HR: 17:48h
AN: H44B-10    [Abstracts]
TI: Hydro-Ecological Linkages in Urbanizing Watersheds: The Role of Small Streams in Controlling Nitrogen Export
AU: * Claessens, L
EM: claessen@rohan.sdsu.edu
AF: Department of Geography, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182-4493 United States
AU: * Claessens, L
EM: claessen@rohan.sdsu.edu
AF: Department of Geography, University of California Santa Barbara, Ellison Hall 3611, Santa Barbara, CA 93106-4060 United States
AU: Tague, C
EM: ctague@mail.sdsu.edu
AF: Department of Geography, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182-4493 United States
AU: Band, L E
EM: lband@email.unc.edu
AF: Department of Geography, University of North Carolina, 200 S. Elliot Road, Chapel Hill, NC 27599-3220 United States
AU: Groffman, P M
EM: groffmanp@ecostudies.org
AF: Institute of Ecosystem Studies, Box AB, Millbrook, NY 12545 United States
AU: Kenworthy, S T
EM: stephen.kenworthy@wku.edu
AF: Department of Geography and Geology, Western Kentucky University, 1 Big Red Way, Bowling Green, KY 42101-3576 United States
AB: The terrestrial-aquatic interface plays an important role in watershed nitrogen cycling. We assess the relative role of terrestrial and in-stream processes in the retention, transformation and mobilization of nitrogen, by combining hydro-ecological modeling with field measurements, geographic information systems and remote sensing, to address relevant processes and related patterns across a range of spatial and temporal scales. The Regional Hydro-Ecological Simulation System (RHESSys), a terrestrial hydro-ecological watershed model, is coupled within a geographic information system to a flow and water quality model for streams. Model development and application focuses on Baisman Run, a small, urbanizing watershed, located within the Baltimore Ecosystem Study Long Term Ecological Research program. Here we mainly report on results from our field data collection component. Field measurements include nutrient monitoring, solute additions and nitrate stable isotopes. To estimate nutrient uptake rates from solute additions, we adapted a transient storage model (OTIS) to account for nutrient saturation during the addition. Over time (i.e., several years), we observe a strong relationship between nitrate loss and flow conditions; nitrate loss was detected only at low to medium flows, while dilution dominates higher flows. Over space, stream characteristics exercise a strong control on nitrogen uptake. Ammonium uptake is related to stream size and reflects spatial variation in water/sediment contact. Transient storage, although it effects hydraulic residence time, does not necessarily translate into higher rates of biogeochemical processing in these headwater streams. Overall, our measurements and preliminary modeling results suggest that in urbanizing watersheds, small streams play a spatially and temporally complex role in controlling watershed nitrogen export. Subsequent work will further high-level integration between process-based models, field data collection and other data sources, to highlight the importance of ecotone processing and assess the impact of land-use change on watershed nitrogen export.
DE: 1803 Anthropogenic effects
DE: 1871 Surface water quality
DE: 0400 Biogeosciences
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting