Mapping a Fluvial Aquifer in New Zealand Using Airborne Tem, Seismic, and Electrical Soundings

Summary A SkyTEM airborne survey has been flown over 1820 km2 of an area of intense agriculture in Hawkes Bay region of New Zealand. The survey is designed to map the characteristics of a coastal fluvial aquifer and support the management of groundwater resources. Processing the data from a 590 km2 subset of the survey, adjacent three urban centres, has been helped by using ground-based geophysical data. These data include ground-TEM, DC resistivity soundings, and borehole geophysical logs. Seismic reflection data across the region provide constraints on the deeper sections of the aquifer system (200 – 500 m). One of the key aims of the study is to map the variability of the surface geological strata that in places are a recharge zone and in other places a confining layer for the aquifer. The SkyTEM data have a spatial coverage (170 m line spacing and 20–30 m station spacing) that enables these units to be mapped in more detail than is possible with the current boreholes and ground geophysical data. In places the ground-based data provide valuable support for constraining the shallow SkyTEM models where data can be missing and deep parts of the SkyTEM model where the resolution is low.