Detecting saline water plume in a heterogeneous synthetic aquifer through a combination of POD and geoelectrical surveys

In recent decades, geoelectrical surveys have been progressively used to capture the geometry and evolution of contaminant plumes in groundwater systems. In this study, we examine a procedure of a combination of proper orthogonal decomposition (POD) and geoelectrical forward and inversion models to map the salinity plume inside a heterogeneous synthetic aquifer through the surface resistivity data. Here, we improve the framework presented by Oware et al. (2013) in which they used POD as part of the geoelectric inversion stage needing a higher memory and time to run as well as using a finite difference approach. More importantly, the center of mass of the final modeled plume obtained from their methodology required to be shifted to the mass center of the original plume, resulting in the inapplicability of the method for the real cases in which the mass center of the plume is still unknown before modeling. Since the POD method is separately performed prior to the geoelectrical models and also solved through the finite-element rather than the finite-difference approach, the presented procedure, in addition to decrease the required RAM capacity, can correctly capture the spatial distribution and geometry of the salinity plume without the need for shifting the mass center of the modeled plume, so that, it can be reasonably used for real cases. Moreover, the findings from the three different scenarios of salinity injection (single injection point on the border, single injection point somewhere inside the aquifer, and two injection points somewhere inside the aquifer) show that the border effect may cause a horizontal shift in the modeled plume compared to the reference case. Additionally, the results indicate that the strength of the method for detecting the geometry of the plume decreases with depth.