Integration of airborne transient electromagnetic models with ground geophysics and borehole data for groundwater mapping in Hawkes Bay region, New Zealand

As part of the Hawke's Bay 3D Aquifer Mapping Project (3DAMP), airborne electromagnetic data have been collected over several basins. The project was a three-year initiative (2019 - 2022) jointly funded by the Provincial Growth Fund (Knoa Regional Economic Development & Investment Unit), Hawke's Bay Regional Council (HBRC) and GNS Science (GNS). The object of the study is to improve the hydrogeological model of the area using a resistivity model that extends to 300 m depth. The model was generated from an airborne TEM (SkyTEM) survey that covered the region at a line spacing of 170 - 250 m. A total of 7780 line-km was flown in a period of 4 weeks. Supporting data includes ground-based geophysical surveys (TEM, resistivity, and seismic reflection lines), and detailed geological data from a set of research boreholes. A total of 6800 boreholes exist in the catchments but the majority are less than 30 m deep. A set of 30 deeper boreholes across the area with more detailed geological information provide valuable control on the SkyTEM processing and modelling. The integration of a 3D model developed from the inversion of the SkyTEM data and ground geophysics data, displays the geometry of the fluvial systems (gravel), marine incursions (silt and clay), and complex faulting that affects the deposition of the sedimentary units. Work is ongoing to develop models of aquifer potential based on hydrogeological facies that will improve the understanding of the groundwater system.