Rehabilitation of a Shallow Lake

PURPOSE: This technical note examines changes in sediment physical and chemical charac-teristics as a result of drawdown and refill of shallow Big Muskego Lake (Wisconsin) to promote macrophyte growth. Information obtained from this study may be used to assess positive (i.e., sediment consolidation) and negative (i.e., sediment nutrient release) impacts of drawdown on sediment dynamics and the potential for macrophyte growth in shallow lake rehabilitation programs. BACKGROUND: The positive roles played by submersed aquatic macrophytes in reducing sediment resuspension in shallow lakes and reservoirs may often be disturbed by high external nutrient loadings and turbidity, unexpected lake level fluctuations, explosions of benthic fish communities, and/or other ecosystem-level stresses such as strong storms or high winds, resulting in macrophyte community instability and a changeover to a more turbid, algal-dominated state with loss of macrophyte dominance (Scheffer 1990; Scheffer et al. 1993). One of the goals of shallow lake rehabilitation, therefore, is the reestablishment and maintenance of stable submersed macro-phyte communities for purposes of reducing sediment resuspension, sediment export, and improving water quality (Scheffer et al. 1994). Scheffer (1998) describes several restoration techniques for improving the shallow aquatic environment for macrophyte growth. After favorable water qualit