Lee Daly, who spearheads the Big Swan Lake Improvement District’s (LID) alum treatment project, took Secchi disk readings in both north and south basins to measure water clarity before, during and after applications. The results were notable. In the south basin where Lake Restoration, Inc. applied the alum, or aluminum sulfate, water clarity depth on Oct. 1 before treatments began was 5 feet. After applications started, clarity depth on Oct. 8 increased to 7 feet. On Oct. 16 after the Lake Restoration project wrapped up for the year, the Secchi reading showed water clarity increased to 13 feet. Water clarity also improved in the north basin, despite not being treated. Readings were 7 feet on Oct. 1, 7.5 feet on Oct. 8, and 10.5 feet on Oct. 16.
Long-term benefits follow as the alum binds algae-feeding phosphorus to the lake bottom, preventing it from re-entering the main body of water during lake turnover or other turbulence.