Ground geophysics for rapid location of buried valleys below high-value salt-affected land at Tammin, WA

Abstract

In the Tammin area, some of the most productive agricultural land is being lost to salinisation. A range of solutions designed to halt, and possibly reverse the process of salinisation of high-value land at Tammin has been proposed. One method to be trialled, is to lower the water table over a long time (years) by pumping water from the basal sands in buried valleys presumed to exist below the salt-affected land. However, before any such method can be assessed, the existence of the buried valleys needs to be rapidly and cost effectively demonstrated. The integrated use of gravity and transient electromagnetic methods has demonstrated the existence of a discrete buried valley below or adjacent to salt-affected land at Tammin. The axis of the buried valley does not follow the path of current surface drainage. The geophysical methods are shown to be effective and therefore an essential step in the planning and design process for developing an engineering method for salinity management at Tammin. It remains to drill and pump test the interpreted geophysical targets to assess the hydraulic characteristics of the groundwater system at Tammin.