HR: 1340h
AN: H23A-1005    [Abstracts]
TI: More Accurate Estimation of Water Table Elevation in the Unconsolidated Sediment Aquifer Using Ground Penetrating Radar
AU: * Kim, C
EM: kyungsok@kigam.re.kr
AF: Korea Institute of Geoscience and Mineral Resources, Gwahang-no 92, Yuseong-gu, Daejeon, 305-350, Korea, Republic of
AU: Son, J
EM: jsson@kigam.re.kr
AF: Korea Institute of Geoscience and Mineral Resources, Gwahang-no 92, Yuseong-gu, Daejeon, 305-350, Korea, Republic of
AU: Ko, K
EM: kyungsok@kigam.re.kr
AF: Korea Institute of Geoscience and Mineral Resources, Gwahang-no 92, Yuseong-gu, Daejeon, 305-350, Korea, Republic of
AU: Kim, J
EM: jungho@kigam.re.kr
AF: Korea Institute of Geoscience and Mineral Resources, Gwahang-no 92, Yuseong-gu, Daejeon, 305-350, Korea, Republic of
AB: More than two decades, Ground Penetrating Radar (GPR) as a non-invasive sounding technique has been used to detect and map the water table in the unconfined sediment aquifer under the favorable conditions such as in the coarse grained sediment aquifer. Therefore, more accurate estimation of the water table elevation (or depth) using GPR has become a great environmental concern to geophysicists. In general, the vadose zone can be conceptualized as three zones including: (1) a pendular zone with a residual saturation, (2) a transition (or funicular) zone, and (3) capillary fringe (tension-saturated zone) from the ground surface to the water table. In the transition zone, water content increases gradually until it reaches to the tension-saturation (close to 100 percent) at the height of air-entry head. The thicknesses of the transition zone and capillary fringe are greatly controlled by the soil texture in the subsurface. It is known that the GPR reflection associated with water table is from the top of the capillary fringe above the water table. In this study, both numerical and physical model experiments with GPR frequencies of 500 and 1,000 MHz antenna were conducted to more accurately estimate the water table elevation by simulating the vadose zone with various thickness of the transition zone above the capillary fringe in the different sediment aquifers. In addition, the heights of the capillary fringe and transition zone in the different sediments were measured in the laboratory. The results of the experiments demonstrate that the GPR reflection associated with the water table actually occurs at the uppermost part of the transition zone, not the top of the capillary fringe above the water table. From the study results, the water table elevation can be obtained by subtracting the estimates of the heights of both capillary fringe and transition zone from the GPR-detected water table elevation. Therefore, the main sources affecting the estimation error in the water table elevation can be reduced by considering the presence of the transition zone and capillary fringe above the water table in the sediment aquifer.
DE: 1719 Hydrology
DE: 1829 Groundwater hydrology
DE: 1835 Hydrogeophysics
SC: Hydrology [H]
MN: 2007 Fall Meeting