MODELING OF HYDROLOGICAL DRAINAGE AND SEDIMENT YIELD PATTERNS IN MARCELLUS SHALE DRILLING REGION IN CENTRAL PENNSYLVANIA USING SWAT AND TOPOGRAPHIC WETNESS INDEX

With the ongoing Marcellus Shale gas-well drilling activities in central Pennsylvania, Lock Haven University’s Water and Soil Resources Lab has partnered with the Susquehanna River Basin Commission (SRBC) to determine if earth disturbances due to Unconventional Natural Gas Development (UNGD) alter the hydrological drainage pattern of surface runoff and sediment yield to the receiving streams. There is an increased concern that sediment yield increases due to development of Marcellus Shale infrastructures and modifications of existing dirt and gravel roads. Two watersheds, namely the Marsh Creek and Baker Run, in Centre and Clinton Counties, PA were selected to assess impacts of Marcellus Shale infrastructures on surface run-off and sediment yield.

The Soil and Water Assessment Tool (SWAT) and Topographic Assessment using DEM (TauDEM) software were used to model topographic wetness index (TWI), flow accumulation and modification patterns, hydrologic response units (HRU), and sediment yield patterns. High resolution LiDAR data, land-use raster, and soil data were used to create TWI and HRU for the selected watersheds. The TWI was blended with the digitized earth disturbance features related to Marcellus activities to determine modification in drainage patterns.

Numerous conclusions have been reached regarding the earth disturbances due to UNGD. The preliminary observations of the TWI indicate modification of the hydrologic drainage patterns due to construction of Marcellus infrastructures. The density of unpaved roads is greater (2.19 km/km²) in sub-basins that contain Marcellus activities, as compared to the ones without Marcellus activities (0.81 km/km² in Baker Run and 0.42 km/km² in Marsh Creek). The SWAT model indicates that three out of six sub-basins in Baker Run watershed that contain Marcellus Shale infrastructures are located in areas of high surface discharge, indicating the potential to create high sediment yield to receiving streams. The TWI and SWAT models validate that Marcellus infrastructures pass through topographically wet areas and multiple land-use patterns, some of which are environmentally sensitive.