Current conditions of saltwater intrusion in the coastal Rhodope aquifer system, northeastern Greece

The geological, hydrogeological and hydrochemical regimes of the coastal Rhodope aquifer system, northeastern Greece, are described. The aquifer system includes two aquifers within coarse grained alluvial sediments. Both vertical and lateral saline water intrusion occurs, usually caused by over pumping. Water has been pumped from the aquifer system at an ever-increasing rate for many years. Water samples for chemical analyses were obtained from 36 productive wells and from 5 research wells at several depths to cover the entire study area. The EC and chloride concentration distribution clearly illustrate the large extent of saline water intrusion in the aquifer system of the study area. Although the ionic content of groundwater of the study area is highly variable, the dominant anions are HCO3- and Cl- and the dominant cations are Na+ and Ca2+. Water in the saline parts of the confined aquifer is generally of the Ca2+-Cl- type. Evidence of cation exchange and reverse cation reaction between fresh and saltwater in the Rhodope aquifer system are reflected in the Piper diagram and the expanded Durov hydrochemical diagram, respectively, both for productive and research wells. The results of this study show that the development of a strategy for managing the aquifer system is vitally necessary.