Geophysical techniques can map the underground conditions apart from boreholes. The use of these methods for hydrogeological applications is demonstrated for mapping of porous aquifers, mapping of structural aquifers, determintation of groundwater quality (mineralization), geophysical assessment of hydraulic properties, determination of aquifer vulnerability, and mapping of comtaminated sites. Additionally, a description of applied geophysical techniques used for groundwater studies is given including seismics, resistivity methods, magnetics, and ground penetrating radar. Even advanced techniques like NMR (nuclear magnetic resonance) are presented.