Geoinformatik / GIS

Search for groundwater

Among all basic services, drinking water is the most important. Satellite imagery can help to locate groundwater resources in many ways. In crystalline rocks, lineaments and other large scaled structures are indicators for subsurface aquifers. These lineaments can be retrieved from digital elevation models of high resolution (TanDEM-X) or imaging systems. While optical data often offers limited potential in arid regions, wavelengths of SAR satellites are able to penetrate dry surfaces and give information on variations in grain size, water content and chemical composition of the surface rocks. The image below shows a multi-sensor composite of SAR data around the city of Kidal, Eastern Mali. Buried river channels which are covered by loose sands (red) can now clearly be identified, as well as granitic massifs (blue). In the vicinity of the city of Kidal, lineaments and ridges light lines are enhanced on green and yellow background.

This information assist the site selection of boreholes and can be used for recommendations for new drillings.

Digital Elevation Models

Radar interferometry is used to retrieve high-resolution elevation information out of image pairs. Below, an example is given for the area around Koudougou, Burkina Faso. While freely available DEMs (SRTM 1ArcSecond, ALOS World DEM, ASTER GDEM) are mostly limited to a spatial resolution of 30 meters, the TanDEM-X mission was used to globally map the earth's surface at a resolution of 12.5 meters. It reveals detailled description of topography and improves the quality of hydrologic modelling of surface flow and discharge processes.