SS4.12 Linking Science with Management of Freshwater Resources
Date: Thursday, June 13, 2002
Time: 4:00:00 PM
Location: Carson B
 
LathropRC, Wisconsin Dept. Natural Resources, Madison, WI, USA, rlathrop@facstaff.wisc.edu
Armstrong, D, E, Univ. Wisconsin-Madison, Madison, WI, USA, 
Marshall, D, W, Wis. Dep. Natural Resources, Madison, WI, USA, 
Panuska, J, C, Wis. Dep. Natural Resources, Madison, USA, 
 
POTENTIAL FOR HYPOLIMNETIC WITHDRAWAL TO REDUCE SEDIMENT PHOSPHORUS CONCENTRATIONS AND RELEASE RATES IN DEVIL'S LAKE, WISCONSIN
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Devil's Lake (Ao=151 ha, Zmax=15 m) has experienced increased algal growth (planktonic, filamentous and periphytic) leading to multiple water quality and lake use problems. While P inputs to this inherently infertile seepage lake are no longer high, P recycling from the lake's profundal sediments maintains high lake fertility. To reduce sediment P concentrations and release rates, hypolimnetic withdrawal will be conducted from September through mid-October for ~15 years beginning in 2002. This restoration method was supported by field and laboratory studies: (1) cores taken throughout the lake's profundal zone indicated that Fe-bound P concentrations were high in the top few centimeters, with overall concentrations highest in the deepest lake region, (2) between mid-June before hypolimnetic anoxia and late September after prolonged anoxia, the Fe-bound P mass in the top 2 cm of sediment declined by 40-42% indicating a significant P release to the overlying water each season, and (3) sediment P release rates declined by 57% after 10 "withdrawals" in a sediment core incubation experiment. These results and others as well as the overall lake restoration project will be presented.