Water Quality Evaluation of Groundwater and Dam Reservoir Water: Application of the Water Quality Index to Study Sites in Greece

To detect the degradation of clean water, it is necessary to characterize its quality through water quality indices using seasonal water sampling and analysis. In the present study, the initialization of the monitoring by surface and dam water sampling was conducted in multiple areas of Greece, including the Eastern Thermaikos Gulf, Mouriki, and Marathonas basins, during both the dry and wet periods of 2022. The dam reservoirs were also monitored by capturing their orthomosaic mapping. The classification of the samples according to the Canadian Council of Ministers of Environment Water Quality Index (CCME WQI) showed that all dam water samples examined and Mouriki area samples have excellent water quality in terms of physical and chemical characteristics. However, some samples from the Eastern Thermaikos Gulf and Marathonas basins suffer from seawater intrusion, which is indicated by the high concentration levels of Na+ and Cl−, and anthropogenic activities shown by the elevated concentrations of NO3−. Moreover, the high concentration of As in samples from the Eastern Thermaikos Gulf is attributed to geothermal fluids. The importance of Cl−, NO3−, and As presence in water quality at the studied areas is also verified by the sensitivity analysis performed, pointing out the requirement of sustainable management.