Groundwater Vulnerability Assessment of Pingtan Island in Fuzhou City, China, Based on DRASLI-QUE

Based on the DRASTIC model [A model for groundwater vulnerability assessment including seven indexes: depth to groundwater (D), net recharge (R), aquifer medium (A), soil type (S), topography (T), impact of the vadose zone (I), and hydraulic conductivity (C)], aiming at the impact of geological and geomorphological conditions and the human activity influence in Pingtan Island, four indexes, namely landform type ($L$), groundwater quality ($Q$), land-use type ($U$), and groundwater exploitation modulus ($E$), were added, and two indexes, namely hydraulic conductivity ($C$) and topography ($T$), were removed, and the groundwater vulnerability assessment model DRASLI-QUE [A model for groundwater vulnerability assessment including nine indexes: depth to groundwater (D), net recharge (R), aquifer type (A), soil type (S), landform type (L), impact of the vadose zone (I), groundwater quality (Q), land-use type (U), and groundwater exploitation modulus (E)] was established. The model was validated, and the conclusions were as follows. First, DRASLI-QUE model assessment results showed that areas of very low, low, and moderate vulnerability account for a large proportion of Pingtan Island. The very-high-vulnerability areas are mainly distributed in river basins and aeolian plain areas, and the high-vulnerability areas are mainly distributed in marine plain areas. Second, the water quality of drilling sites was selected to verify the assessment results, and the results showed that the groundwater vulnerability obtained by the DRASLI-QUE model was highly consistent with the actual water quality. Therefore, compared with the DRASTIC model, the DRASLI-QUE model was more suitable for the actual situation of Pingtan Island. Finally, compared with the DRASTIC model, the DRASLI-QUE model focuses on the process of surface pollutants entering the aquifer and water quality and the impact of human activities on water vulnerability. Therefore, in the evaluation results, the vulnerability level of aeolian plain areas with large amounts of farmland was raised from high to very high. In some mountain areas, due to heavy groundwater exploitation and poor groundwater quality, the vulnerability level was upgraded from very low vulnerability to low vulnerability.