TY - JOUR
T1 - Using the resistivity imaging method to monitor the dynamic effects on the vadose zone during pumping tests at the pengtsuo site in pingtung, Taiwan
AU - Chang, Ping Yu
AU - Hsu, Shao Yiu
AU - Chang, Liang Cheng
AU - Chen, Wen Fu
AU - Chen, Yu Wen
AU - Lu, Hsueh Yu
N1 - Funding Information:
Our research team collected the data for this study during pumping tests executed by the Central Geological Survey (CGS) of Taiwan. We are encouraged to release the raw data under an agreement with CGS of Taiwan. The inverted data can be acquired freely. For more information simply contact Dr. Chang, Ping-Yu via email ([email protected]). This study was funded by the Central Geological Survey, MOEA, R.O.C. We are grateful for the help from the pumping-test engineers at the Taiwan Sugar Company.
PY - 2016
Y1 - 2016
N2 - We conducted a time-lapse monitoring study during a well-pumping test at the Pengtsuo site in Pingtung, Taiwan. Water-level gauges were installed in four wells (P1, W1, O1, and O2) at the Pengtsuo site with different screen depths for the observation. We designed the pumping test to be executed in three phases: The background, the stepwise-pumping, and the continuous-pumping phases. The survey line crossed the four wells so that a comparison would be possible between the resistivity measurements and the water-level records. The resistivity differences relative to the pre-pumping background show that electrical resistivity imaging (ERI) can resolve changes due to dewatering from pumping activity. The time-lapse resistivity images reveal that the maximum resistivity increase took place at the locations in the vadose zone instead of at the groundwater surface. The variation in the resistivity differences in the vadose zone correlated to the change in groundwater level in the stepwise phase. On the other hand, the resistivity-difference change was not fully consistent with the groundwater-level change in the continuous-pumping phase. We attribute the abnormal ERI signals to the dynamic non-equilibrium of the water movement in the vadose zone. The findings suggest that pumping designs can affect the changing resistivity differences and water-content distribution patterns. We show the potential of the ER method to reveal both the water flow and water-content changes in the vadose zone with different transient boundary conditions.
AB - We conducted a time-lapse monitoring study during a well-pumping test at the Pengtsuo site in Pingtung, Taiwan. Water-level gauges were installed in four wells (P1, W1, O1, and O2) at the Pengtsuo site with different screen depths for the observation. We designed the pumping test to be executed in three phases: The background, the stepwise-pumping, and the continuous-pumping phases. The survey line crossed the four wells so that a comparison would be possible between the resistivity measurements and the water-level records. The resistivity differences relative to the pre-pumping background show that electrical resistivity imaging (ERI) can resolve changes due to dewatering from pumping activity. The time-lapse resistivity images reveal that the maximum resistivity increase took place at the locations in the vadose zone instead of at the groundwater surface. The variation in the resistivity differences in the vadose zone correlated to the change in groundwater level in the stepwise phase. On the other hand, the resistivity-difference change was not fully consistent with the groundwater-level change in the continuous-pumping phase. We attribute the abnormal ERI signals to the dynamic non-equilibrium of the water movement in the vadose zone. The findings suggest that pumping designs can affect the changing resistivity differences and water-content distribution patterns. We show the potential of the ER method to reveal both the water flow and water-content changes in the vadose zone with different transient boundary conditions.
KW - Dynamic non-equilibrium effect
KW - Time-lapse resistivity
KW - Transient boundary condtion
UR - http://www.scopus.com/inward/record.url?scp=84963968524&partnerID=8YFLogxK
U2 - 10.3319/TAO.2015.08.20.01(T)
DO - 10.3319/TAO.2015.08.20.01(T)
M3 - 期刊論文
AN - SCOPUS:84963968524
SN - 1017-0839
VL - 27
SP - 59
EP - 71
JO - Terrestrial, Atmospheric and Oceanic Sciences
JF - Terrestrial, Atmospheric and Oceanic Sciences
IS - 1
ER -