Geophysical techniques can map the underground conditions apart from boreholes. The use of these methods for hydrogeological applications is demonstrated for mapping of porous and structural aquifers, determination of groundwater quality (mineralization), assessment of hydraulic properties, determination of aquifer vulnerability and mapping of contaminated sites. Additionally, a description of geophysical techniques used for groundwater studies is given including seismics, resistivity methods, magnetics, ground penetrating radar and NMR (nuclear magnetic resonance). In this second edition new chapters on RMT (radio magnetotelluric) and on the determination of groundwater flow in monitoring wells are included.