Theory of transient streaming potentials in coupled unconfined aquifer‐unsaturated zone flow to a well

Malama, Bwalya

doi:10.1002/2013wr014909

Cited by 20 publications

(21 citation statements)

References 60 publications

(143 reference statements)

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“…Their semianalytical solutions can be very useful in benchmarking numerical codes but they do not account for the heterogeneous character of aquifers. This approach has been extended recently by Malama [] to account for the flow in the vadose zone during pumping tests in an unconfined aquifer.…”

Section: Introductionmentioning

confidence: 99%

Hydraulic conductivity field characterization from the joint inversion of hydraulic heads and self‐potential data

Ahmed

Jardani

Revil

et al. 2014

Water Resources Research

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Pumping tests can be used to estimate the hydraulic conductivity field from the inversion of hydraulic head data taken intrusively in a set of piezometers. Nevertheless, the inverse problem is strongly underdetermined. We propose to add more information by adding self-potential data taken at the ground surface during pumping tests. These self-potential data correspond to perturbations of the electrical field caused directly by the flow of the groundwater. The coupling is electrokinetic in nature that is due to the drag of the excess of electrical charges existing in the pore water. These self-potential signals can be easily measured in field conditions with a set of the nonpolarizing electrodes installed at the ground surface. We used the adjoint-state method for the estimation of the hydraulic conductivity field from measurements of both hydraulic heads and self potential during pumping tests. In addition, we use a recently developed petrophysical formulation of the streaming potential problem using an effective charge density of the pore water derived directly from the hydraulic conductivity. The geostatistical inverse framework is applied to five synthetic case studies with different number of wells and electrodes and thickness of the confining unit. To evaluate the benefits of incorporating the self-potential data in the inverse problem, we compare the cases in which the data are combined or not. Incorporating the self-potential information improves the estimate of hydraulic conductivity field in the case where the number of piezometers is limited. However, the uncertainty of the characterization of the hydraulic conductivity from the inversion of the self-potential data is dependent on the quality of the distribution of the electrical conductivity used to solve the Poisson equation. Consequently, the approach discussed in this paper requires a precise estimate of the electrical conductivity distribution of the subsurface and requires therefore new strategies to be developed for the joint inversion of the hydraulic and electrical conductivity distributions.

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Section: Introductionmentioning

confidence: 99%

Hydraulic conductivity field characterization from the joint inversion of hydraulic heads and self‐potential data

Ahmed

Jardani

Revil

et al. 2014

Water Resources Research

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“…July, after additional precipitation occurs on 10 July. Polarity changes in SP data have been observed in association with the onset of head changes from pumping tests (Malama, 2014 Figure 4e).…”

Section: Sp Response To Precipitationmentioning

confidence: 83%

Transpiration‐ and precipitation‐induced subsurface water flow observed using the self‐potential method

Voytek

Barnard

Jougnot

et al. 2019

Hydrological Processes

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Movement of soil moisture associated with tree root‐water uptake is ecologically important but technically challenging to measure. Here, the self‐potential (SP) method, a passive electrical geophysical method, is used to characterize water flow in situ. Unlike tensiometers, which use a measurement of state (i.e., matric pressure) at two locations to infer fluid flow, the SP method directly measures signals generated by water movement. We collected SP measurements in a two‐dimensional array at the base of a Douglas‐fir tree (Pseudotsuga menziesii) in the H.J. Andrews Experimental Forest in western Oregon over 5 months to provide insight on the propagation of transpiration signals into the subsurface under variable soil moisture. During dry conditions, SP data appear to show downward unsaturated flow, whereas nearby tensiometer data appear to suggest upward flow during this period. After the trees enter dormancy in the fall, precipitation‐induced vertical flow dominates in the SP and tensiometer data. Diel variations in SP data correspond to periods of tree transpiration. Changes in volumetric water content occurring from soil moisture movement during transpiration are not large enough to appear in volumetric water content data. Fluid flow and electrokinetic coupling (i.e., electrical potential distribution) were simulated using COMSOL Multiphysics to explore the system controls on field data. The coupled model, which included a root‐water uptake term, reproduced components of both the long‐term and diel variations in SP measurements, thus indicating that SP has potential to provide spatially and temporally dense measurements of transpiration‐induced changes in water flow. This manuscript presents the first SP measurements focusing on the movement of soil moisture in response to tree transpiration.

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“…This model is chosen based on two considerations. First, it has been commonly employed in previous related investigations [ Liang et al ., ; Malama , ; Mathias and Butler , ; Mishra and Neuman , ; Tartakovsky and Neuman , ]. Second, it has been proven in multiple previous studies that this model is physically sound and is amendable to analytical treatment.…”

Section: Mathematical Modelmentioning

confidence: 94%

Base flow recession from unsaturated‐saturated porous media considering lateral unsaturated discharge and aquifer compressibility

Liang

Zhang

et al. 2017

Water Resources Research

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Unsaturated flow is an important process in base flow recessions and its effect is rarely investigated. A mathematical model for a coupled unsaturated‐saturated flow in a horizontally unconfined aquifer with time‐dependent infiltrations is presented. The effects of the lateral discharge of the unsaturated zone and aquifer compressibility are specifically taken into consideration. Semianalytical solutions for hydraulic heads and discharges are derived using Laplace transform and Cosine transform. The solutions are compared with solutions of the linearized Boussinesq equation (LB solution) and the linearized Laplace equation (LL solution), respectively. A larger dimensionless constitutive exponent κD (a smaller retention capacity) of the unsaturated zone leads to a smaller discharge during the infiltration period and a larger discharge after the infiltration. The lateral discharge of the unsaturated zone is significant when κD≤1, and becomes negligible when κD≥100. The compressibility of the aquifer has a nonnegligible impact on the discharge at early times. For late times, the power index b of the recession curve −dQ/dt∼ aQb, is 1 and independent of κD, where Q is the base flow and a is a constant lumped aquifer parameter. For early times, b is approximately equal to 3 but it approaches infinity when t→0. The present solution is applied to synthetic and field cases. The present solution matched the synthetic data better than both the LL and LB solutions, with a minimum relative error of 16% for estimate of hydraulic conductivity. The present solution was applied to the observed streamflow discharge in Iowa, and the estimated values of the aquifer parameters were reasonable.

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Theory of transient streaming potentials in coupled unconfined aquifer‐unsaturated zone flow to a well

Cited by 20 publications

References 60 publications

Hydraulic conductivity field characterization from the joint inversion of hydraulic heads and self‐potential data

Hydraulic conductivity field characterization from the joint inversion of hydraulic heads and self‐potential data

Transpiration‐ and precipitation‐induced subsurface water flow observed using the self‐potential method

Base flow recession from unsaturated‐saturated porous media considering lateral unsaturated discharge and aquifer compressibility

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