Changes in sediment characteristics following drawdown of Big Muskego Lake, Wisconsin
James, William F.; Barko, John W.; Eakin, Harry L.; Helsel, Daniel R.
published: May 23, 2001
ArtNo. ESP141015103013, Price: 29.00 €
Changes in surficial sediment physical and chemical composItIOn and internal P loadings due to lake drawdown and refill to promote macrophyte growth in shallow Big Muskego Lake, Wisconsin were examined. Thirteen percent of the sediment area was exposed for ⁓ 1 year, while over 80 % of the sediment area was exposed for a period of 6 months. Mean sediment (upper 10 cm) moisture content and organic matter content decreased (92 % to 86 % and 45 % to 39 %, respectively), while sediment density increased from a mean of 0.078 g/mL to 0.149 g/mL due to lake drawdown, suggesting consolidation of sediment and some oxidation of organic matter in the sediment. Porewater ammonium-nitrogen and soluble reactive phosphorus, and laboratory-based rates of phosphorus release from sediment, increased substantially shortly after lake refill, but then declined 1 year later. Total phosphorus and extractable phosphorus forms of the surficial sediment declined in both concentration and mass after drawdown, which may be attributed to uptake by biota. These positive (i.e., sediment consolidation) and negative (i.e., sediment nutrient release) impacts of drawdown on sediment dynamics need to be considered in shallow lake rehabilitation programs.