Xicai Pan

Continuous and simultaneous measurement of reflector depth and average soil-water content with multichannel ground-penetrating radar

Ground-penetrating radar is a fast noninvasive technique that can monitor subsurface structure and water-content distribution. To interpret traveltime information from single common-offset measurements, additional assumptions, such as constant permittivity, usually are required. We present a fast ground-penetrating-radar measurement technique using a multiple transmitter-and-receiver setup to measure simultaneously the reflector depth and average soil-water content. It can be considered a moving minicommon-midpoint measurement. For a simple analysis, we use a straightforward evaluation procedure that includes two traveltimes to the same reflector, obtained from different antenna separations. For a more accurate approach, an inverse evaluation procedure is added, using traveltimes obtained from all antenna separations at one position and its neighboring measurement locations. The evaluation of a synthetic data set with a lateral variability in reflector depth and an experimental example with a large variability in soil-water content are introduced to demonstrate the applicability for field-scale measurements. The crucial point for this application is the access to absolute traveltimes, which are difficult to determine accurately from common-offset measurements.

Thermal effects of lateral supra-permafrost water flow around a thermokarst lake on the Qinghai-Tibet Plateau

State Key Laboratory of Frozen Soils Engineering, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, China 2 Institute of Environment Physics, University of Heidelberg, Heidelberg, Germany Correspondence QihaoYu, State Key Laboratory of Frozen Soils Engineering, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, China. Email: yuqh@lzb.ac.cn

Multi-channel GPR to assess the influence of shallow structural heterogeneity on spatio-temporal variations of near-surface soil water content

Structural heterogeneity in the vadose zone can significantly influence the dynamics of surface and subsurface distribution of water. It is one important reason for the patterned crops in fields. GPR as a non-invasive tool facilitates the quick investigation of subsurface structures and associated soil water contents of agricultural lands. A field study site with patterned wheat was surveyed at 1.5 m line spacing using 400 MHz multichannel GPR. Through time-lapse snapshots of the ground with multi-channel GPR and surface TDR measurements after a heavy rainfall event, we (i) determine the subsurface 3D architecture, (ii) simultaneously measure the depth-averaged soil water content, and (iii) assess the influence of the structural heterogeneity on the surface and subsurface soil water redistribution. Through investigating the field-scale soil water dynamics, we discuss the relationship between soil architecture and the patterned crops in hydrological perspective. Results demonstrate that multi-channel GPR allows the collection of valuable information about the subsurface structure and soil water dynamics at site-specific land.