Prediction of solute transport in a heterogeneous aquifer utilizing hydraulic conductivity and specific storage tomograms

Abstract

A sequential procedure of hydraulic tomographical inversion is applied to characterize at high resolution the spatial heterogeneity of hydraulic conductivity and specific storage at the field test site Stegem€ uhle, Germany. The shallow aquifer at this site is examined by five short-term multilevel pumping tests with 30 pumping-observation pairs between two wells. Utilizing travel time diagnostics of the recorded pressure response curves, fast eikonal-based inversion is shown to deliver insight into the sedimentary structures. Thus, the structural information from the generated travel time tomogram is exploited to constrain full calibration of the pressure response curves. Based on lateral extrapolation from the measured inter-well profile, a three-dimensional reconstruction of the aquifer is obtained. It is demonstrated that calibration of spatially variable specific storage in addition to hydraulic conductivity can improve the fitting of the model while the structural features are only slightly changed. At the field site, two tracer tests with uranine and sodium-naphthionate were also performed and their concentrations were monitored for 2 months. The measured tracer breakthrough curves are employed for independent validation of the hydraulic tomographical reconstruction. It is demonstrated that major features of the observed solute transport can be reproduced, and structures relevant for macrodispersive tracer spreading could be resolved. However, for the mildly heterogeneous aquifer, the tracer breakthrough curves can also be approximated by a simplified homogeneous model with higher dispersivity. Therefore, improved validation results that capture specific characteristics of the breakthrough curves would require additional hydraulic measurements.

Field validation of thermal tracer tomography for reconstruction of aquifer heterogeneity

“…This lack of field tests may be due to the demanding experimental design and instrumentation, the need for in situ tracer monitoring or repeated multilevel sampling, and the time and cost for carrying out a full experiment. Therefore, tracers are more commonly applied to validate or complement other hydrogeological or hydrogeophysical field tests [Sharmeen et al, 2012;Dorn et al, 2013;Jim enez et al, 2015;Sanchez-Le on et al, 2016].…”

Smart pilot points using reversible‐jump Markov‐chain Monte Carlo

“…Due to the relatively demanding field implementation and the challenge of combined tracer data inversion, only a few studies on tracer tomography have been presented so far [ Brauchler et al ., ; Illman et al ., ]. Variants include applications with solute tracers [ Vasco and Datta‐Gupta , ; Jiménez et al ., ], thermal tracer tomography [ Klepikova et al ., ], and combinations with geophysical methods such as electrical resistivity tomography (ERT) [ Singha and Gorelick , ] and ground penetrating radar (GPR) [ Dorn et al ., ].…”

Bayesian Monitoring Design for Streambed Heat Tracing: Numerical Simulation and Sandbox Experiments

“…It is well recognized that the heterogeneity of hydraulic conductivities significantly impacts flow and transport processes in shallow streambeds Liu and Chui 2017). Thus, for better management, conservation and restoration of riverine ecosystems, it is essential to accurately characterize the heterogeneous streambed (Cardenas 2015;Jiménez et al 2015). Due to difficulties in measuring the hydraulic conductivity directly, there are increasing interests in applying inverse modeling methods to estimate it from indirect measurements of state variables in groundwater hydrology (Zhu et al 2017;Lan et al 2018;Liao et al 2018;Zha et al 2018).…”