Model-based assessment of groundwater vulnerability for the Dalyan Region of southwestern Mediterranean Turkey

The Dalyan Region that drains into a complex lagoon system is located on the Mediterranean Sea coast of southwest Turkey. There are no large streams in the area, indicating that a considerable amount of freshwater draining into the lagoon is expected to be based on groundwater inflows and that groundwater quality is an important issue for the lagoon ecosystem. Since the lagoon and its watershed are within an environmental special protection area, planning preventive and mitigative measures toward water quantity and quality, including groundwater, is crucial. Since an important step in such a study is the generation of vulnerability map of groundwater pollution, this study aims at the generation of an intrinsic groundwater vulnerability map and its assessment for the first time in the study area based on the DRASTIC method. Since the DRASTIC method requires recharge rates for the calculation of groundwater pollution potential index, these were obtained from a previous modeling study conducted in the same area, where SWAT model was used. The intrinsic vulnerability maps generated were overlaid with current land-use maps to evaluate actual groundwater pollution risk. Our analyses showed that 46% of the study area is under the high risk of groundwater pollution, where 62% of the vulnerable high-risk area is agricultural land.