Developing Recharge Reduction Strategies in the Tintinara Area of South Australia Using Resolve Frequency Domain Helicopter Electromagnetic Data

In the Tintinara area, located south-east South Australia, airborne geophysics was recognized as having potential to provide valuable biophysical data relevant to the management of irrigation development and groundwater recharge reduction in the area. The groundwater of the area sustains irrigation and other dryland agriculture. However the lifetime of this resource is limited by the leaching of salt that has accumulated in the soil prior to land clearing and agricultural development. For some areas, the groundwater may be saline and unusable for irrigation within ten to twenty years. The presence or absence of a near surface clay unit can have an important influence on the rate and timing of this deterioration by slowing recharge. Forward modelling suggested that a frequency domain helicopter electromagnetic (HEM) system could map spatial variability associated with this unit. A survey was conducted using the RESOLVE HEM system and demonstrated that, through the use of a constrained inversion approach, this unit could be mapped. This was confirmed with shallow drilling. We have generated a product, namely clay thickness, which is now being used as an input into a hydrogeological model to help predict recharge rates and influence management decisions in the area.