Mapping soil salinity and a fresh-water intrusion in three-dimensions using a quasi-3d joint-inversion of DUALEM-421S and EM34 data.
In order to understand the drivers of topsoil salinization, the distribution and movement of salt in accordance with groundwater need mapping. In this study, we described a method to map the distribution of soil salinity, as measured by the electrical conductivity of a saturated soil-paste extract (ECe), and in 3-dimensions around a water storage reservoir in an irrigated field near Bourke, New South Wales, Australia. A quasi-3d electromagnetic conductivity image (EMCI) or model of the true electrical conductivity (σ) was developed using 133 apparent electrical conductivity (ECa) measurements collected on a 50m grid and using various coil arrays of DUALEM-421S and EM34 instruments. For the DUALEM-421S we considered ECain horizontal coplanar (i.e., 1mPcon, 2mPcon and 4mPcon) and vertical coplanar (i.e., 1mHcon, 2mHcon and 4mHcon) arrays. For the EM34, three measurements in the horizontal mode (i.e., EM34-10H, EM34-20H and EM34-40H) were considered. We estimated σ using a quasi-3d joint-inversion algorithm (EM4Soil). The best correlation (R2=0.92) between σ and measured soil ECewas identified when a forward modelling (FS), inversion algorithm (S2) and damping factor (λ=0.2) were used and using both DUALEM-421 and EM34 data; but not including the 4m coil arrays of the DUALEM-421S. A linear regression calibration model was used to predict ECein 3-dimensions beneath the study field. The predicted ECewas consistent with previous studies and revealed the distribution of ECeand helped to infer a freshwater intrusion from a water storage reservoir at depth and as a function of its proximity to near-surface prior stream channels and buried paleochannels. It was concluded that this method can be applied elsewhere to map the soil salinity and water movement and provide guidance for improved land management.
School of Biological, Earth and Environmental Sciences, UNSW Australia, Kensington, NSW 2052, Australia.
J
J
Huang
School of Biological, Earth and Environmental Sciences, UNSW Australia, Kensington, NSW 2052, Australia.
T
T
Koganti
Faculty of Sciences, University of Lisbon, DEGGE Campo Crande Ed C8, Lisbon 1749-016, Portugal.
F A Monteiro
FA
Santos
School of Biological, Earth and Environmental Sciences, UNSW Australia, Kensington, NSW 2052, Australia. Electronic address: j.triantafilis@unsw.edu.au.
J
J
Triantafilis
Discharge; EM4Soil; Recharge; Salinity management; Secondary salinisation