Geoscience Reference
In-Depth Information
23 GPR Surveys across a
Prototype Surface Barrier
to Determine Temporal
and Spatial Variations in
Soil Moisture Content
William P. Clement and Andy L. Ward
ContentS
23.1 Introduction ......................................................................................................................... 305
23.2 Methods (GPR Surveys) ...................................................................................................... 306
23.3 Data and Analysis ............................................................................................................... 309
23.3.1 Finding the Optimal Offset ................................................................................... 310
23.3.2 Wide-Offset Surveys ............................................................................................. 310
23.4 Conclusions ......................................................................................................................... 314
23.5 Acknowledgments ............................................................................................................... 314
References ...................................................................................................................................... 315
23.1 IntRodUCtIon
Measurement of the electromagnetic (EM) properties of the subsurface can provide estimates of
important hydrological parameters such as porosity in the saturated zone and soil moisture content
in the vadose zone. Importantly, EM methods can be deployed across the ground surface and are thus
a noninvasive method to sample the subsurface. Ground-penetrating radar (GPR), a high-frequency
EM method, acquires data quickly and at high spatial densities to provide a detailed distribution of
the desired property.
Many experiments have used GPR to test the validity of using radar energy to map soil mois-
ture content (Berktold et al., 1998; Chanzy et al., 1996; Charlton, 2000; Du and Rummel, 1994:,
Greaves et al., 1996; Huisman et al., 2001; Lesmes et al., 1999; van Overmeeren et al., 1997; Weiler
et al., 1998). Most of these experiments were small, test-of-concept surveys. Grote et al. (2002) used
GPR to monitor the volumetric water content in soils for a highway construction and maintenance
application. Grote et al. (2003) and Hubbard et al. (2002) have recently used GPR to map soil mois-
ture content across a vineyard. GPR measurements are converted to soil moisture content and have
shown promising results for measuring soil moisture content.
We present data collected at the U.S. Department of Energy's Hanford Site in southeastern
Washington where a study was conducted to assess the viability of GPR to monitor changes in the
soil moisture distribution in the engineered barrier. At Hanford, surface barriers are being tested
305
 
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