Three-dimensional imaging of aquifer and aquitard heterogeneity via transient hydraulic tomography at a highly heterogeneous field site

•Long-term drawdowns are used for transient hydraulic tomography (THT) analyses.•Geostatistical approach (GA) yields the best calibration and validation performances.•Drawdowns from aquitards improve hydraulic conductivity estimates for the GA.•Reliable geological data are useful for THT analyses at...

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Bibliographic Details
Published in:Journal of hydrology (Amsterdam) Vol. 559; no. C; pp. 392 - 410
Main Authors: Zhao, Zhanfeng, Illman, Walter A.
Format: Journal Article
Language:English
Published: Netherlands Elsevier B.V 01.04.2018
Elsevier
Subjects:
aquifers
Aquitard characterization
digital images
drawdown
geostatistics
hydraulic conductivity
Hydraulic tomography
image analysis
Inverse modeling
Model calibration and validation
Model comparison
prediction
spatial distribution
Subsurface heterogeneity
tomography
Subsurface heterogeneity
Aquitard characterization
Model comparison
Hydraulic tomography
Model calibration and validation
Inverse modeling
ISSN:0022-1694, 1879-2707
Online Access:Get full text
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Summary:•Long-term drawdowns are used for transient hydraulic tomography (THT) analyses.•Geostatistical approach (GA) yields the best calibration and validation performances.•Drawdowns from aquitards improve hydraulic conductivity estimates for the GA.•Reliable geological data are useful for THT analyses at highly heterogeneous sites. Previous studies have shown that geostatistics-based transient hydraulic tomography (THT) is robust for subsurface heterogeneity characterization through the joint inverse modeling of multiple pumping tests. However, the hydraulic conductivity (K) and specific storage (Ss) estimates can be smooth or even erroneous for areas where pumping/observation densities are low. This renders the imaging of interlayer and intralayer heterogeneity of highly contrasting materials including their unit boundaries difficult. In this study, we further test the performance of THT by utilizing existing and newly collected pumping test data of longer durations that showed drawdown responses in both aquifer and aquitard units at a field site underlain by a highly heterogeneous glaciofluvial deposit. The robust performance of the THT is highlighted through the comparison of different degrees of model parameterization including: (1) the effective parameter approach; (2) the geological zonation approach relying on borehole logs; and (3) the geostatistical inversion approach considering different prior information (with/without geological data). Results reveal that the simultaneous analysis of eight pumping tests with the geostatistical inverse model yields the best results in terms of model calibration and validation. We also find that the joint interpretation of long-term drawdown data from aquifer and aquitard units is necessary in mapping their full heterogeneous patterns including intralayer variabilities. Moreover, as geological data are included as prior information in the geostatistics-based THT analysis, the estimated K values increasingly reflect the vertical distribution patterns of permeameter-estimated K in both aquifer and aquitard units. Finally, the comparison of various THT approaches reveals that differences in the estimated K and Ss tomograms result in significantly different transient drawdown predictions at observation ports.
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USDOE Office of Electricity (OE), Advanced Grid Research & Development. Power Systems Engineering Research
ISSN:0022-1694
1879-2707
DOI:10.1016/j.jhydrol.2018.02.024