Abstract: Subsurface monitoring can include obtaining a first set of subsurface resistivity measurements at a first time using a subsurface monitoring apparatus and obtaining a second set of subsurface resistivity measurements at a second different time using the subsurface monitoring apparatus. The second set of subsurface resistivity measurements can be compared to the first set of subsurface resistivity measurements, for instance at the subsurface monitoring apparatus or another component in a system. A notification can be generated when the second set of subsurface resistivity measurements differs from the first set of subsurface resistivity measurements by a first predetermined threshold. The subsurface monitoring apparatus can include a main controller and a plurality of electrode probes that extend a distance into a ground surface. A remote server can be in communication with the subsurface monitoring apparatus over a network.