Doctoral defence: Magdaleena Männik „Groundwater vulnerability assessment in confined aquifers: modifying the DRASTIC method for aquifers covered by Quaternary deposits“

On the 21st of November at 12.15 Magdaleena Männik will defend her doctoral thesis „Groundwater vulnerability assessment in confined aquifers: modifying the DRASTIC method for aquifers covered by Quaternary deposits“ for obtaining the degree of Doctor of Philosophy (in Geology).

Supervisors:
Associate Professor Enn Karro, University of Tartu
Andres Marandi, Geological Survey of Estonia
Professor Alar Rosentau, University of Tartu

Opponent:
Professor Christoph Neukum, Federal Institute for Geosciences and Natural Resources (Germany)

Summary

Groundwater is a vital natural resource that supports ecosystems and agriculture and serves as the primary source of drinking water for nearly half of the world’s human population. However, it is vulnerable to contamination from intensive agriculture, urbanisation, and industrial areas. Assessing groundwater protection is particularly challenging in settings where aquifers are confined and overlain by a complex layer of Quaternary sediments.

The aim of this doctoral thesis is to adapt the internationally recognised DRASTIC method to better suit the hydrogeological conditions of Estonia and other formerly glaciated regions. By modifying three key parameters (depth to water, Quaternary sediment type and thickness), a new method was developed that accounts for the protective role of the Quaternary deposits and the effect of hydraulic pressure in confined aquifers.

The method was tested in three case study areas in Estonia and in a transboundary region between Estonia and Latvia. The results showed that the type and thickness of the sediment cover are critical in determining groundwater protection. The new approach produced more reliable results than the manually compiled vulnerability maps previously used in Estonia and proved suitable for cross-border applications. Land use was also included in the assessment, helping to identify areas where low natural protection combined with intensive human activity leads to elevated pollution risk.

The findings demonstrate that the new method is particularly effective for assessing the vulnerability of two-layer systems, where the main aquifer is covered by a variable Quaternary cover. This dissertation provides a practical, science-based, and up-to-date solution that can replace Estonia’s current manual vulnerability mapping approach. The new method enables faster and more objective assessments and supports the protection of clean drinking water and the sustainable management of groundwater resources.