In the summer of 2018, residents throughout Wisconsin awoke to the news that blue-green algae blooms rendered their lakes temporarily toxic. Green Lake was not part of this infamous list, but the same culprit fuels its weed and algae growth: phosphorus, a naturally occurring element found in eroding soil, excess fertilizer, and a host of other urban and rural sources.
Various human impacts concentrate phosphorus loading to nearby waterways, accelerating natural lake aging from centuries to years. This process of lake degradation stimulates indicators that range from moderate, like excessive weed and algae growth seen on Big Green Lake to severe, like blue-green algae blooms seen this summer on Little Green, Monona, and Winnebago Lakes.
Although Big Green remains safe and swimmable, the lake’s long-term trends of high phosphorus levels and a low-oxygen dead zone indicate that its water quality is not what it once was. It’s critical to get ahead of moderate lake degradation before Green Lake reaches an ecological tipping point, when water quality success becomes much harder.
Green Lake Association (GLA) is a not-for-profit organization that commits all of its resources to improving Big Green Lake’s water quality. The Wisconsin Department of Natural Resources listed Big Green Lake as an impaired water body in 2014 because it does not meet optimal conditions.
GLA and other members of the lake management planning (LMP) team have developed a long-term rehabilitation plan to improve the lake’s water quality. The goal is to implement a suite of conservation efforts that outpace Green Lake’s decline. The GLA is advancing three pillar projects in support of the team’s rehabilitation plan aimed at collaborating with local farmers, restoring degraded streams and battling the harmful pollutants in them, and defending Big Green’s waters against invasive species.
These initiatives include, among others, restoring 5,700 feet of degraded streambank on Dakin Creek and restocking the creek with brook trout, an indicator of clean water; installing a network of demonstration farms; continuing the aggressive removal of invasive carp; and installing two decontamination stations at public boat launches to prevent additional invasive species from infecting the lake.
Green Lake did not have beach-closing blue-green algae blooms like many other lakes this year, though the lake’s large volume and depth can mask its water-quality challenges. For GLA and members of the LMP team, the most effective way to ensure a clean and safe lake for current and future generations is to be proactive now.
Stephanie Prellwitz is the executive director at Green Lake Association.