Presenter: Yazeed van Wyk (will be on zoom for logistical reasons); it is advised that most of you still attend the in-person sessions with his supervisor(s) and other relevant people to ensure that the discussions and questions can be handled optimally.

Title: Combined use of environmental and artificial tracers to characterise the anthropogenically altered vadose zone and groundwater system 

Degree: PhD specialising in Hydrogeology (Department of Geology, University of Pretoria);

Supervisors: Prof Matthys Dippenaar; Prof Kai Witthueser; Dr Eunice Ubomba-Jaswa

Date: 16 October 2025

Time: 14:30-16:00 latest

Zoom: https://up-ac-za.zoom.us/j/95787352373?pwd=cRs13sdHNhuDDzbKQX0sImwpfqFRCY.1 (Meeting ID: 95787352373; Meeting passcode: 478558)

Venue: Mineral Sciences Building Room 4-22

RSVP and Details: https://forms.gle/ocWXdPcckijheTkMA (UP walk-ins are welcome)

Purpose: The purpose of this PhD defence is for the candidate to present his work to an audience that includes supervisors and examiners. It is not an examination but an opportunity to demonstrate the ability to defend the novelty and significance of the research. Attendance at this event is a celebration of the candidate’s achievement, having completed the written examination and met all other requirements for a PhD in Hydrogeology.

Short Abstract: Mining activities significantly alter vadose zone and fractured aquifer systems, impacting groundwater quality and sustainable mine closure. This study investigates groundwater flow and contaminant transport in a quarry near Pretoria, South Africa, using combined environmental (δ¹⁸O, δ²H, ³H) and artificial tracer (uranine, rhodamine WT) approaches. Field investigations revealed that blasting enhanced fracture connectivity, creating preferential flow pathways and seasonal variability in transport parameters. Analytical tracer modelling confirmed higher velocities and reduced retardation during wet conditions, highlighting the importance of seasonal calibration. An integrated conceptual site model (CSM) illustrates how quarrying has transformed groundwater pathways, providing critical insights for post-closure monitoring and groundwater protection strategies.

Yazeed van Wyk is a groundwater hydrology professional with a PhD in Hydrogeology from the University of Pretoria and over 15 years of experience in the water sector. He currently manages the groundwater hydrology portfolio at the Water Research Commission, under the Water Availability thematic area within the Research and Development branch. Dr. van Wyk’s expertise lies in the use of isotopes and artificial tracers for the study and management of both vadose zone and groundwater systems. He has managed and contributed to numerous research, development, and innovation projects and publications in groundwater hydrology, focusing on sustainable water resource management and understanding anthropogenic impacts on groundwater systems.

He is a Fellow of the Water Institute of Southern Africa, Treasurer of the Groundwater Division of the Geological Society of South Africa, and serves on the Scientific Committee of the UNESCO China-Africa Water Association. He is also a member of the International Association of Hydrogeologists, the South African National Commission (SANC) for UNESCO Youth Task Team, and acts as the South African national counterpart to the International Atomic Energy Agency (IAEA).