Porosity and Dissolved Salt Load Estimation from Geophysical Airborne Em and Borehole EC

Dissolved salt in aquifers can be a hazard to fresh water resources. Interpolated grid maps at the depth of the aquifer, derived from EC measurements on borehole water samples, can be combined with more detailed bulk electrical conductivities from airborne electromagnetics to provide detailed predictions of subsurface porosity and total dissolved salt load. The calculated porosity and salt load are in fact maximum estimate values since a resistive host matrix is assumed. The technique has been applied to vertically distinct aquifers in two different areas of the salt-threatened Murray-Darling basin in Australia. This technique may provide extensive information on the hydraulic properties of aquifers, has important implications for quantitative hydrological models, particularly in estimations of sustainable groundwater use, and timeframes for saline groundwater migration