Moisture assessment with small-scale geophysics - the Interurban project
M. Müller, O. Mohnke, J. Schmalholz and U. Yaramanci
Journal name: Near Surface Geophysics
Issue: Vol 1, No 4, November 2003 pp. 173 - 181
Info: Article, PDF ( 5.62Mb )
Price: € 30
Urban soils are subject to strong variations in environmental conditions, such as water flow, solute transport and heat budget. The INTERURBAN research project has been set up to investigate the dynamics of water and solutes at urban locations with particular attention to spatial heterogeneity, organic soil substance, and soil-biological transformation processes inthe unsaturated zone. The objectives of INTERURBAN also define the tasks for geophysics: the development of non-invasive procedures to map water distribution, water dynamics and important structural parameters at small scales. This paper focuses on the development of a geophysical methodology as a tool for soil research. Approaches to adapting geophysical methods for particular objectives in the framework of the project have been successful. Soil moisture could be derived from ground-penetrating radar (GPR) in combination with time-domain reflectometry (TDR), high-resolution direct-current geoelectrics (DC on a dmscale) could be realized and a newly developed direct-push spectral induced-polarization (SIP) probe delivered high-quality data. The resistivities and phases derived from the direct-push SIP data correlate very well with the water content and decay times derived from nuclear magnetic resonance (NMR) measurements performed in the laboratory on a corefrom the same site. For DC geoelectrics and SIP, the layout of the sensors was a customized high-resolution multi-electrode configuration (a comb of electrodes with an electrodespacing of 5 cm) and the influence of the short electrode spacing (line electrode) was corrected for. For GPR metal plates were buried at a known depth to allow monitoring of the traveltime by means of water content. Furthermore, the ground wave has been used to determine the shallow water content which correlates well with TDR measurements. For surface NMR (SNMR),smaller loops and excitation intensities were used to enhance there solution of the method for shallow depths.