Spatial delineation of groundwater salinity using deep TDEM geophysical measurements: a feasibility study
Eldad Levi, Mark Goldman, Avichay Hadad and Haim Gvirtzman

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ABSTRACT

Hydrogeophysics is an evolving research discipline. This feasibility study, as a single step within this evolution, had two objectives: (1) to test the potential application of the improved, deeper-exploration-capability (to depths ~1.5-2 km), time domain electromagnetic (TDEM) geophysical method, named Cycle-5M, for hydrological research; (2) to delineate the spatial distribution of fresh, brackish and saline groundwater bodies, as well as brine, beneath the Judea Desert, Israel. The study results show that both intentions were successful.

The study was conducted at 21 locations at the Judea desert plateau (Fig. 1), where fresh groundwater flows through the upper aquifers from the replenishment area at the Judea Mountains toward the Dead Sea springs. In deeper aquifers brackish and saline groundwater bodies exist, originated from lakes and lagoons, existed at the Dead Sea Rift valley during the Pleistocene and Pliocene, respectively. It was found that within carbonate formations, fresh groundwater (C<103 ppm Total Dissolved Solids, TDS) is characterized by a resistivity of more than 15 ohm-m; brackish groundwater (103A fresh/brackish groundwater interface was detected at a depth of 500-1000 m below land surface throughout the study area (Fig. 2). A brackish/saline groundwater interface was identified only adjacent to the eastern margins of the plateau (due to exploration limits), and apparently represents a continuation of the same interface detected at the Dead Sea coastal aquifer. The thickness of fresh groundwater lens was delineated (Fig. 3).