.

Korça intermountain basin is the largest of its kind in Albania and from the hydrogeological point of view represents a semiclosed intermountain basin developed in Pliocene-Holocene granular unconsolidated deposits, which maximal thickness is about 300 m. The aquifer consists of intergranular gravelly to sandy layers containing artesian groundwater and the drilling wells are free flowing on most of the basin surface. The main recharge of the intergranular aquifer comes mainly from the rivers and torrents flowing from mountain gorges around the Korça Plain. The natural groundwater drainage of Korça basin is realized through the vertical leakage in the area of the former Maliq marsh. Hydrochemistry of the aquifers show the presence of four main hydrochemical facies which are related mainly to the hydrochemistry of the recharge sources and to the solution processes and ion exchange. In the central part of the basin the water supply wells of the cities Korça and Maliq are located. The natural renewable groundwater resources of the basin are relatively restricted, but the volume resources (or static water resources) are abundant (about 1.1 × 10–9 m3). The perspective of their exploitation is very important, but respecting the “basin yield” concept that is defined as the maximum rate of withdrawal that can be sustained by the hydrogeological system of groundwater basin without causing unacceptable changes to any other environmental component of the basin. To face the problems related to the intensification of the groundwater pumping systematic observations of the hydraulic reaction of the basin and of the possible groundwater quality deterioration and other negative environmental impacts must be organized. The purpose of the present study is for the first time to analyze the abundant basin wide hydrogeological data and to evaluate: (1) geometry and hydraulic parameters of the aquifers: (2) groundwater hydrodynamic conditions; (3) their chemical composition and (4) the natural groundwater resources and the possibility to intensify the groundwater pumping in close relation to the environmental impact.

Abstract The southern Albania coast, about 147 km-long, represents one of the most developing areas of the country for tourism and local economy. There are, however, serious problems as concerns water supply. Due to the karst nature of the territory, groundwater is the only remaining promising resource. The aim of this research is to describe the main characteristics and influencing factors on karst groundwater quantity and quality and the drainage type in the study area. In general, the area is very rich on groundwater resources; the estimated total renewable karst water resources are about 21.5 m3/s. Based upon the different geological-structural conditions and the development of karst processes, their drainage occurs in different ways. Five main types of drainage can be distinguished along the Southern Albanian coast: a) overflowing springs, b) descending springs, c) coastal springs, d) submarine spring, and e) diffuse drainage. As regards water quality, only the overflowing springs have a good quality, due to the presence of impervious rocks isolating freshwater from the sea water. Good-quality springs represent 28% of the total discharge of karst water resources drained to the Adriatic and Ionian Seas. In addition, the situation become more difficult because about 83% of fresh quality karst water resources drain along a 1.5 km-long coastal strip located in the northernmost sector of the studied area. Beside this, the strong increase in population, particularly during the summer due to tourism activities, as well as construction of new urban areas, are the main sources of likely pollution for some of the good-quality springs. The high anthropic pressure on groundwater resources increases the seawater intrusion phenomena, reducing the available freshwater resource and, at specific areas, contributing to spring salinization.

The lakes Ohrid and Prespa are located on the Balkan Peninsula, at the border between Albania, North Macedonia and Greece. They are separated by the high mountain chain of the Mali Thate-Galičica, which consist of highly karstified rocks, through which water from Lake Prespa drains into Lake Ohrid. This area has been a UNESCO world heritage site since 1979. A very rapid decrease of the level of the big Prespa Lake was observed during the period 1963–2020. There are different explanations and hypotheses in an attempt to explain the decrease of lake levels. These are: (a) an increase of transmissibility of the karst aquifer separating these lakes, caused by geologic–tectonic reasons and resulting in intensification of drainage; (b) the increased use of lake water by the local population for agricultural, industrial and other purposes, and (c) the effects of recent climate changes. The paper presents information about the hydrogeology of the region for the purpose of better understanding the formation of the karst water resources and the characteristics of their circulation. Analysing a large number of investigations which unevenly covering the investigated area, the authors concluded that the current catastrophic decrease of the level of Lake Prespa is largely the result of climate changes that have occurred in the last 60 years, as well as the non-effective management of the water resources. The severity of the problem, reflected directly in the well-being of the local population, requires cooperation of the scientists of the three countries in question with respect to the realisation of the goal of the investigation and the protection of water resources of Lake Prespa.

The Dumre area, located in Central Albania, is distinguished by a landscape whose main features consist of low altitude, mosaic and irregular relief, and the presence of a large number of depressions with lakes. These features result from karst development related to the presence of a tectonically affected dome of Triassic evaporite rocks, mainly gypsum. Gypsum karstification has operated since the Pliocene, and the present-day geomorphological appearance of the area indicates an advanced, mature stage of karst development. Signs of this maturity include the widespread occurrence of large depressions, many of which are water-filled, forming lakes, the occasional presence of gypsum hills in the form of monadnocks,a thick " coating" of residual sediments largely isolating the karstic gypsum substrate from pre cipitation and surface wa ters, and the frag mentary pattern of a degraded river network. The karst character of the relief is largely "camou flaged" by clastic terrigenous and residual deposits of con siderable thickness which cover the gypsum and form a caprock. At the present stage, the caprock is being strongly reshaped and eroded. Chemi cal analyses show a mean dissolved gypsum content of 1.9 g/l and mean dissolved NaCl content of 0.4 g/l. The mean flow rate of subaqueous springs is calculated as 1.84 m3/s. The density of gypsum is 2.3, and that of rock salt is 2.17, thus the total volume of gypsum dissolved each year is 47,420 m3 and of rock salt 10,680 m3, making a total volume of dissolved material re leased by the subaqueous springs in one year of 58,100 m3. This cor responds to a cubic void of side length 38.7 m.

Karst terrains cover some 30% of the Western Balkans, where rich karst aquifers represent the main source of potable water supply and ensure the development of local economies and tourism. In this “classical karst” region, there are also numerous sites or areas under different forms of protection—from those that are included in the UNESCO World Heritage list to natural monuments and landscapes that are protected by national legislation. In and around them are specific representatives of flora and fauna that largely include endemic species. Although the area is relatively rich in surface and groundwater resources, demand for water is permanently increasing as a result of tourism expansion, intensive agriculture and urbanisation especially along the Adriatic Coast. Improper solid waste management and lack of wastewater treatment plants are the main threats to the quality of water and biodiversity. Establishing a proper balance between the extraction of water and its provision to dependant eco-systems is one of the main challenges, and appropriate requests have been included in many recently prepared River Basin Management Plans of concerned countries. Based on collected and evaluated data from 26 selected protected areas and sites located in 6 countries of the region, this study evaluates the situation and pressures on water quantity and quality on existing ecosystems. Some experiences from current legislation imposed in the study area enable to distinguish two main groups of pressure on water quantity and quality: natural (intrinsic) and anthropogenic, each with the three levels of pressure: low, medium and high. The high pressure from water abstraction has been established at six studied protected sites, while high pressure on water quality resulting from human activity is present at nine of them. There is also a discussion about possible measures that could enable further sustainable development of the aquifer systems, and some measures to protect the local ecosystems.

The karst covers some 30% of the territory of former Yugoslavia and similarly Western Balkans countries and represent fully contrasted terrain. On one side there are dry hilly mountainous terrains with deep groundwater table and terrestrial ecosystems adapted to these circumstances while on another, in the foothills and along erosional bases are often located strong karst springs which originate many perennials and sinking rivers or recharge the lakes. These rich karst aquifers are the main source for water supply of local inhabitants and aquatic ecosystems. In this “classical karst” region where the Dinaric Mountains arch represents dominant geological structure there are numerous landscapes, features and biotopes under different kinds of protection, from those included in UNESCO’s World Heritage list to natural monuments and areas protected by national legislatives. They are inhabited by specific biocenoses including underground endemic species such as famous olm Proteus anguinus. Although rich in surface and groundwater resources in comparison to rest of Europe water demands are permanently increasing as result of tourism expansion, intensive agriculture and urbanization. This is why during recession and drought periods lack of sufficient water may cause restrictions in potable water supply along with water shortage for dependent ecosystems. Establish a proper balance between abstraction for domestic water supply and water provision to dependent ecosystems is one of the main challenges and requests which had been included in several recently prepared River Basin Management Plans of concerned countries. In certain areas engineering solutions and interventions may improve water situation and ensure more water available to the consumers. Improper solid waste management and lack of wastewater treatment plants represent other main threats to the quality of spring water.

Albania is situated in the western part of Balkan Peninsula, on the eastern coast of the Adriatic and the Ionian Sea, which is one of the most water−rich regions of the world. The karst landscape in Albania covers about 2750 km2 consisting of nearly 24% of the countries territory. Karstic aquifers are the richest in the country. The total renewable karst water resources represent about 80% of the groundwater resources of Albania and nearly 80% of the population of the cities, including the capital Tirana, are supplied by karst water, and important resource is used for the production of the electricity. The sustainable management of karst water resource is difficult due to the high heterogeneity of karst aquifers in terms of type and development of hydraulic porosity, flow velocities, hydraulic head, recharge type and quantity, karst water quality, as well as to the high vulnerability to the human impact.

The assessment of groundwater vulnerability/sensitivity to pollution in karstic aquifers usually concentrates on recognition of fast-flow (conduit flow) and slow-flow (diffuse flow) components or intermediate regimes and their ratio in the total discharged volume. Analysis of master recession curves and correlation between physical characteristics of springs and temporal variations in spring water chemistry were applied to two major karst springs of Albania: Selita Spring (mean discharge 510 L s−1), exploited for Tirana water supply, and Blue Eye Spring (mean discharge 18,182 L s−1), used for electric power generation. These springs are recharged by precipitation in two very different karst areas with respect to their karstification degree, which influences also groundwater circulation patterns within karstic aquifers. Different regional groundwater flow types are subsequently reflected in the different spring hydrographs and in the temporal hydrochemical variations. Based on the spring master recession curves, Selita Spring is characterised as a conduit spring where the fast-flow component represents the majority of groundwater flow, and its catchment area should be linked with a high degree of sensitivity to pollution. On the other hand, in the discharge regime of Blue Eye Spring, the slow-flow component dominates, and although having a discharge of one order of magnitude bigger, this is a diffuse-flow spring and its catchment area should have lower sensitivity to potential pollution. The same results were also confirmed by statistical treatment of the temporal variations in spring water chemistry and evidence of surface karst phenomena in their recharge areas.