Hydrochemical Characteristics and Groundwater Quality in the Island of Lesvos, Greece

The hydrochemical characteristics of groundwater in the island of Lesvos, Greece, were studied
based on chemical analyses of groundwater samples collected from 30 locations covering all the
island’s major aquifers hosted in different lithological formations. The Plagioclase dissolution was
found to be responsible for the observed high concentrations of Na and Ca in the majority of volcanic
aquifers. Ultrabasic rocks enrich groundwater with magnesium while intense hydrothermal activity
and extensive alteration zones, which exist locally as a result of a recent volcanic activity, are
associated with the existence of sulphate type groundwater and acidic pH in some areas. Seawater
intrusion was found to be associated with high Cl- concentrations in three sampling locations. Based
on sodium adsorption ratio, percent sodium, and the US salinity diagrams, the vast majority of
groundwater samples were evaluated as suitable for irrigation purposes.