In most of the 20th century the geo-electrical methods were primarily used for groundwater exploration and the application of the methods were normally followed by a borehole, and a moment of truth. In this process the use of DC (direct current) soundings have been developed to a high grade of excellence. In the last 25 years the geo-electrical methods are more used in connection with groundwater protection and planning, and new methods, as transient electromagnetic (TEM) soundings, have been developed that provide more measurements per hour. In Denmark this change is very explicit, and a paper has – compared results of TEM based mapping with results from wells in a test area north of Aarhus – and stated that: “it is time to do away with the old way of using geophysics”. The present paper tests this statement and concludes that critical boreholes have been overlooked in the analysis. The test area was earlier mapped by DC-soundings, so it is possible to test the methods against each other. It is concluded that well performed DC-soundings with a Schlumberger configuration still provide the best base for hydrogeological mapping.
- Geophysical Methods, Groundwater Exploration, Groundwater Protection, Denmark