2000-06-08_AgendaPacket - Laserfiche WebLink

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When developing an aquatic plant management plan for a shallow lake, it is critical to assure that the community who uses and values the lake understands the workings of their lake and the options and opportunities available for managing the lake. This is most effectively done in the context of a comprehensive lake management plan (see Osgood 2000). Snail lake Snail lake is a small (I 50 acres) shallow lake in the Twin Cities metro area of Minnesota. The lake has a littoral area comprising 87% of the total area and is one of the few lakes in the area not yet infested with Eurasian watermilfoil. Snail Lake is popular with lakeshore residents as well as anglers and recreational users through a county park on the lake's southern shore. The Snail lake Association had a number of concerns: • Excessive and increasing aquatic plant growth • Water level fluctuations and maintenance • The threat of Eurasian watermilfoil • Increasing recreational use conflicts A Situation Analysis found I) increasing and abundant aquatic plants was likely to be a result of varying lake levels, thus was cyclical rather than an increasing trend, 2) phosphorus concentrations were low and external inputs were also low, 3) the abundance of algae and the incidence of algae blooms was low, and d) the water was very clear. Snail lake is aplant-dominated shallow lake. The algae content in Snail Lake, as measured by seasonal average chlorophyll concentration, was 4.5 parts per billion (I 4-year average), which puts Snail Lake m the upper I O`" percentile of lowest algae content for all metro lakes. Similarly, the lake's water clarity averaged 12 feet, also putting it m the upper 10`" percentile of highest water clarity. The abundance of algae is 3.5 times lower and the clarity is I .4 times greater than other metro lakes with the same phosphorus content as Snail Lake. The users of Snail Lake enjoy the shallow lake bonus. The challenge for the Snail lake Assocation was to reconale the plant-dominated condition with the concerns they raised. The Association was presented with two alternatives for approaching the management of their lake: I . Working with the shallow lake and maintaining the status quo. This involves preventing a `switch to an algae-dominated condition. This also meant that open-water recreation would need to be controlled. A more traditional approach involving managing nutrients and controlling aquatic plants. Because many of the Association members wanted to provide more open water for active recreation, like water skiing, this is the approach they initially preferred. Following a thorough Situation Analysis, the Association was presented with these pros and cons for each approach: Working with the shallow lake e Pros