USGS Mapped Pennsylvania Mine Water Storage

Researchers quantified water volumes within the Western Middle Anthracite Coalfield to better understand basin hydrology.

Updated on Oct. 1, 2026 in Geography

Isometric editorial illustration of subterranean coal mine geological strata with flooded galleries, depicting regional hydrologic infrastructure. — The U.S. Geological Survey mapped underground water storage in abandoned Pennsylvania coal mines, estimating they contain up to 220 billion gallons. AI Illustration. Upload story photo >

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Should abandoned industrial mine sites be utilized as managed water reservoirs for your community?

The U.S. Geological Survey has mapped underground water storage in abandoned coal mines across a 120-square-mile area in Pennsylvania. The research estimates that these abandoned workings hold between 60 billion and 220 billion gallons of water.

Why it matters

Abandoned coal mines have significantly affected local streamflow and water quality throughout the region. Understanding these subterranean reservoirs is essential for managing the water systems connected to the Mahanoy and Shamokin Creek basins.

The study utilized a 3D groundwater-flow model to estimate volumes based on bulk porosity assumptions of 11% and 40% for the coal seams. The maximum estimate of 220 billion gallons is equivalent to 675,000 acre-feet of water.

The players

U.S. Geological Survey

A scientific agency that provides reliable data on the earth, its natural resources, and the hazards that threaten it.

The details

Researchers mapped the mines by integrating 3D groundwater-flow models with geographic information systems, which are software frameworks for gathering and analyzing spatial data. The team identified underground boundaries using historical mine maps, known discharge points, and groundwater-level measurements. By dividing the workings into multicolliery units, the model was calibrated against stream baseflow data to account for interactions between mine pools and surface water.

October 1, 2026: The U.S. Geological Survey published the research report.

The Tech Race

This study aligns with established U.S. Geological Survey water-resource assessment protocols for complex mining landscapes. It represents a shift from anecdotal observation of mine-pool impact to standardized, model-based quantification of subsurface water resources.

Residents in Schuylkill, Columbia, and Northumberland counties may see improved water management strategies as authorities utilize this data to track streamflow. The findings provide a foundation for future infrastructure projects that must account for potential groundwater interactions.

The takeaway

The study highlights the massive scale of water accumulation in legacy mining infrastructure, estimating volumes as high as 220 billion gallons. Researchers now advocate for continuous monitoring of discharge rates and tracer studies to validate these findings.