ASSESSMENT OF THE NEAR-SURFACE HYDROLOGICAL CHARACTERISTICS OF 12-YEAR OLD GRASS AND FORESTED SITES ON A RECLAIMED COAL SURFACE MINE IN SOUTHWESTERN, VIRGINIA

Infiltration characteristics and near-surface patterns of water movement through reclaimed surface coal mines are largely unknown. These two processes influence the physical hydrologic behavior and chemical composition of waters discharging from surface coal mines in Central Appalachia. The objective of this study was to improve understanding of how near-surface water movement is influenced by vegetative cover type on mine sites. Tension infiltration and Brilliant Blue FCF dye staining tests were conducted on a 12 year old reclaimed surface mine site in Southwestern Virginia. The two study plots had similar ages, slopes, spoil types and initial soil moisture conditions, enabling the comparison of a site reclaimed with non-native grasses to one re-vegetated with native trees. Infiltration rates ranged from 4cm hr^-1 to 97 cm hr^-1 in the grass plot and from 5cm hr^-1 to 68 cm hr^-1 in the forested plot, with the infiltration rates in the forested plot greater than the grass plot on average. The large range in infiltration rates indicates the heterogeneous surface and subsurface, which consists of areas with small particle sizes and loamy soil, as well as areas with large rock fragments and voids. The hydraulic conductivities (k) averaged 0.0013 and 0.0017 cm s^-1 for the grass and forested plots, respectively. Dye staining showed differing patterns of subsurface water movement for the two plots, with the types of flow including both matrix flow and preferential flow. Initial results indicate that reclaiming with native trees may increase soil infiltration rates relative to conventional reclamation practices, thus decreasing the potential runoff and stormflow response of streams impacted by surface coal mining.