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

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 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 transferability of data. Assessments of the tracts reflected the small storage of water in underlying rocks and corresponding limited 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 to some degree of 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. Hydrologic assessments of the tracts, based on limited verification data, proved to be reasonably accurate. Almost all ground-water verification data fall within estimated ranges and the remainder are close. Similarly, almost all surface-water quality data obtained fall within estimated rangesmore » based on variations in discharge, and most of the remainder are close. Impacts that will result from future mining in tracts are defined. Methodology used to estimate future impacts on surface-water quality is described with examples. 9 references.« less