Groundwater vulnerability assessment of a coastal aquifer system at River Nestos eastern Delta, Greece

Processes such as urbanization, agricultural development and industrialization have led to increasing demand of groundwater resources resulting in pollution threats to groundwater in different ways, either as contaminant loads on the ground surface, or as seawater intrusion due to overexploitation of wells in the coastal zone. Two groundwater vulnerability indices are applied in this paper to assess the potential risk of groundwater contamination in the eastern delta of Nestos River, Greece. DRASTIC model is used in this paper to evaluate the groundwater vulnerability of the area with focus on agrochemical contaminants, more especially on nitrate pollution, since the region is highly cultivated. Additionally, GALDIT index is also applied to assess the vulnerability of the freshwater aquifer to seawater intrusion, as the extensive pumping of the coastal wells has led to this phenomenon. The vulnerability assessment showed that the study area experiences low to moderate groundwater vulnerability to agrochemical contaminants, as well as moderate to high vulnerability to seawater intrusion. The use of GIS for both vulnerability indices was found effective for the evaluation of each method in comparison to real field data.