A system for continuous resistivity monitoring was installed in Haellby embankment dam in 1996. The results from three years measurements show a seasonal resistivity variation in the dam. This depends on the seepage flow, which influences the resistivity due to the seasonal variation in temperature and concentration of total dissolved solids in the reservoir. However, freezing, soil moisture and electrical disturbances also affect the resistivity data. The seepage flow was evaluated from one-year resistivity data using methods similar to those employed for seepage evaluation from temperature data. Resistivity monitoring is non-destructive apart from the electrode installation and can also provide measurements of time-dependent processes such as internal erosion. The seasonal resistivity variation implies that resistivity measurement at a single time in a dam must be interpreted carefully as the result is incomplete without the time variation. The SP data recorded at Haellby using stainless steel electrodes show a stable character with seasonal variation. The results may to some extent indicate zones of increased leakage. However, the initial electrode tests at Saedva indicate that strong polarisation effects may be associated with the stainless steel electrodes, so the results should be interpreted with caution Overall results and experience do not yet allow an installation of an automatic monitoring and evaluation system. However, both monitoring and evaluation methods can be improved and such a system seems to be possible to achieve in the future. The method may then be an alternative for seepage monitoring in existing dams, without seepage monitoring systems, or where conventional seepage monitoring is complicated.
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