The Murchison palaeovalley (MPV) system is an arid basin covering an area of approximately 129 000 Km2 that was identified as one of six key priority project areas across Western Australia that required research to identify water sources to support population growth, agriculture and mining. The MPV project supports the WA Government strategic focus to assess and provide advice on groundwater availability to meet current and future demand. An airborne electromagnetic (AEM) survey was flown across the upper Murchison River catchment in early 2015. The survey collected 14,022 line kilometers of data, mapping approximately 52,000 square kilometres of the MPV system. The AEM survey data has been evaluated in association with geological and groundwater quality information sourced from more than 2000 existing boreholes across the MPV project area.
The Department of Water worked in collaboration with expert CSIRO geophysicists to process the AEM information using techniques that were developed specifically for this project.
The initial interpretation of these data indicates a wide range of saturated sediments with the value and useability of the groundwater dependent upon quality. Borehole information together with historic and observational data indicates that the best quality groundwater to be associated with calcrete outcrops located in the upper reaches of catchments. The calcrete forms transmissive horizons that enhance rainfall infiltration and groundwater storage.
The AEM data was processed with data including radiometrics and 1:250 000 geological mapping to identify near surface calcium carbonate (calcrete) deposits. A field evaluation project initiated to verify the accuracy of the mapped data showed these areas to have a complex nature and an exceedingly varied depositional history. The field evaluation project has improved mapping techniques and provides a means to better understand calcrete formation.
This paper will give an overview of the results of the field mapped versus remote sensed calcrete mapping.