The capability of a new geo-electrical monitoring system to be used for permanent monitoring of tailings dams is presented. G.RE.T.A. (Geo REsistivimeter for Time-lapse Analysis), is an autonomous programmable system including a remotely controlled low-power resistivity meter with two cables that can be permanently buried in shallow trenches. Time-lapse data analysis algorithms to visualize resistivity differences for any desired measurements are available on a cloud to monitor the subsoil in real-time. An automatic control algorithm can detect whether changes have approached predefined thresholds to send alarms about anomalous changes to the customer. The efficiency of the system has been demonstrated in pilot sites for monitoring the internal conditions of river levees and through laboratory tests for shallow landslides. The system is being used in several projects regarding tailings dams monitoring.