Monitoring equipment was installed in the fall of 1990, and sampling began in January of 1991. The USLE was developed by the U.S. Department of Agriculture to evaluate the sediment input from watersheds. The lake was sampled twice monthly from April through September and monthly from October to March. Samples were collected by a local resident and sent to the South Dakota State Health Laboratory in Pierre for analysis. The data necessary for input in the USLE was gathered by a local resident and personnel from the SD DENR.The major problems facing Swan Lake are predicated by its shallow depth.
Shallow depths can cause high turbidity, and the cloudy or dirty appearance of the water.
Turbidity can be caused by algae, tributary input, or resuspension of sediments by wind, boat motors, or bottom feeding fish. Concentrations of dissolved solids in Swan Lake were high enough to classify the lake water as moderately brackish. The high dissolved solids concentration is probably caused by the recharge of groundwater to the lake from springs in the Turkey Ridge Creek watershed. A high concentration of dissolved minerals enters the lake and the concentration further increases due to evaporation. In-lake sampling also showed Swan Lake to be hypereutrophic.