Electromagnetic and Self-potential Investigation to Detect Seepage of Irrigation Canals

We adopted electromagnetic induction (EMI) and self-potential measurements along irrigation canal bank in order to detect groundwater seepage. The EMI methods is sensitive to the electrical conductivity of the subsoil, that is affected by the salt and clay content and water content. The depth of investigation depends on the soil electrical conductivity, the geometry of the instrument and the frequency of the electromagnetic field. The experimental data refers to anintegrated survey along a transect on an irrigation canals (400 m). We acquired broadband electromagnetic data using a Profiler EMP400 (GSSI), with coil separation of 1.22 m and a bandwidth ranging from 1 to 15 kHz. The self-potential measurements were performed with a fixed electrode and a moving electrode along the same transect of EMI measurements. The interval spacing among self-potential measurements was 2 m. Visual inspection of the canal permitted to compare the evidence of seepage losses with the geophysical anomalies. The results of self-potential measurements show peaks of electrical potential at the same position of electrical conductivity anomalies. Integration of the EMI survey and SP measurements is useful to detect seepage losses from canals: a more detailed analysis of self potential anomalies is required to reduce “false” alarms.