17 January 2024
10:00 AM (Central Time)
In the Hydrogeophysics Group (HGG) at Aarhus University we have worked with geophysical methods in the hydro-domain for more than 30 years. Since the beginning of the 2000s we have had a strong focus on TEM methods beginning with the airborne SkyTEM system and later with ground-based systems, both stationary and towed (tTEM).
In the last few years, a new generation of TEM instruments has been developed, allowing for monitoring applications. Previously, any geophysical monitoring would typically be carried out with ERT type instruments as they could deliver the long-term stability and robustness required. With the newest TEM instruments, we now have a low-power, physically small, and non-drifting instrument that allows us to see relatively deep with a high and consistent accuracy.
We have installed several of these TEM monitoring instruments across Denmark, South Africa, and Senegal. I will discuss the main instrument design considerations allowing us to obtain a daily measurement over months or years. The potential applications for these kinds of instruments are many, but for now, we have focused on two main cases. Firstly, the monitoring of unconfined water tables where we can obtain decimeter accuracy at 10–40-meter depths. Secondly, we have monitored salinity changes in aquifers occurring over large depth ranges.
Besides showing some of the field cases, the presentation will also include discussions of instrument requirements and lessons learned in aiming to have continuous daily measurements with remotely installed instruments.
Anders Vest Christiansen
Anders Vest Christiansen is a Professor at Aarhus University, Denmark and head of the Hydrogeophysics Group. He received his PhD in 2003 within airborne TEM methods and inversion methodologies. Overall, his research focus still remains within these subjects. In the later years with an increased focus on the integration of various data types (e.g., geophysics with borehole info and hydrological observations) with the purpose of making objective and transparent processes that generate maps and other outputs that are in better agreement with the actual needs of the end-users.