Frequency dependent hydraulic properties estimated from oscillatory pumping tests in an unconfined aquifer

The emergence of stochastic subsurface hydrology stemmed from the realization that the random spatial variability of aquifer properties has a profound impact on solute transport. The last four decades witnessed a tremendous expansion of the discipline, many fundamental processes and principal mechanisms being identified. However, the research findings have not impacted significantly the application in practice, for several reasons which are discussed. The paper discusses the current status of stochastic subsurface hydrology, the relevance of the scientific results for applications and it also provides a perspective to a few possible future directions. In particular, we discuss how the transfer of knowledge can be facilitated by identifying clear goals for characterization and modeling application, relying on recent recent advances in research in these areas.

Section: How Relevant Are the Advances Of The Last 30 Years To Practimentioning

confidence: 99%

Debates—Stochastic subsurface hydrology from theory to practice: The relevance of stochastic subsurface hydrology to practical problems of contaminant transport and remediation. What is characterization and stochastic theory good for?

Fiori

Cvetković

Dagan

et al. 2016

“…Rabinovich et al . [] used harmonic pumping tests to estimate the effective storativity, specific yield, and hydraulic conductivity of the Boise Hydrogeophysical Research Site in USA.…”

Section: Introductionmentioning

confidence: 98%

“…Bakhos et al [2014] presented a least squares based technique to filter the sinusoidal signal associated with harmonic pumping tests and performed the joint inversion of storativity and hydraulic conductivity using HHT. Rabinovich et al [2015] used harmonic pumping tests to estimate the effective storativity, specific yield, and hydraulic conductivity of the Boise Hydrogeophysical Research Site in USA.…”

Section: Introductionmentioning

confidence: 99%

Joint inversion of hydraulic head and self‐potential data associated with harmonic pumping tests

Ahmed

Jardani

Revil

et al. 2016

Harmonic pumping tests consist in stimulating an aquifer by the means of hydraulic stimulations at some discrete frequencies. The inverse problem consisting in retrieving the hydraulic properties is inherently ill posed and is usually underdetermined when considering the number of well head data available in field conditions. To better constrain this inverse problem, we add self‐potential data recorded at the ground surface to the head data. The self‐potential method is a passive geophysical method. Its signals are generated by the groundwater flow through an electrokinetic coupling. We showed using a 3‐D saturated unconfined synthetic aquifer that the self‐potential method significantly improves the results of the harmonic hydraulic tomography. The hydroelectric forward problem is obtained by solving first the Richards equation, describing the groundwater flow, and then using the result in an electrical Poisson equation describing the self‐potential problem. The joint inversion problem is solved using a reduction model based on the principal component geostatistical approach. In this method, the large prior covariance matrix is truncated and replaced by its low‐rank approximation, allowing thus for notable computational time and storage savings. Three test cases are studied, to assess the validity of our approach. In the first test, we show that when the number of harmonic stimulations is low, combining the harmonic hydraulic and self‐potential data does not improve the inversion results. In the second test where enough harmonic stimulations are performed, a significant improvement of the hydraulic parameters is observed. In the last synthetic test, we show that the electrical conductivity field required to invert the self‐potential data can be determined with enough accuracy using an electrical resistivity tomography survey using the same electrodes configuration as used for the self‐potential investigation.

“…This can be attained by making use of a system (or battery) of pumping wells (Environmental Protection Agency, ; Kitanidis & McCarty, ; Luo et al, ; Suthersan et al, ). Unsteady flow field, produced by oscillatory pumping wells, has been proposed in hydraulic tomography for inferring the aquifer properties (e.g., Cardiff & Barrash, ; Cardiff et al, ; Dagan & Rabinovich, ; Johnson et al, ; Kuo, ; Rabinovich et al, ; Renner & Messar, ). To the best of our knowledge, only a limited number of works consider the impact of transient flow fluctuations on transport in spatially heterogeneous aquifers (e.g., Chang et al, ; Cirpka & Attinger, ; Dentz & Carrera, ; Libera et al, ; Neupauer et al, ).…”

Section: Introductionmentioning

confidence: 99%

Improving the Efficiency of 3‐D Hydrogeological Mixers: Dilution Enhancement Via Coupled Engineering‐Induced Transient Flows and Spatial Heterogeneity

Dato

Barros

Fiori

et al. 2018

Natural attenuation and in situ oxidation are commonly considered as low‐cost alternatives to ex situ remediation. The efficiency of such remediation techniques is hindered by difficulties in obtaining good dilution and mixing of the contaminant, in particular if the plume deformation is physically constrained by an array of wells, which serves as a containment system. In that case, dilution may be enhanced by inducing an engineered sequence of injections and extractions from such pumping system, which also works as a hydraulic barrier. This way, the aquifer acts as a natural mixer, in a manner similar to the industrialized engineered mixers. Improving the efficiency of hydrogeological mixers is a challenging task, owing to the need to use a 3‐D setup while relieving the computational burden. Analytical solutions, though approximated, are a suitable and efficient tool to seek the optimum solution among all possible flow configurations. Here we develop a novel physically based model to demonstrate how the combined spatiotemporal fluctuations of the water fluxes control solute trajectories and residence time distributions and therefore, the effectiveness of contaminant plume dilution and mixing. Our results show how external forcing configurations are capable of inducing distinct time‐varying groundwater flow patterns which will yield different solute dilution rates.