PhD: Rapid regional mapping of fresh-saline groundwater distributions and hydrogeological properties using airborne geophysics

Within the Water Nexus scientific program, project 1.1 comprises three parts with a combined aim to manage fresh-saline groundwater resources regionally through the development of innovative techniques and models. This PhD (part 1.1.1) aims to map the regional distribution and volume of fresh and saline water in coastal areas. Understanding the fresh-saline distribution of groundwater is essential for sustainable (ground) water management. This is usually monitored using expensive and time consuming ground-based techniques which offer limited spatial resolution, affecting its applicability from a water management point of view. For regional scale mapping, airborne electromagnetic monitoring (AEM) offers a rapid and cheaper alternative to these conventional methods.

AEM methods work by transmitting and receiving electrical signals from the subsurface using an instrument towed beneath a helicopter called a bird. These signals produce currents, which are in turn detected by receivers. As a result, the system detects electrical conductivity within the subsurface – which in the case of hydrogeological studies, relates primarily (but not exclusively) to clay content of the lithology and/or the salinity of the groundwater.

Using data-assimilation techniques, this research aims to combine numerical modelling, airborne electromagnetic monitoring and conventional in-situ observations to effectively map the regional fresh-saline distribution and hydrogeological properties over the three study areas. The results of this research will provide useful guidelines, highlighting the usefulness of AEM techniques. Furthermore, through investigating the use of inversion and numerical modelling techniques, potential improvements in the use of AEM in characterising fresh groundwater resources in hydrogeological settings is investigated.

The electromagnetic data for this PhD derives from three research areas:

Location

Survey Type

Survey Date

Project Name

Research Partners

Zeeland, the Netherlands

Airborne

2014 – 2015

FRESHEM

Deltares, BGR, TNO

Flanders coastal zone, Belgium

Airborne

2017

TBC

Deltares, SkyTEM, Universiteit Gent, TNO, Inagro, De Watergroep

Mekong Delta, Vietnam

Ground

2016 - 2017

Rise and Fall

Deltares, Utrecht University (UU), Can Tho University, Vietnam, HydroGeophysics Group – Aarhus University

 

As the geology and fresh-saline groundwater distribution of Zeeland is well understood, AEM mapping techniques will be tested here first. The results of this will be subsequently applied to the (relative) data-poor areas in the Mekong Delta and Flanders.