Validated algorithms for fully coupled 3-D inversion

This report is deliverable D12 of ENIGMA ITN project. "The transport of fluids and their constituents in the subsurface causes a change in the physical properties of the medium. The aim of hydrogeophysical investigations is to study these changes by geophysical surveying techniques in order to infer the groundwater flow and solute transport behavior in the investigated domain, estimate hydraulic, geophysical and other material properties, and predict the system behavior under changing boundary conditions. Hydrogeological data such as hydraulic heads, tracer concentrations, or derived variables such as solutes travel times provide additional information to the geophysical data. While combining data of such disparate nature should theoretically improve the accuracy of the subsurface description, it also adds complexity, introduces additional properties to be considered (which are non-uniform and uncertain by themselves) and can cause inconsistent interpretations. Therefore, the joint analysis of geophysical and hydrogeological data is an active area of research. The aim of this report is to give an overview of existing algorithms to jointly use hydrological and geophysical data in a single problem set.