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Faulting and groundwater in a desert environment: constraining hydrogeology using time-domain electromagnetic data

Near Surface Geophysics

By:
, ,
DOI: 10.3997/1873-0604.2013043

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Abstract

Within the south-western Mojave Desert, the Joshua Basin Water District is considering applying imported water into infiltration ponds in the Joshua Tree groundwater sub-basin in an attempt to artificially recharge the underlying aquifer. Scarce subsurface hydrogeological data are available near the proposed recharge site; therefore, time-domain electromagnetic (TDEM) data were collected and analysed to characterize the subsurface. TDEM soundings were acquired to estimate the depth to water on either side of the Pinto Mountain Fault, a major east-west trending strike-slip fault that transects the proposed recharge site. While TDEM is a standard technique for groundwater investigations, special care must be taken when acquiring and interpreting TDEM data in a twodimensional (2D) faulted environment. A subset of the TDEM data consistent with a layered-earth interpretation was identified through a combination of three-dimensional (3D) forward modelling and diffusion time-distance estimates. Inverse modelling indicates an offset in water table elevation of nearly 40 m across the fault. These findings imply that the fault acts as a low-permeability barrier to groundwater flow in the vicinity of the proposed recharge site. Existing production wells on the south side of the fault, together with a thick unsaturated zone and permeable near-surface deposits, suggest the southern half of the study area is suitable for artificial recharge. These results illustrate the effectiveness of targeted TDEM in support of hydrological studies in a heavily faulted desert environment where data are scarce and the cost of obtaining these data by conventional drilling techniques is prohibitive.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Faulting and groundwater in a desert environment: constraining hydrogeology using time-domain electromagnetic data
Series title:
Near Surface Geophysics
DOI:
10.3997/1873-0604.2013043
Volume
11
Issue:
5
Year Published:
2013
Language:
English
Publisher:
European Association of Geoscientists & Engineers
Contributing office(s):
California Water Science Center
Description:
9 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
545
Last page:
555