Work

Groundwater flow regimes and intrinsic vulnerability in a fractured bedrock aquifer: insights from hydrochemistry, isotopes, geophysics, and groundwater age

Year: 2026

Type: article

Abstract: Intrinsic vulnerability in fractured bedrock aquifers is commonly evaluated using index-based approaches, yet these methods often underestimate the role of flow system architecture, recharge mechanisms, and groundwater renewal in controlling contaminant susceptibility. In structurally complex aquifers, vulnerability patterns are strongly controlled by heterogeneous flow paths and residence time distributions, which are not adequately represented by static approaches. This study integrates hydrochemistry, environmental isotopes (δ 18 O, δ 2 H, 87 Sr/ 86 Sr), tritium-based groundwater age modeling, multivariate statistical analysis, and geophysical investigations to constrain groundwater flow systems in a fractured bedrock aquifer in the Boeun region, Korea. Integration of these independent datasets reveals three distinct groundwater flow regimes: (i) a laterally dominated shallow system with strong surface connectivity, (ii) a vertically stratified mountain front recharge system with fracture-controlled deep circulation, and (iii) a rapidly renewed shallow system characterized by short residence times and diffuse recharge. The identified flow regimes provide a processed-based framework for interpreting intrinsic vulnerability. Despite groundwater quality index values indicating excellent water quality at present, DRASTIC results show moderate to high vulnerability associated with rapid recharge and structurally connected flow paths. This contrast demonstrates that intrinsic vulnerability is primarily controlled by recharge processes, groundwater flow systems, and renewal dynamics, rather than by static hydrogeological parameters alone. These findings highlight the importance of incorporating groundwater renewal dynamics, residence time structure, and flow system heterogeneity into vulnerability assessments of fractured aquifers

Source: Journal of Hydrology

DOI: 10.1016/j.jhydrol.2026.136072