This report, prepared in cooperation with the Pennsyl-vania Department of Environmental Protection (PaDEP), the Eastern Pennsylvania Coalition for Abandoned Mine Reclama-tion, and the Dauphin County Conservation District, provides estimates of water budgets and groundwater volumes stored in abandoned underground mines in the Western Middle Anthra-cite Coalfield, which encompasses an area of 120 square miles in eastern Pennsylvania. The estimates are based on prelimi-nary simulations using a groundwater-flow model and an associated geographic information system that integrates data on the mining features, hydrogeology, and streamflow in the study area. The Mahanoy and Shamokin Creek Basins were the focus of the study because these basins exhibit extensive hydrologic effects and water-quality degradation from the abandoned mines in their headwaters in the Western Middle Anthracite Coalfield. Proposed groundwater withdrawals from the flooded parts of the mines and stream-channel modifi-cations in selected areas have the potential for altering the distribution of groundwater and the interaction between the groundwater and streams in the area.