『Abstract
　Groundwater quality is determined by a variety of factors. Petrographic properties of the rocks in the vadose and in the groundwater saturated zones as well as the regional hydrological and hydrodynamic conditions are regarded as its major natural influencing factors together with groundwater's initial composition. For an assessment of major groundwater composition on a continental scale, the complexity of individual aquifers needs to be organized into simplified patterns. For this purpose, European scientists, among them representatives from several European national geological surveys, jointly defined a harmonized European aquifer typology, which includes the major classes of aquifers showing comparable petrographic properties. This process has led to the development of the European aquifer typology map presented in this paper. similar groundwater compositions are expected for the various classes in comparable hydrodynamic and hydrologic conditions. Application of the aquifer typology with regard to the intercomparison of hydrochemical data sets across Europe for several aquifer types clearly points out that typical groundwater compositions can be distinguished for the various aquifer types. In the future this typology may serve as a basis for referencing hydrogeochemical groundwater composition on a European scale.

Keywords: European aquifer typology; Hydrogeochemical properties; Chemical state of groundwater; Groundwater composition; European groundwater directive』

Introduction
Factors influencing groundwater quality
Aquifer mapping of Europe
Objectives and procedure of aquifer typology derivation
Examples of groundwater composition in the same aquifer types throughout Europe
　Sands and gravels
　Limestones and crystalline rocks
Conclusion
Acknowledgments
References