Mapping Groundwater Areas With Geophysical Methods

The application of using geophysical methods to mapping large aquifers has been under expanding interest<br>during the past few years in Finland. Applying conventional geophysical methods to unconventional targets has<br>given good results in terms of totally new information and even changed some old presumptions.<br>The methodology used in several glaciofluvial formations in southwestern Finland has begun with the<br>interpretation of bedrock structure by locating the fractured zones from low-altitude airborne geophysical and<br>digital elevation data. After that some gravity profile measurements are made across these fractures to estimate<br>the thickness of overburden. Refraction seismic soundings and ground penetrating radar are occasionally used<br>to ensure the bedrock topography and to help estimating in-situ densities.<br>Combining all the available material (geophysical data, information of groundwater levels) a three-dimensional<br>estimation of the area is obtained. This is used to conceive decisions of the groundwater storage and flow<br>capacity of the area surveyed. That has been one part in elaborating regional plan for eskers.<br>Most cases have been made in co-operation with the Southwest Finland Regional Environment Centre, the<br>Regional council of Southwest Finland, the Regional Council of Satakunta, Geological Survey of Finland and<br>industrial plants and communities which take their water from the eskers.