Abstract: A combined high resolution short offset transient electromagnetic (SHOTEM) and deep sounding, long offset (LOTEM) survey has been carried out along two traverses between the Mediterranean Sea and the Jordan-Dead Sea Rift (DSR). The DSR is located in the study area some 200–250m below sea level. The measurements detected a deep conductor, the top of which exhibited a regular behavior along the both traverses, declining from the Mediterranean to the DSR base level. The geometry of this geoelectric boundary coincides fairly well with the configuration of a supposed fresh/saline groundwater interface as also obtained by both numerical and physical modeling for the known hydrogeological conditions in the study area. Therefore the detected geoelectric boundary is identified with the interface, supporting the hypothesis of current seawater intrusion into the deep regional aquifers between the Mediterranean and the DSR base levels. The intrusion causes the salination of fresh groundwater within the aquifers as well as the salination of the Sea of Galilee.

Abstract: Groundwater is an important water resource for agricultural irrigation and urban and industrial utilization in the coastal regions of northern China. In the past 5 decades, coastal groundwater salinization in the Yang–Dai river plain has become increasingly serious under the influence of anthropogenic activities and climatic change. It is pivotal for the scientific management of coastal water resources to accurately understand groundwater salinization processes and their causative factors. Hydrochemical (major ion and trace element) and stable isotopic (δ18O and δ2H) analysis of different water bodies (surface water, groundwater, geothermal water and seawater) were conducted to improve understanding of groundwater salinization processes in the plain's Quaternary aquifer. Saltwater intrusion due to intensive groundwater pumping is a major process, either by vertical infiltration along riverbeds which convey saline surface water inland, and/or direct subsurface lateral inflow. Trends in salinity with depth indicate that the former may be more important than previously assumed. The proportion of seawater in groundwater is estimated to have reached up to 13 % in shallow groundwater of a local well field. End-member mixing calculations also indicate that the geothermal water with high total dissolved solids (up to 10.6 g L−1) with depleted stable isotope compositions and elevated strontium concentrations (> 10 mg L−1) also mixes locally with water in the overlying Quaternary aquifers. This is particularly evident in samples with elevated Sr ∕ Cl ratios (> 0.005 mass ratio). Deterioration of groundwater quality by salinization is also clearly exacerbated by anthropogenic pollution. Nitrate contamination via intrusion of heavily polluted marine water is evident locally (e.g., in the Zaoyuan well field); however, more widespread nitrate contamination due to other local sources such as fertilizers and/or domestic wastewater is evident on the basis of NO3 ∕ Cl ratios. This study provides an example of how multiple geochemical indicators can delineate different salinization processes and guide future water management practices in a densely populated water-stressed coastal region.