HR: 10:50h
AN: H52B-03    [Abstracts]
TI: Effects of Gravel Bars on Nutrient Spiraling in Bedrock-Alluvium Streams
AU: * Iobst, B R
EM: ben.iobst@vanderbilt.edu
AF: Dept. of Earth and Environmental Sciences, Vanderbilt University, VU Station B #351805, 2301 Vanderbilt Place, Nashville, TN 37235, United States
AU: Carroll, E P
EM: emilie.p.carroll@vanderbilt.edu
AF: Dept. of Earth and Environmental Sciences, Vanderbilt University, VU Station B #351805, 2301 Vanderbilt Place, Nashville, TN 37235, United States
AU: Furbish, D J
EM: david.j.furbish@vanderbilt.edu
AF: Dept. of Earth and Environmental Sciences, Vanderbilt University, VU Station B #351805, 2301 Vanderbilt Place, Nashville, TN 37235, United States
AB: The importance of the connection between nutrient transport and local stream geomorphology is becoming increasingly important. Studies have shown that the interconnectivity of nutrient cycles in the downstream direction is in part controlled by the distribution and size of gravel bars in low order streams, as hyporheic flow occurs dominantly through alternate and mid-channel gravel bars. For this investigation multiple gravel bars in a 3rd order bedrock-alluvium stream were studied to determine general relationships between nutrient spiraling and hyporheic flow. The first goal was to understand (1) the extent to which water moves through hyporheic zones and (2) the basic chemistry of the hyporheic water. The second part of the study was to understand how nutrients, notably nitrogen, are affected in their cycling by the relatively long residence times encountered in gravel bars during hyporheic flow. Wells were installed along a 600 m reach of Panther Creek, KY in selected bars, as well as in a secondary location involving a grid installation pattern in one large bar. Results have shown that hyporheic flow through gravel bars is an important factor in influencing stream chemistry. Background water chemistry surveys have shown that certain parameters, specifically ammonium and nitrogen concentrations vary downstream, and that the dominant control over these changes is gravel bar location. Rhodamine WT was used in field tracer tests to track the travel times of water through bars as well as partitioning of water between the open channel and hyporheic flows. Further tests will be conducted utilizing a stable isotope study to determine how nitrogen is affected by hyporheic flow, and what implications this has for nutrient transport. We expect results to show that the spacing and size of gravel bars is a dominant control in key nutrient spiraling parameters, namely uptake lengths and overall nitrogen cycling rates. This has implications for how natural systems will respond to human impacts, both through the modification of the physical template of stream systems as well as increased anthropogenic loading of nitrogen.
DE: 1813 Eco-hydrology
DE: 1825 Geomorphology: fluvial (1625)
DE: 1834 Human impacts
DE: 1871 Surface water quality
SC: Hydrology [H]
MN: 2007 Joint Assembly