Environmental Legacy of Coal Mining: Ongoing Water Contamination in El Bierzo and Laciana
The environmental footprint of coal mining continues to affect the watersheds of El Bierzo and Laciana decades after the mines closed. A recent study conducted by the University of Leon has identified significant contamination in rivers, streams, springs and wells across these regions primarily attributed to former mining operations. This ongoing pollution is characterised by the presence of acidic waters sulphates and heavy metals that threaten both ecosystems and water quality for human consumption.
Research results based on sampling at ninety-two locations over a three thousand four hundred fifty square kilometre area emphasise the long-term impacts of abandoned mining sites. The investigation presented at the GeoLaciana 2026 conference was carried out between October 2020 and April 2022 collecting data from surface and underground waters to assess contamination levels. Findings reveal that the closure of coal mines has inadvertently led to acid drainage from waste heaps and mine shafts discharging sulphates and toxic metals into the aquatic environment. These fluids gradually reach rivers and streams with some infiltrating aquifers over time.
The study highlights that the affected catchments especially those with historic mining activities such as the Tremor river basin and its tributaries like the Silva stream and Rodrigatos exhibit elevated levels of sulphates and heavy metals. These elevated contaminants sometimes surpass regulatory limits established for drinking water including aluminium iron manganese nickel arsenic and lead. Although groundwater samples show less contamination than surface waters indications point to an increasing trend of subsurface pollution due to ongoing infiltration.
Natural attenuation mechanisms such as dilution by clean water inflows and geochemical processes have temporarily reduced some pollutant concentrations. However the study warns that acid drainage from abandoned mines remains an unchecked source of environmental pollution continuously releasing contaminants into the water network. This persistent leaching raises serious concerns about long-term water quality and ecosystem health.
Experts advocate for urgent further research and regular monitoring. Specifically they emphasise the need to update inventories of waste heaps and lixiviation sites deepen understanding of the relationship between abandoned galleries and water bodies and develop targeted strategies to mitigate ongoing contamination. The findings underline a critical reality despite the end of active mining the environmental impacts of coal extraction linger necessitating comprehensive remedial actions to restore water quality and protect regional ecosystems for future generations.