159 General characteristics and classification of karst aquifers in Greece Обща характеристика и класификация на карстовите водоносни хоризонти в Гърция Konstantinos Voudouris, Nerantzis Kazakis Константинос Вудурис, Нерантзис Казакиc Aristotle University, Department of Geology, Laboratory of Engineering Geology & Hydrogeology, Thessaloniki, GR54124 Greece; E-mail: [email protected]Keywords: aquifers, classification, groundwater, karst, Greece. General Setting Carbonate rocks cover a large area of Greece, corre- sponding to a percentage approximately 30% of the total area (Fig. 1). The karst aquifer systems of Greece are developed in carbonate sedimentary (limestones and dolomites) and metamorphic rocks (marbles) and contribute significantly to water supply for domestic and irrigation use. Carbonate sedimentary rocks (lime- stones and dolomites) in Greece mainly date from the Triassic to the Cretaceous periods, whereas marbles have a Paleozoic–Mesozoic age. Both of them are well Fig. 1. Karst aquifer systems in Greece СПИСАНИЕ НА БЪЛГАРСКОТО ГЕОЛОГИЧЕСКО ДРУЖЕСТВО, год. 79, кн. 3, 2018, с. 159–160 REVIEW OF THE BULGARIAN GEOLOGICAL SOCIETY, vol. 79, part 3, 2018, p. 159–160 National Conference with international participation “GEOSCIENCES 2018”
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General characteristics and classification of karst aquifers in GreeceОбща характеристика и класификация на карстовите водоносни хоризонти в ГърцияKonstantinos Voudouris, Nerantzis KazakisКонстантинос Вудурис, Нерантзис Казакиc
Aristotle University, Department of Geology, Laboratory of Engineering Geology & Hydrogeology, Thessaloniki, GR54124 Greece; E-mail: [email protected]
Carbonate rocks cover a large area of Greece, corre-sponding to a percentage approximately 30% of the total area (Fig. 1). The karst aquifer systems of Greece are developed in carbonate sedimentary (limestones
and dolomites) and metamorphic rocks (marbles) and contribute significantly to water supply for domestic and irrigation use. Carbonate sedimentary rocks (lime-stones and dolomites) in Greece mainly date from the Triassic to the Cretaceous periods, whereas marbles have a Paleozoic–Mesozoic age. Both of them are well
Fig. 1. Karst aquifer systems in Greece
СПИСАНИЕ НА БЪЛГАРСКОТО ГЕОЛОГИЧЕСКО ДРУЖЕСТВО, год. 79, кн. 3, 2018, с. 159–160REVIEW OF THE BULGARIAN GEOLOGICAL SOCIETY, vol. 79, part 3, 2018, p. 159–160National Conference with international participation “GEOSCIENCES 2018”
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karstified due to intensive tectonic stress and relief, forming excellent aquifer systems with commonly high yield boreholes and large storage capacity. The hydrogeological behavior of carbonate rocks is con-trolled by tectonic deformation, which favors infiltra-tion and karstification (Kallioras, Marinos, 2015).
The karst aquifers discharge through springs or set of springs (submarine, coastal brackish, inland fresh-water, and thermal springs due to volcanic activity and tectonic structure of Greece). The freshwater springs contribute to the drinking water supplies in many cit-ies of Greece (Kavala, Drama, Korinthos, Xanthi, etc). Also, in some basins spring water covers the irrigation demands. Furthermore, karst water supports unique ecosystems, which are rich in biodiversity. In addition, karst aquifers are very vulnerable to external pollution (Kazakis et al., 2018). The karst features were deter-mined by the following three factors (Bakalowicz, 2015): 1) the Messinian salinity crisis causing karsti-fication in great depths below the present sea level, 2) the cold periods during the Quaternary that caused weathering of the epikarst, and 3) post-Miocene tec-tonics that created horst and graben structures causing sediments to fill large basins.
This review presents the general characteristics of karst aquifers focusing on hydraulic properties. In ad-dition, a total of 229 distinct karst systems codified by the Ministry of the Environment and Energy (Fig. 1) were classified according to five criteria: 1) lithology, 2) position, 3) quality status, 4) exploitation and quan-titative status, and 5) springs discharge.
Hydraulic properties – quality and quantity statusThe hydrogeological behaviour of karst aquifers is controlled by tectonic deformation and relief, which favors infiltration and karstification. Generally, the permeability of Greek karst systems is medium to high. Based on pumping test analyses it is concluded that, hydraulic parameters range within in a large scale of values: the hydraulic conductivity (k) ranges between 10−2 m/s and 10−6 m/s and the groundwater velocity in karstic aquifers ranges between 28–260 m/h with a maximum value of 880–1000 m/h. Transmissivity val-ues range between 30–300 m2/h; high values of trans-missivity are recorded in the upper of stratigraphic po-sition karstic aquifers, due to the intense karstification. Local flow direction is towards karst conduits.
The yield of boreholes drilled in karst aquifers has a wide range of values – 15 m3/h to 350 m3/h. It is pointed out that the deepest borehole in carbonate
rocks has been drilled in Crete Island at a depth of about 650 m below ground surface (Voudouris, 2003; Mandilaras et al., 2006).
Based on the classification of karstic aquifer sys-tems in Greece it is concluded that the majority of them, representing 80%, are developed within sedi-mentary rocks (limestones and dolomites), mainly in Western Greece, Epirus, Peloponnesus and Crete Island (Calaforra et al., 2004). 103 out of a total of 229 karst systems are inland (45%) and the rest coastal (55%). Only a percentage of 5% is of poor quality and recorded in coastal aquifers (mainly in islands) due to seawater intrusion processes (Na-Cl type), whereas the majority of the karst aquifers are characterized by good groundwater quality status (Ca-HCO3 type). This fact highlights the important role of karst aquifers to supply water for domestic use.
The “anthropic pressure” (abundance of popula-tion and economic activities on the karst systems, pol-lution from agriculture and wastewaters, changes of land uses) and the trend towards an overexploitation (for instance the decreasing of spring discharge with time, because of both climate and pumping) should be considered in order to adapt a rational exploitation of karst systems. So, an integrated management scheme aiming at sustainability of karst aquifer systems is of utmost importance to secure water supply in Greece.
References Bakalowicz, M. 2015. Karst and karst groundwater resources in
the Mediterranean. – Environmental Earth Sci., 74, 5–14. Calaforra, J. M., L. Ballarin, J. Gines, V. Perleros, L. Tiniakos.
2004. A proposal of classification of the coastal karst aq-uifers of the Mediterranean Sea. – In: The Main Coastal Karstic Aquifers of Southern Europe. COST Action 621, European Commission, EUR 20911.
Kallioras, A., P. Marinos 2015. Water resources assessment and management of karst aquifer systems in Greece. – Environmental Earth Sci., 74, 83–100.
Kazakis, N., K. Chalikakis, N. Mazzilli, C. Ollivier, A. Manakos, K. Voudouris. 2018. Management and research strategies of karst aquifers in Greece: Literature overview and exemplification based on hydrodynamic modelling and vulnerability assessment of a strategic karst aquifer. – Sci. of the Total Environment, 643, 592–609.
Mandilaras, D., K. Voudouris, G. Soulios. 2006. Hydraulic pa-rameters in the karstic aquifer systems of Greece. – In: e-Proceedings of International Conference “All about Karst and Water”. Vienna, 118–129.
Voudouris, K. 2003. Hydrogeological characteristics of the karst aquifers in central Crete, Greece. – In: Proc. of XXX IAHR Congress “Water Engineering and Research in a Learning Society”, Vol. B, August 24–29, Thessaloniki, 903–910.
