Simulation of Ground‐Water Flow in a Mined Watershed in Eastern Ohio^a

Abstract

A 43‐acre watershed in Muskingum County, Ohio, was studied to determine the hydrologic consequences of strip mining for coal. A quantitative description of the effects on the ground‐water flow components of the hydrologic system has been obtained using digital models. The premining watershed was characterized by nearly flat‐lying sedimentary rocks of the Pennsylvanian System. Underclay beneath the two major coal beds formed bases for perched zones, creating three separate aquifers. Recharge to the ground‐water system occurred mainly by percolation of precipitation. Most of the discharge from the top and middle aquifers occurred by downward leakage to the underlying aquifers. A smaller amount of discharge occurred as springflow or streamflow near the intersections of the underclays and land surface. Mining has destroyed the top aquifer, and has replaced the bedrock by spoil material. Water levels in the spoils are at a much lower altitude than existed in the premining top aquifer because of a combination of (1) a larger hydraulic conductivity, (2) areal variations of the hydraulic characteristics of the confining bed, and (3) a slower rate of recharge from precipitation caused by removal of vegetation and soil compaction. Covering of previously exposed portions of the middle aquifer and a lower hydraulic head in the spoils has allowed less recharge to the middle aquifer. Additional flow is induced across the western boundary of the watershed and has reduced the outflow across the eastern boundary. Discharge from the middle aquifer as downward leakage and streamflow is less than before mining.

Hydrologic Effects of Surface Coal Mining in Appalachia (U.S.)

“…Researchers have found that Appalachian mine soil infiltration is influenced by factors similar to those influencing infiltration on native soils such as presence of high soil densities constraining infiltration capacity. Working in an Ohio watershed that was mined and reclaimed using native soil cover and soil compaction, Weiss and Razem () found increased rainfall runoff and slower groundwater recharge despite an increase in subsurface hydraulic conductivity shortly after mining and reclamation, a result they attributed to surface soil compaction.…”

Geochemical response of acid groundwater to neutralization by alkaline recharge

“…The backfilling process in surface coal and base-metal mines may develop porous rubbly zones and tensionformed voids, permeable to both fluid and oxygen transport and either permanently or intermittently saturated at their base (Weiss and Razem, 1984;Schwartz and Crowe, 1985;Wunsch and Dinger, 1994). Acid-water flux from such aquifers may be influenced by the relative abundance of acid-producing and acid-neutralizing lithologies, morphology and size of pyrite grains, and the flux of oxygen transport into the spoil (Cathles and Apps, 1975;Renton et al, 1989;Ritchie, 1994).…”

Effects of surface coal mining and reclamation on the geohydrology of six small watersheds in West-Central Indiana

“…Hydrologic effects of surface coal mining and reclamation can be determined by study of watershed hydrology before mining began, during mining, and after reclamation (Curtis, 1973;Emerson, 1981;U.S. Department of Agriculture, Agricultural Research Service and Ohio State University, 1983;Weiss and Razem, 1984); by comparison of nearby mined and unmined watersheds (Corbett, 1965;Collier and others, 1970;Grubb and Ryder, 1972;Zogorski and others, 1981;Brabets, 1984); or by simulation (Wilson and Hamilton, 1978;Meadows and Blandford, 1983;Scott, 1984). For this study, effects of surface coal mining were identified by comparing hydrologic characteristics of mined and unreclaimed watersheds with those of unmined agricultural watersheds (Big Slough and Hooker Creek).…”