Investigating Heterogeneous Costal Aquifer Using Magnetic Resonance Tomography and TDEM

Abstract

Magnetic Resonance Tomography (MRT) and Time Domain Electromagnetic (TDEM) methods were applied to investigate a costal aquifer in the Dead Sea area of Israel. The subsurface in this area is highly heterogeneous and composed of intercalated sand and clay layers over a salt rock, which is partly karstified. Groundwater is very saline, with a chloride concentration of 100-225 g/l. Variation of the water salinity is poorly known. TDEM is an efficient tool for locating electrically conductive targets like saline water, but it is also sensitive to the porosity of rocks. MRT, however, is sensitive primary to groundwater volume but also to lithological variations in the subsurface (through the relaxation time T1). We used MRT for a 3D imaging of the water content in the subsurface and 2D mapping of the T1. 3D distribution of the electrical resistivity was obtained using interpolation of 1D TDEM results. We show that joint use of the MRT and TDEM enables us to resolve the aquifer and to demonstrate that the salinity of water in the investigated area is fairly constant.