Use of Time-lapse Mise-á-la-Masse Measurements to Monitor a Saline Tracer Test: Advantages and Limitations.

Abstract:

This work presents the results of a saline tracer test conducted on an alluvial aquifer placed in the Alento River Valley (Campania region, Southern Italy) and monitored by time-lapse Mise-á-la-Masse measurements. The principal aim of this study is the characterization of the groundwater flow field, both in velocity and direction. The results of the geophysical survey are described and compared to several simulated datasets conducted on a 3D model simulating flow, transport and electrical current. In this manner it is possible to assess the information content of the Mise-á-la-Masse dataset with respect to the groundwater field characteristics. The study shows how a combination of three-dimensional time-lapse modelling of flow, tracer transport and electrical current can substantially contribute towards a quantitative interpretation of Mise-á-la-Masse measurements during saline tracer tests. This approach can thus revive the use of Mise-á-la-Masse as a practical, low cost field technique for tracer test monitoring, particularly for shallow aquifers, providing critical information concerning the natural groundwater flow direction and velocity.