Three-Dimensional Steady-State Hydraulic Tomography Analysis With Integration of Cross-Hole Flowmeter Data at a Highly Heterogeneous Site

Hydraulic tomography (HT) has been shown to be a robust approach for the high-resolution characterization of subsurface heterogeneity. However, HT can yield smooth estimates of hydraulic parameters when pumping tests and drawdown measurements are sparse, thus limiting the utility of characterization results in predicting groundwater flow and solute transport. To overcome this issue, this study integrates cross-hole flowmeter measurements with HT analysis of steady-state pumping/injection test data for the three-dimensional (3-D) characterization of hydraulic conductivity (K) at a highly heterogeneous glaciofluvial deposit site, which has not been previously attempted. Geostatistical inverse analyses of cross-hole flowmeter data are conducted to yield preliminary estimates of K distribution, which are then utilized as initial K fields for steady-state HT analysis of head data. Four cases combining three data types (geological information, cross-hole flowmeter measurements, and steady-state head data) for inverse modeling are performed. Model calibration and validation results from all cases are compared qualitatively and quantitatively to evaluate their performances. Results from this study show that (a) geostatistical inverse analysis of cross-hole flowmeter data is capable in revealing vertical distributions of K at well locations and major high/low K zones between wells, (b) cross-hole flowmeter data carry non-redundant information of K heterogeneity compared to geological information and steady-state head data, and (c) integration of flowmeter data improves characterization results in terms of revealing K heterogeneity details and predicting independent hydraulic test data. Therefore, this study demonstrates the usefulness of cross-hole flowmeter data in augmenting HT surveys for improved K characterization in 3-D.