Groundwater Vulnerability Assessment In Pingtan Island

Pingtan is a water-shortage island county.Although the groundwater resources in the island are relatively abundant,they are not fully utilized.The exploitation and utilization of groundwater resources is an important way to solve the shortage of water resources,and groundwater vulnerability assessment is an important means to protect groundwater resources and prevent groundwater pollution.Therefore,the groundwater vulnerability assessment of Pingtan Island has important practical significance.Based on the data of hydrogeology,geographic information and socioeconomic of Pingtan Island,this paper evaluates groundwater vulnerability from two aspects:groundwater quality vulnerability and water quantity vulnerability by using Arcgis and overlay index method according to the DRASTIC model and the specific situation of Pingtan Island.The main achievements are as follows.:(1)Using ARCGIS and DRASTIC model to evaluate the vulnerability of groundwater quality in Pingtan Island.In order to avoid subjective influence,this paper uses analytic hierarchy process(AHP)and scoring principle to calculate the weight and score of indicators.The results are as follows:the area of negligible vulnerability area is the most extensive,accounting for about 135.87 km~2,accounting for 48.68%of total island area,the area of low vulnerability area is the smallest,accounting for 5.12%of total island area and is only 14.29 km~2;the area of extreme vulnerability is mainly located in the aeolian and marine plain accounting for about 35.37 km~2 and 12.67%of the land area;the area of high vulnerability is about 54.81 km~2,accounting for 19.64%.(2)Because DRASTIC model can not fully reflect the actual situation of Pingtan Island,article adjusts and modifies some indicators to construct DRASLI-QUE system for groundwater quality vulnerability assessment,and finally generate groundwater vulnerability zoning map through ARCGIS.The evaluation results show that the most widely distributed area is the negligible vulnerability area,accounting for 37.28%,is only 104.05 km~2,and the low vulnerability area is the smallest,accounting for only9.77%;the extreme vulnerability area mainly distributes in the plain area,the total area is about 53.93 km~2,accounting for 19.32%of the land area;the high vulnerability area is about 42.84 km~2,accounting for 15.35%.Finally,the evaluation results of DRASTIC system and DRASLI-QUE system are compared and analyzed.The distribution characteristics of groundwater vulnerability are identical,but their distribution and area are different.(3)In order to meet the development needs of Pingtan Island,this paper also evaluates the vulnerability of groundwater quantity in Pingtan Island:based on the overlapping index method,three evaluation indicators are selected to construct the ARF system.The evaluation results show that the extreme vulnerability area is located in Hilly and low mountain areas with poor recharge conditions and low groundwater resources,with an area of 134.69 km~2,and accounting for 48.25%of the land area;the high vulnerability area is about 20.33 km~2,accounting for 13.85%;the aeolian plain with abundant groundwater resources,good recharge and discharge conditions belongs to the low vulnerability area of groundwater resources,with an area of 38.65 km~2,accounting for 7.28%.The research results can be used for the development and utilization of groundwater resources and the prevention of groundwater pollution in Pingtan Island.