Restoration of a Wisconsin (USA) seepage lake by hypolimnetic withdrawal

摘要

Devil's Lake (Table 1, Fig. 1) is the centerpiece to Wisconsin's most popular state park (Lillie & Mason 1986, Lathrop et al. 2004). The dimictic seepage lake is renowned for its clear waters (compared to other lakes in southern Wisconsin) due to low levels of phosphorus (P) entering the lake from its small, mostly forested watershed. However, cultural inputs of P were excessive at times for over a century until those sources ended in the early 1980s. Unfortunately, the pollution legacy remains in Devil's Lake because it has no outlet for dilutional flushing. While external P loadings are now low, internal P loading rates are high, causing multiple water quality problems. To reduce these internal loading rates and to return the lake to its earlier pristine state, a hypolimnetic withdrawal siphon system was installed in 2002. In this paper we summarize information about the lake and its water quality problems, describe the withdrawal system, and present data for the first two years of withdrawals (2002-2003).