Towed geo-electrode arrays for analysis of surface water groundwater interaction

Abstract

High productivity analysis of surface water groundwater interaction is possible using GPS positioned vertical electrical conductivity imaging along with depth recording. Short submerged geoelectric arrays provide a great deal of detail right at the base of surface water bodies: however they cannot be used in treacherous waterways with debris scattered through them. Long floating arrays can be towed through such waterways and have the additional benefit of greater depth of exploration. Floating arrays also can have reasonable resolution at the base of surface water bodies provided that they are designed optimally and that data from them is inverted effectively. Array design must optimize a balance of signal strength maximization, exploration depth resolution weight and drag minimization crosstalk and current leakage minimization and simple minimal response to three dimensional heterogeneity. Pragmatic interpretation of the huge volumes of data that are typically acquired is best achieved using three dimensional "ribbon' images. Prominent features of interest are in most cases related to groundwater salinity. Low conductivity anomalies often indicate fresh surface water seepage into more saline groundwater. High conductivity anomalies that intersect the bases of surface water bodies usually indicate saline inflow to the surface water bodies.