Journal of Student Research 2018

74 Journal Student Research Before implementation of management, the lake exhibited summer means of 0.11 mg/L P, 82 μg/L chlorophyll, and 1.1 m Secchi transparency (James et al. 2002). Consequently, Half Moon Lake was included on Wisconsin’s impaired waters list in 1998 (Half Moon Lake Implementation Taskforce 2010). The P budget was dominated by sediment internal P loading, curly leaf pondweed (CLP) decomposition, and sediment resuspension from motor boat activity, while storm water runoff contributed only ~ 5% of the P load to the lake (James et al. 2002). Sediment internal P loading was controlled by an aluminum sulfate (alum) treatment in 2011 and 2017 (James 2017), motor boat activity was banned in 2007, and CLP has been controlled by annual endothall herbicide treatments since 2009. However, since the lake is still impaired, there is concern that urban runoff and P loading will become an important source and subsidize algal productivity after management of these internal P loading sources. Management has been implemented to curb urban watershed P loads. BMPs such as constructing driveways and parking lots to slope in a particular manner that encourages runoff to flow onto grassy and rock-based infiltration areas; constructing rain gardens and rock islands to collect and filter runoff; creating grassy buffers around impervious areas (Fig. 2) street sweeping to remove some of the pollutants on the street; and in-lake treatment with alum have been used to manage phosphorus inputs (Half Moon Lake Implementation Taskforce 2010).

Figure 2. Photographs of various rock islands and grass buffers added to parking lots during the Luther Hospital campus expansion.