Assessment of hydrologic conditions in potential coal-lease tracts in the Warrior coal field, Alabama

Abstract

Assessing the hydrology of potential Federal coal-lease tracts, because of their dissemination and limited data, requires some predictive capability. Four tracts assessed were located in the outcrop of three coal groups and of other relatively impermeable rocks in the Pottsville Formation. Physical settings of the tracts and most other areas in the Warrior coal field are similar. This results in similar ground-water and surface-water characteristics, in similar impacts resulting from surface coal mining, and in maximizing the transfer-ability of data. Assessments of the tracts reflected the small storage of water in underlying rocks and corresponding low yields to wells and to the base flow of streams. Ground water and surface water in undisturbed areas are generally of good quality. Some subbasins in the tracts have already been impacted by mining. Estimates of streamflow characteristics and the availability and quality of ground water in the tracts were made using available methodology , or assessments based on local and regional data. Estimates of the degree mineralization of surface-water were made using methodology developed from other coal hydrology work. Climatic, physiographic, hydrologic, and land-use data were analyzed by regressions to derive relations for assessing water quality in streams draining mined and unmined areas. In this approach, an equation was derived to estimate specific conductance. Additional equations, based on relations between specific conductance and other constituents, allow estimates of mine drainage indicators such as hardness, dissolved solids, and sulfate. Hydrologic assessments of the tracts, based on limited verification data, proved to be reasonably accurate. (USGS)