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Estimating subsurface porosity and salt loads using airborne geophysical data
Author(s) -
LeyCooper Yusen,
Macnae James,
Tweed Sarah
Publication year - 2008
Publication title -
near surface geophysics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.639
H-Index - 39
eISSN - 1873-0604
pISSN - 1569-4445
DOI - 10.3997/1873-0604.2007029
Subject(s) - groundwater , aquifer , geology , hydrogeology , porosity , borehole , hydraulic conductivity , electromagnetics , hydrology (agriculture) , soil science , soil water , geotechnical engineering , engineering , electronic engineering
We aim to map dissolved salts in aquifers which, with rising water tables, are a threat to fresh water resources and ecosystem health. Interpolated groundwater electrical conductivity (EC) maps from borehole measurements are combined with spatially detailed bulk electrical conductivities estimated from airborne electromagnetics to provide, through Archie’s law, a detailed prediction of subsurface porosity and total dissolved salt load of any near‐surface aquifer. This technique quantitatively integrates airborne electromagnetic and groundwater measurements of EC to provide the subsurface detail necessary for hydraulic properties. The process has been applied in Australia’s Murray River Basin, where the presence of salt is a threat to agriculture and fresh water supplies. Porosity predictions range between 1% and 50% and are spatially consistent with known geology, dissolved salt loads are estimated to be between 100 and 4000 tonnes per hectare. The predictions are yet to be compared to in‐situ measurements but if proven, will be a useful tool when in‐situ porosity is under‐sampled or is not available.