HR: 09:00h
AN: NB21D-03 INVITED [Abstracts]
TI: Effects of Water Residence Time on Nitrate Removal in Flow-Regulated Backwater Lakes of the UMR Flood Plain
AU: * James, W
EM: jamesw1@svtel.net
AF: USACE Engineer Research and Development Center, Eau Galle Aquatic Ecology Laboratory, Spring Valley, WI 54767 United States
AU: Richardson, W
EM: william_richardson@usgs.gov
AF: US Geological Survey, Upper Midwest Environmental Sciences Center, LaCrosse, WI 54603 United States
AU: Strauss, E
EM: eric_strauss@usgs.gov
AF: US Geological Survey, Upper Midwest Environmental Sciences Center, LaCrosse, WI 54603 United States
AU: Soballe, D
EM: david.m.soballe@erdc.usace.army.mil
AF: USACE Engineer Research and Development Center, Eau Galle Aquatic Ecology Laboratory, Spring Valley, WI 54767 United States
AU: Barko, J
EM: john.w.barko@erdc.usace.army.mil
AF: USACE Engineer Research and Development Center, Eau Galle Aquatic Ecology Laboratory, Spring Valley, WI 54767 United States
AB:
We examined in 2004 nitrate retention in five backwater lakes that are connected to the UMR via flow-controlled culverts.
Nitrate loading and water residence time varied inversely as a function of culvert flow. Unlike engineered wetlands, we could not maximize source water nitrate concentration to increase loading. Under these constraints, maximum nitrate mass removal
(42 percent) coincided with a water residence time of about 2 days. Removal decreased as flow and lake flushing rate
increased. Hypothetical adjustments in flow and water residence time resulted in a 22 percent estimated load reduction.
However, estimated removal could improve by 50 percent, due to increased contact time. Our results indicate that water
residence time needs to be considered in connectivity design issues in order to maximize nitrate removal in backwater
systems. This design goal is more difficult to achieve for natural backwater systems given the more complex
interrelationships between flow, load, morphology, and water residence time.
DE: 0400 Biogeosciences
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly