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Evaluation of groundwater vulnerability in a Greek island using GIS-based models

Bartzas Georgios, Zacharaki Dimitra, Doula Maria, Komnitsas Konstantinos

Πλήρης Εγγραφή

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Περίληψη

The evaluation of groundwater vulnerability is a very important task, especially in sensitive areas such as islands where groundwater resources are scarce and often of poor quality. In the present study a geographic information systems based methodological approach is followed, considering three different models, namely the Generic DRASTIC, the Pesticide DRASTIC and the Susceptibility index (SI) in order to evaluate groundwater vulnerability in the island of Aegina, Greece. Seven parameters-depth to water, net recharge, aquifer media, soil media, topography, impact of vadose zone media and hydraulic conductivity of the aquifer (DRASTIC) along with land use changes-have been considered as weighted layers to enable an accurate mapping of groundwater contamination risk. The results indicate “high” to “very high” vulnerability to groundwater contamination along the north and the northwestern parts of Aegina island for both DRASTIC and SI models. These sensitive regions exhibit characteristics such as shallow depth to groundwater, extensive marine and alluvial deposits, highly permeable limestones, flat topography and intensive agricultural activities. The distribution of nitrate concentrations in groundwater in the study area indicated that both DRASTIC models are characterized by quite good to very good accuracy, while moderate correlation was noted for the SI model. Sensitivity analysis was also performed to assess the impact of DRASTIC and SI parameters and thus identify the most critical ones that require further future investigation. Aquifer media is the parameter that exhibited the highest impact on groundwater vulnerability indices followed by the impact of the topography and soil media. The methodology adopted in the present study can be used as a decision support tool to indicate which preventive or remedial measures need to be taken by local and regional authorities as well as by policy makers, in order to minimize the cost of groundwater monitoring and consequently improve groundwater quality and agricultural sustainability.

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