Identification of reability limits in the transfer function approach for the solution of inverse problems in groundwater transport. Abstract H14C-03

In recent time a great attention is devoted to the solution of inverse problems in groundwater and, more specifically, in pollution transport. One of the main problems occurring in literature is the identification of the location of the pollutant source of the release history of the pollutant injection. Such information is deduced by the analysis of the pollutant concentration measured in monitoring points located in the aquifer. The reliability of the results of the different numerical procedures depends on several factors linked up with the presence of errors in the main data as important measurement errors, uncertainty in the knowledge of the aquifer parameters, etc. Nevertheless, the transport process itself, because of the effect of the dispersion, can be the reason for unreliable results of such procedures: in fact the role of the dispersion can hide the original characteristics of the release history smoothing peak values and broadening the duration of impulsive release. Moreover, the identification of the source can lead to a low confidence location since a too-wide area can be suspected to contain the font of pollution. As an example if the monitoring point is too far from the source or a long time is elapsed from the release the detected concentrations can be useless for the inversion procedure. In this work we identify threshold criteria that can, a priori, define if the inversion procedure can lead to reliable or unreliable results in order to distinguish the uncertainty due to the dispersion process itself from the measurement and hydraulic parameter errors. We have experience in the geostatistic approach for the restoring of the release history that is based on the use of the transfer function: starting from the analysis of the transfer function in a monitoring point we define the criteria which allow the forecast of unreliable solution of the inverse proble