Airborne electromagnetics for groundwater salinity mapping: case studies of coastal and inland salinisation from around the world

Groundwater salinisation is a serious problem affecting numerous areas of the world, both in coastal and interior regions. Airborne electromagnetics (AEM) is a very effective tool for mapping hydrogeology, and therefore for managing salinisation related issues at large scale. We present here a representative collection of case studies from areas around the world describing its potential. In Banda Aceh, the applied methodology proved that the shallow aquifers did not suffer any long term effect from the tsunami of 2004. In Yucatan, it mapped the network of caves of that remote coastal Karstic environment. Along the south Australian coast, it provided hydrogeological insight from areas of a National Park which were interdicted to boreholes. In Venice AEM was used to add a great amount of data from the bottom of the lagoon, and to better understand the surface water-ground water interaction, in an area where geophysical measurements are particularly challenging, and borehole very sparse and, potentially, dangerous. Along the Murray Darling corridor, in south Australia, the technique was crucial in refining the understanding of dry land salinisation processes, and in trying to manage it. In the Okawango delta, it helped studying the surface water groundwater interactions, and the processes that keep the latter fresh while salt islands grow.