TY - JOUR

T1 - Modeling Diffusivity Tests in Heterogeneous Aquifers

T2 - A Stochastic First-Order Approach

AU - Cheng, Kan Bun

AU - Dagan, Gedeon

AU - Rabinovich, Avinoam

N1 - Publisher Copyright:
© 2020. American Geophysical Union. All Rights Reserved.

PY - 2020/9/1

Y1 - 2020/9/1

N2 - The diffusivity test considered here consists of injecting (or pumping) a volume of water through short segments of a well for a short time and measuring the travel time of the peak of the head signal at different points in the surrounding aquifer volume. The specific storage is assumed to be constant, while the hydraulic conductivity of the heterogeneous aquifer is modeled as a random lognormal field. The axi-symmetric anisotropic structure is characterized by a few parameters (logconductivity mean and variance and horizontal and vertical integral scales). The paper determines the mean and variance of the peak travel time as function of distance from an instantaneous source by solving the flow equation using a first-order approximation in the logconductivity variance. The mean travel time is recast in terms of the equivalent conductivity, which decreases from the harmonic mean near the source to the effective conductivity in uniform flow for a sufficiently large distance. Similarly, the variance drops from its maximum near the source to a small value. Application to field test is discussed and topics of future investigations are suggested.

AB - The diffusivity test considered here consists of injecting (or pumping) a volume of water through short segments of a well for a short time and measuring the travel time of the peak of the head signal at different points in the surrounding aquifer volume. The specific storage is assumed to be constant, while the hydraulic conductivity of the heterogeneous aquifer is modeled as a random lognormal field. The axi-symmetric anisotropic structure is characterized by a few parameters (logconductivity mean and variance and horizontal and vertical integral scales). The paper determines the mean and variance of the peak travel time as function of distance from an instantaneous source by solving the flow equation using a first-order approximation in the logconductivity variance. The mean travel time is recast in terms of the equivalent conductivity, which decreases from the harmonic mean near the source to the effective conductivity in uniform flow for a sufficiently large distance. Similarly, the variance drops from its maximum near the source to a small value. Application to field test is discussed and topics of future investigations are suggested.

KW - Diffusivity test

KW - Equivalent conductivity

KW - Heterogeneous aquifers

KW - Hydraulic tomography

KW - Pumping test

KW - Source flow

UR - http://www.scopus.com/inward/record.url?scp=85092133773&partnerID=8YFLogxK

U2 - 10.1029/2020WR027672

DO - 10.1029/2020WR027672

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AN - SCOPUS:85092133773

VL - 56

JO - Water Resources Research

JF - Water Resources Research

SN - 0043-1397

IS - 9

M1 - e2020WR027672

ER -