Twenty-three resistivity pseudosections and electromagnetic lines were conducted about twelve crystalline rock water wells located in San Diego County, California. The electromagnetic survey data was used in the interpretation of the pseudosections. The interpreted resistivity sections were compared with the hydraulic conductivities calculated from pump tests, with mapped lineaments, and with well logs. The dipole-dipole method appears capable of detecting lineaments and the general rock weathering condition. The ground water table appears to be detectable only in relatively unweathered rocks. Well site hydraulic conductivity can be significantly improved by locating the well off interpreted conductive anomalies. These anomalies are likely due to clay zones of low permeability.
