Assessment of Groundwater Salinization Using Combined Hydrogeochemical Tools: The Case of Rhodope Aquifer (NE Greece)

The Rhodope coastal area (NE Greece) is an intensively cultivated agricultural region with profound signatures of water quality deterioration because of elevated salinity. Within the MEDSAL Project ( www.medsal.eu ) activities, a thorough study of hydrogeochemical characteristics was performed to assess the extent of groundwater salinization and identify its dynamics. A combined suite of hydrogeochemical tools was applied to the data of forty-six (46) groundwater samples collected in June 2020. Calculating salinization facies (SFs) allowed classifying samples according to their chloride content. The salinization phenomenon is evident since nearly 30% of groundwater samples result in brackish (B) or brackish saline (Bs) with Cl− > 1000 mg/L). Most saline samples (B and Bs) are distributed in two areas close to the coastline. Nevertheless, seawater intrusion is not the dominant salinization cause, as the effect from an additional diluted brine is profound. The fresh (F) and fresh-brackish (Fb) waters are located further inland than the B sample. However, they do not show any definite spatial pattern distribution. Considering the hydrogeological regime of the area, the F samples are likely to be significantly affected by the deeper (confined) aquifer layer of better qualitative conditions. Based on a series of binary plots of major elements versus Cl−, we conclude that salinization may result from one single source or a combination of more sources from place to place. According to previous reports and surveys, additional cascading sources may include trapped saline lenses and irrigation water return.