DETERMINATION OF THE LOCATION OF THE GROUNDWATER DIVIDE AND NATURE OF GROUNDWATER FLOW PATHS WITHIN A REGION OF ACTIVE STREAM CAPTURE; THE NEW RIVER WATERSHED

The relatively rapid stream capture of the New River basin by the Roanoke River basin provides a unique example of topographic change within a tectonically inactive environment. A previous investigation of abandoned river deposits has shown the capture of ~225 km² of New River basin area, which has caused approximately 250 m of incision by the Roanoke River (Prince et al., 2011). Difference in base level elevations between the lower Roanoke to the higher New River could be the source of potential energy driving rapid incision (Prince et al., 2011). Significant incongruities in base level elevations at the boundaries of an aquifer can steepen the gradient and shift the groundwater divide further toward the higher elevation boundary (Yechieli et al., 2009). If a steep groundwater gradient and expanded groundwater basin exists beneath the Roanoke River tributaries, this would suggest a groundwater control on incision and capture. In this investigation we are currently recording average total head in ~20 private wells bi-monthly, and continuously logging water temperature in 7 springs. Average head elevations and constant-head river boundary conditions are incorporated into numerical models to calculate water levels and gradients throughout the entire region. Preliminary results show the groundwater divide is located within the New River surface watershed, with very slight change in regional gradients during a change in season. Initial logging of spring temperatures reveal spatial variations in temperature patterns along the surface divide, which could explain variations in surface capture extent and speed, assuming a groundwater influence. We will continue to record both head and temperature values through May, 2014. With additional information we hope to better understand the nature and influence of groundwater flow in this rapidly changing surface environment.