Monday, June 4, 2007 - 4:45 PM
48

Propagation and dissipation of watershed signals along the river continuum: geomorphic, hydrologic and biogeochemical recovery trajectories of an urban stream

Emily S. Bernhardt1, Brooke A. Hassett1, Elizabeth B. Sudduth2, and Peter A. Cada3. (1) Department of Biology, Duke University, Durham, NC 27708, (2) University Program in Ecology, Duke University, Durham, NC 27708, (3) Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC 27708

As the final portion of the flowpath, stream ecosystems can exert disproportionate control on the timing, magnitude and form of watershed element outputs.  The capacity of stream ecosystems to alter watershed signals depends in large part on the relationships between the channel and its associated hyporheic and riparian zones.  Urbanization of watersheds tends to disrupt these connections, leading to dramatically simplified channel forms and reduced hyporheic and floodplain exchange.  A central question is over what spatial scale this watershed degradation is propagated along the stream continuum and, correspondingly, at what scale must restoration or preservation be done to mask or eliminate these biogeochemical signals.  In this talk we present new data documenting how hydrologic and biogeochemical outputs from an urban upper subcatchment are muted and transformed during transport through a protected lower watershed and geomorphically complex stream channel. 

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