Application of electrical sounding to determine the spatial distribution of groundwater quality in the coastal area of Jiangsu Province, China

Abstract

In most coastal alluvial plains, the groundwater area of the aquifer is a rich environment that has experienced an extended period of marine deposition and is highly vulnerable to increasing urbanization. Excessive exploitation of groundwater has resulted in recent seawater intrusion and connate water leakage, leading to freshwater salinization. In this study, a novel workflow is designed for groundwater appraisal. First, revised one-dimensional direct transformation schemes were developed and applied to extensive vertical electrical sounding (VES) points sampled by a Schlumberger array to obtain the VES-based calibrated transformed resistivity (V-CTR), as calibrated by the modified reflection coefficient and novel depth correction factor. Next, the interfaces of all leaky confined aquifers (LCAs) and the saline water zone were quantitatively determined via hybrid interpretation methods. Finally, to better understand the salt level (i.e., fresh, brackish, or saline) and perform assessments of the groundwater quality, total dissolved solids (TDS) planar distributions were interpolated using two different power functions linking the V-CTR and measured TDS from the sampled boreholes for the corresponding aquifer unit. The workflow was examined based on hydrological and geophysical data acquired at the Yangtze River Delta (Nantong Region, Jiangsu Province, China). The interpreted results are of great significance for understanding the groundwater distribution associated with the Quaternary geology and hydrogeology and can be potentially used to analyze and guide the development and utilization of water resources in the study area.