『Abstract
　The assessment of groundwater vulnerability to pollution aims at highlighting areas at a high risk of being polluted. This study presents a methodology, to estimate the risk of an aquifer to be polluted from concentrated and/or dispersed sources, which applies an overlay and index method involving several parameters. The parameters are categorized into three factor groups: factor group 1 includes parameters relevant to the internal aquifer system's properties, thus determining the intrinsic aquifer vulnerability to pollution; factor group 2 comprises parameters relevant to the external stresses to the system, such as human activities and rainfall effects; factor group 3 incorporates specific geological settings, such as the presence of geothermal fields or salt intrusion zones, into the computation process. Geographical information systems have been used for data acquisition and processing, coupled with a multicriteria evaluation technique enhanced with fuzzy factor standardization. Moreover, besides assigning weights to factors, a second set of weights, i.e., order weights, has been applied to factors on a pixel by pixel basis, thus allowing control of the level of risk in the vulnerability determination and the enhancement of local site characteristics. Individual analysis of each factor group resulted in three intermediate groundwater vulnerability to pollution maps, which were combined in order to produce the final composite groundwater vulnerability map for the study area. The method has been applied in the region of Eastern Macedonia and Thrace (Northern Greece), an area of approximately 14,000 km². The methodology has been tested and calibrated against the measured nitrate concentration in wells, in the northwest part of the study area, providing results related to the aggregation and weighting procedure.

Keywords: Groundwater vulnerability; Fuzzy logic; Multicriteria evaluation; Geographic information systems』

Introduction
Methodology description
Methodology application
　Factor group 1: assignment of intrinsic aquifer vulnerability
　　Factor 1: aquifer type
　　Factor 2: hydraulic conductivity
　　Factor 3: depth to water table
　Factor group 2: assignment of aquifer vulnerability related to external forces
　　Factor 4: surface runoff
　　Factor 5: non-concentrated land uses
　　Factor 6: proximity to concentrated land uses
　　Factor 7: proximity to major rivers
　　Factor 8: proximity to residential areas
　　Factor 9: areas protected by national law or international environmental treaties
　　Factor 10: proximity to highways and railways
　Factor group 3: assignment of aquifer vulnerability related to the presence of local geological conditions
　　Factor 11: presence of geothermal fields
　　Factor 12: presence of salt water intrusion zones
Aggregation procedure and results
　Weighting and aggregating factor group 1
　Weighting and aggregating factor group 2
　Weighting and aggregating factor group 3
　Weighting and aggregating intermediate results
Discussion
Conclusions
Acknowledgements
References

• DRASTIC system (Aller et al., 1987)
• GOD system (Foster, 1987)
• AVI rating system (Van Stempvoort et al., 1993)
• SINTACS method (Civita, 1994)
• ISIS method (Civita and De Regibus, 1995)
• German method (Von Hoyer and Sofnerr, 1998)
• EPIK (Doerfliger et al., 1999)
• Irish perspective (Daly et al., 2002)
• 上記の帯水層脆弱性評価法の比較
  Gogu,R.C. and Dassargues,A.(2000）: Current trends and further challenges in groundwater vulnerability assessment using overlay and index methods. Environ. Geol., 39, 549-559.
  Gogu,R.C., Hallet,V. and Dassargues,A.(2003): Comparison of aquifer vulnerability assessment techniques. Application to Neblon（eの頭に´） river basin (Belgium). Environ. Geol., 44, 881-892.