Gamma-ray spectrometric datasets are useful in salinity studies by providing information on the distribution of soil and other regolith materials. Soil characteristics predicted from gamma-ray imagery (Pracilio et al. 2002) were used in Western Australia to map areas of deep drainage beneath cropped farmland. Areas of deep drainage are a major source of groundwater recharge that contributes to rising water tables and salinity. Wilford et al. (2001) used slope thresholds and residual analysis techniques to separate gamma-ray responses relating to soil/regolith from bedrock materials. Areas of relatively thick clay-rich regolith with associated higher salt stores were identified using this approach. A combination of gamma-ray thematic maps and terrain indices were then used to predict areas of likely saline discharge (see Bethrungra 3D interactive model).
The accumulation of radium (226Ra) in groundwaters (Giblin and Dickson 1983) and radon gas (222Rn) in soils (Grasty 1994) have the potential to be useful in groundwater investigations. Radium and Rn are short-lived members of the Th and U decay series chains. Radium mobility and Rn gas production can be a source of disequilibrium in both series. Radium is mobile in groundwaters, particularly saline groundwater. Dickson (1985) and Dickson and Giblin (1987) detected U anomalies associated with elevated Ra associated with saline seepages and waterlogged areas at the foot of sandstone escarpments.