HR: 14:30h
AN: H13D-05 INVITED     [Abstracts]
TI: Are Big Basins Just the Sum of Small Catchments?
AU: * Shaman, J
EM: jshaman@fas.harvard.edu
AF: Harvard University, Dept. Earth and Planetary Sciences 20 Oxford St., Cambridge, MA 02138 United States
AU: Stieglitz, M
EM: marc.stieglitz@ce.gatech.edu
AF: Georgia Institute of Technology, School of Earth and Atmospheric Sciences, Dept of Civil and Environmental Engineering, 206 Daniel Lab, Atlanta, GA 30332 United States
AU: Burns, D
EM: daburns@usgs.gov
AF: United States Geological Survey, 425 Jordan Road, Troy, NY 12180 United States
AB: ² Many challenges remain in extending our understanding of how hydrologic processes within small catchments scale to larger river basins. We examine how low-flow runoff varies as a function of basin scale at 11 catchments, many of which are nested, in the 176km² Neversink River watershed in the Catskill Mountains of New York. Topography, vegetation, soil and bedrock structure are similar across this river basin, and previous research has demonstrated the importance of deep groundwater springs for maintaining low-flow stream discharge at small scales in the basin. Therefore, we hypothesized that deep groundwater would contribute an increasing amount to low-flow discharge as basin scale increased, resulting in increased runoff. Instead, we find that, above a critical basin size of 8 to 21km², low-flow runoff is similar within the Neversink watershed. These findings are broadly consistent with those of a previous study that examined stream chemistry as a function of basin scale for this watershed. However, we find physical evidence of self-similarity among basins greater than 8km², whereas the previous study found gradual changes in stream chemistry among basins greater than 3km². We believe that a better understanding of self-similarity and the subsurface flow processes that affect streamrunoff will be attained through simultaneous consideration of both chemical and physical evidence. We also suggest that similar analyses of stream runoff in other basins that represent a range of spatial scales, geomorphologies and climate conditions will further elucidate the issue of scaling of hydrologic processes.
DE: 1824 Geomorphology (1625)
DE: 1829 Groundwater hydrology
DE: 1836 Hydrologic budget (1655)
SC: Hydrology [H]
MN: 2005 Joint Assembly