Column: Critical Technology Pilot Coming to Green Lake Watershed Will Filter Phosphorus | Editorial

A new “phosphorus sponge” pilot project in the Green Lake watershed will test the effectiveness of using the technology to rapidly intercept phosphorus before it has a chance to degrade the lake’s water quality.

Pictured is an example of the CAPture technology, the new small-scale filtration system, which will intercept phosphorus from a holding basin of an agricultural field in the Green Lake watershed.

With Green Lake’s water quality deteriorating, the Green Lake Management Planning Team is working within the 107 square mile watershed to install traditional management best practices. The accumulation of these practices helps reduce phosphorus, the biggest threat to Green Lake’s water quality.

However, the acceleration of climate pressures relative to the pace of implementation of best management practices may not lead to improvements quickly enough to avoid a potential ecological tipping point – a point where an ecosystem can no longer cope with environmental change and the ecosystem suddenly shifts to a less desirable state in which successful intervention is next to impossible.

In response, the Green Lake Association (GLA) is launching a pilot project this summer to test the feasibility of using field-scale technology to accelerate lake restoration.

“If we are serious about improving Green Lake’s water quality, we will not be successful if we rely solely on traditional lake management practices,” said GLA Executive Director Stephanie Prellwitz. “We are running out of time to depend solely on such a long-term approach, which is why innovation and technology must be part of the picture.”

The technology, called “CAPture Phosphorus Interception”, is a new filtration system that will be adapted to the outlet of an existing agricultural retention pond in the Green Lake watershed.

During large rain events, these runoff structures often fail to capture phosphorus pollution, which is exactly when most of the phosphorus load occurs.

This phosphorus sponge will intercept the phosphorus pollution generated by 96 acres before it has a chance to flow downstream to Green Lake. If the CAPTure system succeeds in removing phosphorus from agricultural runoff, GLA and its partners have identified another 50 retention basins where a similar approach can be applied.

This project will be conducted as a trial over the next three years by the GLA, in collaboration with the Green Lake County Land Conservation Department and consulting firm Kieser & Associates.

The project is funded through WDNR grants and donations from GLA members.

“This is a simple addition and modification to make our reservoirs more efficient for phosphorus capture,” said Todd Morris, a county environmentalist for the Green Lake County Department of Land Conservation (LCD).

The Green Lake LCD will modify the basin and install the system. The LCD plans to make the necessary changes to the basin by October and to install the system by the spring of next year’s thaw to maximize the amount of phosphorus captured.

With the recently completed lake quality study by GLA confirming that a 50% reduction in phosphorus load just to improve lake conditions to minimum standards and up to a 70% reduction to return Green Lake to the clean, oligotrophic lake , GLA and its partners are taking action with a range of phosphorus-reducing and lake-loving practices to help meet this challenge.

There is no question: Green Lake is an incredible lake that presents significant water quality challenges. By broadening their focus, GLA and its partners can better address the decline in lake water quality.

To learn more or follow the progress of this innovative technology in the Green Lake Watershed, sign up for the Green Lake Association emails at

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