Physics-guided deep learning model for daily groundwater table maps
estimation using passive surface-wave dispersion
Abstract
Monitoring groundwater tables (GWTs) is challenging due to limited
spatial and temporal observations. This study presents an innovative
approach utilizing supervised deep learning, specifically a Multilayer
Perceptron (MLP), and continuous passive-Multichannel Analysis of
Surface Waves (passive-MASW) for constructing 2D GWT level maps. The
study site, geologically well-constrained, features two 20-meter-deep
piezometers and a permanent 2D geophone array capturing train-induced
surface waves. For each point of the 2D array, dispersion curves (DCs),
displaying Rayleigh-wave phase velocities (V_R) across a frequency
range of 5 to 50 Hz, have been computed each day between December 2022
and September 2023. In the present study, these DCs are resampled in
wavelengths ranging from 4 to 15~m in order to focus the
monitoring on the expected GWT levels (between -1 and -5 m). Nine months
of daily V_R data around one of the two piezometers is used to train
the MLP model. GWT levels are then estimated across the entire geophone
array, generating daily 2D GWT maps. Model’s performance is tested
through cross-validation and comparisons with GWT level data at the
second piezometer. Model’s efficiency is quantified with the
root-mean-square error (RMSE) and the coefficient of determination (R²).
The R² is estimated at 80% for data surrounding the training
piezometer, and at 68% for data surrounding the test piezometer.
Additionally, the RMSE is impressively low at 0.03 m at both
piezometers. Results showcase the effectiveness of DL in estimating GWT
level maps from passive-MASW data, offering a practical and efficient
monitoring solution across broader spatial extents.