TESTING FOURNIER METHOD FOR FINDING WATER-TABLE FROM SELF-POTENTIAL

Fournier's approximate method for relating self-potential anomalies to water-table elevation is satisfactory for five of the six sites where it has been tested in New Hampshire. At these sites water-table elevations were determined independently from observation of surface-water bodies and by seismic refraction at the times of the self-potential surveys. At three sites on drumlins formed of glacial till, the apparent coupling coefficients range from 0.95 to 4 mV/m whereas two surveys on sand and gravel deltas yield apparent coupling coefficients of - 16 and - 17 mV/m. At a third delta the apparent coupling coefficient suggests that the water table is in an underlying till rather than in the deltaic deposits. Modeling of self-potential anomalies using Fournier's method may permit isolation of anomalies caused by sources other than ground-water flow as well as location of significant geological inhomogeneities. Because of nonuniqueness it is not possible to determine water-table elevations from self-potential surveys alone.