Estonia's groundwater is a precious resource, vital for ecosystems, agriculture, and as a primary source of drinking water for its people. Protecting this resource is crucial, and a new tool developed by a geology doctoral student at the University of Tartu aims to do just that.
Groundwater vulnerability: A critical issue for Estonia's future.
Magdaleena Männik's dissertation focuses on assessing groundwater vulnerability across Estonia's diverse regions. With a history dating back to the last ice age, Estonia's landscape is a unique mix of surface deposits left by melting glaciers. These deposits, ranging from thick clay layers to thin sandy patches, play a crucial role in determining the vulnerability of groundwater to contamination.
"Some areas are naturally well-protected, while others are at higher risk. It's all about the interaction between the surface deposits and the bedrock," Männik explains.
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The current assessment guidelines, dating back to the 1980s, rely on manual mapping, which Männik argues is outdated and insufficient. Her customized version of the DRASTIC method, based on a geographic information system (GIS), offers a more transparent and realistic picture of groundwater protection.
"We need modern methods to ensure we're accurately identifying areas that need attention," she says.
But here's where it gets controversial: The internationally used DRASTIC method assumes deeper groundwater levels provide better natural protection. However, Estonia's hydrogeological conditions are more complex. The country primarily relies on confined aquifers, where groundwater vulnerability is influenced by the interaction between surface deposits and bedrock.
Männik's customized method helps distinguish between naturally well-protected areas and those at higher risk. It considers the impact of land use, especially intensive agriculture, which can break through natural barriers and pose a significant threat to groundwater quality.
"Diffuse pollution from agriculture is a major concern. Nitrates from fertilizers can easily seep into groundwater layers, especially in areas with thin surface deposits," she warns.
Her research highlights the Pandivere and Adavere–Põltsamaa regions as sensitive areas, where agriculture practices on thin surface deposits pose the highest risk. In contrast, areas like Pärnu, with thick varved clay layers, provide natural protection to groundwater.
Groundwater knows no borders, and Männik tested her method in a cross-border region between Estonia and Latvia. The geological conditions are similar on both sides, with confined aquifers covered by surface deposits that determine groundwater vulnerability.
"The customized DRASTIC method is applicable in Latvian conditions as well, offering a unified framework for assessing groundwater vulnerability across the border," Männik asserts.
This new approach has facilitated harmonized and science-based mapping, aiding both countries in their water management planning and decision-making. It identifies areas requiring monitoring, protection, and closer cross-border cooperation to ensure the sustainable use of drinking water resources.
Männik's doctoral thesis, "Groundwater vulnerability assessment in confined aquifers: modifying the DRASTIC method for aquifers covered by Quaternary deposits," was defended at the University of Tartu on November 21.
