Porosity and Salt Load Prediction from Airborne EM and Borehole EC

Abstract

Dissolved salt in aquifers is a potential threat to fresh water resources and the environment. Interpolated grid maps at aquifer depths, derived from borehole EC measurements on water samples, are combined with more detailed bulk electrical conductivities from airborne electromagnetics to provide detailed estimates of total dissolved salt load and subsurface porosity values. A resistive host matrix assumption implies that our calculated porosity and salt load values are maximum values. This mapping technique is a large area coverage remote senor method which has been tested in different areas of the salt-threatened Murray-Darling basin. This technique provides extensive information on the hydraulic properties of aquifers, important for quantitative hydrology.