Delta Life 8

22 Electromagnetic receiver, records minimal fluctuations in resistance in the electromagnetic field. Stabiliser ensures stable flight in a straight line. Electromag- netic trans- mitter sends a wave into the ground. The container with the measuring equipment inside. Special ropes that, depending on the wind and the flight height, keep the 'cigar' in a stable position. Marios Karaoulis processes data from the 'cigar' of the German research firm BGR. T he salinisation of groundwater is a problem in coastal areas for farmers and managers of drinking water so there is an urgent need to map out the locations of fresh water and salt water. The 'cigar' from the German research firm BGR uses an electromagnetic field to conduct an aerial survey that penetrates 160 metres below the ground. The resistance of salt water is ten times less than that of fresh water. This survey technology was already available but Deltares has been involved in the development of an approach to create a 3D picture of the results. 'That's quite a step forward', says geophysicist Marios Karaoulis, who puts the results of the measurements into models to chart the groundwater. 'We have even found fresh water under salt water. There is no way we would have known that with­ out this technology.' The device is affectionately known as the 'bird', the 'cigar' and the 'torpedo'. The shape is, of course, designed to maximise stability during flight. Depending on the wind and the altitude of the flight, it is important to determine precisely on each occasion the position of the cigar below the helicopter. A mobile ground station (which cannot be seen in the photograph) makes additional checks on the reliability of the data. LOOKING FOR FRESHWATER TESTING GROUND