Combining 3D Hydraulic Tomography with Tracer Tests for Improved Transport Characterization

Area of Science:

• Hydrogeology
• Geophysics
• Environmental Science

Background:

• Hydraulic tomography (HT) offers partial resolution of aquifer hydraulic parameters, but often misses details crucial for accurate solute transport modeling.
• Unresolved aquifer heterogeneity significantly challenges the prediction of contaminant or solute movement.

Purpose of the Study:

• To develop and validate a methodology for enhancing solute transport predictions by integrating hydraulic tomography data with single forced-gradient tracer test breakthrough curves (BTCs).
• To improve the characterization of three-dimensional (3D) hydraulic conductivity fields and transport parameters in alluvial aquifers.

Main Methods:

• Estimated the 3D hydraulic conductivity field using pilot-point inversion of tomographic pumping tests.
• Validated the conductivity field with independent hydraulic head measurements and direct-push injection logging (DPIL) data.
• Estimated dual-domain transport parameters by fitting breakthrough curve data from a forced-gradient tracer test.

Main Results:

• Successfully estimated a 3D hydraulic conductivity field and validated it against independent measurements.
• Utilized dual-domain transport modeling to account for unresolved aquifer heterogeneity and accurately fit tracer breakthrough curve data.
• Demonstrated the predictive capability of the integrated approach by accurately forecasting a second, independent tracer test.

Conclusions:

• The proposed methodology provides an efficient and practical approach for predicting solute transport in complex, heterogeneous aquifers.
• Combining hydraulic tomography with tracer test data significantly improves solute transport predictions compared to using HT alone.
• This approach reduces the need for extensive and complex field tracer studies for reliable transport modeling.