Hydrogeological Complexity and Ground Fissures in the Amyntaio Basin: The Role of Tectonics and Anthropogenic Interventions

This study evaluates the complex hydrogeological conditions of the Amyntaio Basin by synthesizing historical data with updated 2021 piezometric measurements. The region’s geological framework is defined by intense neotectonic activity and lithological anisotropy, resulting in a system of overlapping granular aquifers—unconfined, leaky, or confined—that exhibit complex hydraulic behaviors.

The Groundwater aquifers of Amyntaio-Florina and Perdikka-Filota are categorized as having "Poor" quantitative status under EU Water Framework Directive criteria. While industrial dewatering associated with Public Power Corporation Lignite Mining has decreased since 2018 and stopped in may 2020, the basin remains under significant stress due to sustained abstractions for irrigation and municipal supply. The research indicates that the basin's response deviates from classical porous media models due to the presence of hydraulic boundaries and fault-controlled lateral recharges.

A critical re-evaluation of the monitoring network revealed that historical data (pre-2021) often lacked the resolution to distinguish between distinct aquifer horizons. The integration of deep-seated piezometers (>200m) into the 2021 network facilitated a high-fidelity mapping of the piezometric surface. Findings indicate that the hydraulic influence of mine dewatering is characterized by a high hydraulic gradient but a limited spatial radius, typically restricted to a zone of 500–800m from the mine’s crest.

The investigation into ground fissures and land subsidence in the settlements of Valtonera, Fanos, and Rodonas suggests a multi-causal mechanism, almost independent of mining activities:

• Lithological Vulnerability: Settlements are founded on Holocene deposits with poor geomechanical properties.
• Piezometric Drawdown: Localized intensive irrigation creates discrete cones of depression, often deeper than those observed near the industrial fronts.
• Peat Oxidation and Consolidation: Following the historical reclamation of the Chimaditida marsh (1960s), the aeration of organic-rich horizons initiated biochemical oxidation. This process, coupled with the loss of buoyancy in the drained peat layers, has resulted in sustained, long-term volumetric shrinkage and surface deformation.
• Tectonic Control: Major fault systems (e.g., Petron-Sklithro) act as planes of weakness, facilitating differential subsidence and aseismic creep.

In conclusion, the environmental degradation in the Amyntaio Basin is a long-term process governed by a synergy of tectonic constraints and initiated by marsh drainage and century-long anthropogenic interventions. The limited recovery potential of the aquifers, particularly in zones distal to the primary recharge points (Sklithro and Rodonas streams), necessitates a specialized management strategy that accounts for the basin's compartmentalized hydraulic behavior.