The aim of the study is to determine the origin of the high salinity groundwater of Geropotamos carbonate aquifer, located in an important touristic and agricultural area, on the central-northern coast of Crete (Greece). The main aquifer is composed by fractured and karstic carbonate rocks of Tripolis and Ionian tectonic nappes. Suggestions that Miocene Evaporites led to groundwater salinization were implied from previous studies, but they were unconfirmed. Water samples from 22 wells and 2 springs were analysed. The water temperature ranges between 18.1 and 22.9°C and the pH values ranging from 6.7 to 8.07 (slightly basic water). Cl, Ca, Na, HCO3 and SO4 concentrations are generally higher than Mg and K. The hydrogeochemical results showed different levels of mixing between a shallow end-member with bicarbonate-alkaline composition due to the leaching of carbonates rocks, and deeper fluids rich in Na and Cl. The Cl and Na contents are well correlated (r2=0.996) with an average Na/Cl ratio of 0.3, which is lower than Tyrrhenian Sea ratio (Na/Cl=0.56) and the dissolution of halite (Na/Cl=1) as well. The different Na/Cl ratio can be explained either by a depletion of Na, due to anionic exchanges processes with Ca between water and clay minerals, occurring in study area, or because of high salinity of the Cretan Sea (high Cl values). From this study we inferred that the sea water intrusion is the main contamination source to the aquifer, probably caused by increased over-pumping.

Groundwater high salinity in Geropotamos basin (Crete, Greece): sea water intrusion or Miocene Evaporites water interaction processes?

SDAO, Francesco
;
MONGELLI, Giovanni;PATERNOSTER, Michele
2009-01-01

Abstract

The aim of the study is to determine the origin of the high salinity groundwater of Geropotamos carbonate aquifer, located in an important touristic and agricultural area, on the central-northern coast of Crete (Greece). The main aquifer is composed by fractured and karstic carbonate rocks of Tripolis and Ionian tectonic nappes. Suggestions that Miocene Evaporites led to groundwater salinization were implied from previous studies, but they were unconfirmed. Water samples from 22 wells and 2 springs were analysed. The water temperature ranges between 18.1 and 22.9°C and the pH values ranging from 6.7 to 8.07 (slightly basic water). Cl, Ca, Na, HCO3 and SO4 concentrations are generally higher than Mg and K. The hydrogeochemical results showed different levels of mixing between a shallow end-member with bicarbonate-alkaline composition due to the leaching of carbonates rocks, and deeper fluids rich in Na and Cl. The Cl and Na contents are well correlated (r2=0.996) with an average Na/Cl ratio of 0.3, which is lower than Tyrrhenian Sea ratio (Na/Cl=0.56) and the dissolution of halite (Na/Cl=1) as well. The different Na/Cl ratio can be explained either by a depletion of Na, due to anionic exchanges processes with Ca between water and clay minerals, occurring in study area, or because of high salinity of the Cretan Sea (high Cl values). From this study we inferred that the sea water intrusion is the main contamination source to the aquifer, probably caused by increased over-pumping.
2009
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11563/16246
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