HR: 11:00h
AN: NB52E-03    [Abstracts]
TI: Hydrogeomorphic Controls on Spatiotemporal Sediment and Nutrient Dynamics Following a Low-head Dam Removal
AU: * Ahearn, D S
EM: dsahearn@ucdavis.edu
AF: Department of Land, Air, and Water Resources, University of California, Davis, CA 95616 United States
AU: Dahlgren, R A
EM: radahlgren@ucdavis.edu
AF: Department of Land, Air, and Water Resources, University of California, Davis, CA 95616 United States
AB: In this study we address sediment and nutrient export following removal of a 3 m dam on Murphy Creek, California and examine the restored reach in an effort to understand the hydrobiogeochemical mechanisms driving nutrient dynamics in the recovering system. Following removal, sediment and nutrient yields increased by an order of magnitude over the previous two years. Geomorphic surveying indicated that the majority of sediment transport occurred in pools and in the lowest 50 m of the restored reach. Phosphate export occurred primarily during large storms with the reach acting as a phosphate sink during most flow conditions. The majority of N was sourced to areas within the sediment wedge that had high extractable N concentrations (NH₄⁺ and NO₃^{-) and dried out on a seasonal basis. Near the restored dam site year-round water saturation inhibited nitrification and the export of N as NO₃-, instead, this wetland area acted as an NH₄+ sink and leached little NO₃- to the channel. Nitrogen leaching from sediments occurred after removal, in autumn 2003, and again during the following autumn, indicating that N leaching from sediments is largely a seasonal process which may affect downstream aquatic ecosystems for years to come.}
DE: 1824 Geomorphology (1625)
DE: 1857 Reservoirs (surface)
DE: 1871 Surface water quality
DE: 1890 Wetlands
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly