Identification Of Saltwater Intrusions And Coastal Aquifers Using The Bgr Helicopter-Borne Geophysical System

As part of a research programme, a helicopter-borne survey was conducted by the Federal<br>Institute for Geosciences and Natural Resources (BGR) of Germany covering the Coastal Aquifer Test<br>Field situated in NW-Germany between the estuaries of the Elbe and Weser rivers into the North Sea.<br>Electromagnetic data were collected in five frequencies and inverted to apparent resistivity/centroid<br>depth data sets for each frequency. These served as starting models to determine 1-D stratified n-layer<br>models for each data point using a Marquardt inversion. Results are presented as resistivity maps for<br>selected depth levels and as vertical sections depicting the variations of the true resistivity with depth<br>and distance along each flight line. Saltwater intrusions, seaside and inland freshwater aquifers and<br>glacial meltwater channels have been clearly identified and mapped. Airborne geophysics have proven a<br>fast and cost-effective tool for natural resource management.