HR: 1330h
AN: H12B-0978    [PDF]
TI: Soils and Springs - Controls on the Isotope Hydrology of 3 Appalachian Landscapes
AU: * O'Driscoll, M A
EM: odriscoll@psu.edu
AF: Pennsylvania State University, School of Forest Resources, Land and Water Building, University Park, PA 16802 United States
AU: DeWalle, D R
EM: drdewalle@psu.edu
AF: Pennsylvania State University, School of Forest Resources, Land and Water Building, University Park, PA 16802 United States
AU: McGuire, K J
EM: Kevin.McGuire@orst.edu
AF: Oregon State University, Department of Forest Engineering, 4 Peavy Hall, Corvallis, OR 97331 United States
AU: Gburek, W J
EM: Bil.Gburek@ars.usda.gov
AF: U.S. Department of Agriculture-Agricultural Research Service, Pasture Lab Building, University Park, PA 16802 United States
AB: Environmental isotopes, such as O-18 and D, have been used to study hydrological processes in a variety of settings. The seasonal variations of stream baseflow isotopic composition at a catchment outlet are often used to estimate the residence time of groundwater within a catchment. Residence time models can be improved with information related to the spatial variability of baseflow isotopic composition within a catchment. This study aimed to quantify the annual variations in O-18 composition of waters within several Appalachian watersheds representative of 3 common landscape types in central Pennsylvania: the Valley and Ridge-shale (Mahantango Creek); Valley and Ridge-carbonate (Buffalo Run); and Appalachian Plateau-sandstone (Benner Run). Bi-weekly precipitation, snowmelt, soil water, and baseflow isotopic composition data were collected for the 3 catchments over one year (May 1999-May 2000). Preliminary results suggest that soils at these sites can effectively damp seasonal precipitation O-18 signals by the time they reach depths of 1.62-2.85 meters in the subsurface. This suggests that seasonal isotopic composition variations in baseflow are due to waters that drain the shallower soils within these catchments. The presence of springs was found to exert an influence on baseflow isotopic composition within each of the catchments. Two watersheds contained diffuse-fed springs, which resulted in a damping of seasonal variability of baseflow isotopic composition downstream. The remaining watershed contained a conduit spring, draining carbonate bedrock. This spring discharge resulted in an increase in seasonal variability of baseflow isotopic composition downstream. The seasonal variability of baseflow isotopic composition observed at the catchment outlets was a result of the combination of several distinct water sources: slow-draining groundwater; fast-draining near-channel groundwater; and spring discharges. An improvement in modeling of residence times of these catchments may be achieved by quantifying the contributions of spring discharges.
DE: 1860 Runoff and streamflow
SC: Hydrology [H]
MN: 2003 Fall Meeting