Rapid Mapping of Hydrological Systems in Tanzania Using a Towed Transient Electromagnetic System

Abstract

Limited knowledge of local groundwater systems often results in the failure of boreholes to yield water of the required quantity and quality. This is particularly problematic in the developing world, where financial resources are often limited, and failed wells represent a significant financial burden. To enhance understanding of local hydrological systems, noninvasive geophysical methods can aid the understanding of hydrogeological structures and identification of groundwater sources needed to optimize siting of wells. Here, we highlight the utility of a relatively new towed-transient electromagnetic system, called tTEM. This system is a rapidly deployable mobile geophysical method well-suited to cost-efficient characterization of local-to-regional groundwater systems. Results from tTEM surveys conducted in two refugee camps and several host communities in western Tanzania demonstrate the capability of the method to characterize shallow aquifer systems with high lateral and vertical resolution, with data collection typically exceeding 15 to 20 line-kilometers (km) per day. This work focuses on tTEM's ability to provide semiquantitative insights into regional hydrogeological settings when supporting data required for more rigorous interpretation/modeling is lacking. The system provided useful data within communities with low density of electrification and near buildings with metal roofs and walls. tTEM-derived resistivity profiles were correlated with limited local borehole lithologic information to develop conceptual models of the local groundwater systems. These models were used to successfully guide the siting of a production well and to identify future drilling targets in the refugee camps and surrounding communities.

Performance of light fixed‐wing airborne time‐domain electromagnetic system for mapping the near‐surface cover layer in an alluvial plain context: A numerical study

“…Closer resistivity values between lithologies would result in much lower resolution capabilities, and new specific sensitivity studies following the same frame will have to be carried out in order to answer other geological contexts. For metric or even higher resolution of the cover layer, only ground‐based surveys are able to provide information at such a small scale, such as the recent towed tTEM system (Grombacher et al., 2022), despite the fact that authorization for accessing agricultural parcels cannot be obtained depending on the period.…”

Evaluating the impact of correlated noise for time‐lapse transient electromagnetic (TEM) monitoring studies

“…Early TEM applications primarily focused on mineral prospecting; however, hardware and data processing developments have facilitated the resolution of subtle resistivity patterns related to hydrogeology (e.g., Auken et al., 2017; Chongo et al., 2015; Grombacher et al., 2022; Kalisperi et al., 2018). Although most hydrogeological TEM applications utilize single surveys to characterize subsurface spatial variability, there is substantial potential for TEM to resolve temporal changes.…”

TEM Strata Inversion Imaging with IP Effect Based on Enhanced GCN by Extracting Long-Dependency Features

“…This non-intrusive geophysical method, known as transient electromagnetic (TEM) detection, is extensively employed for subsurface imaging and exploration [5][6][7], particularly for low-resistivity target areas [8]. It finds broad applications in environmental monitoring [9,10], source exploration [11,12], and geological studies [13,14].…”