Column: Critical technology pilot project coming to the Green Lake watershed will filter phosphorus | Editorial

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

CAPTure box from Keiser

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

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

Yet, the acceleration of climate pressures compared to the pace of best management practice implementation may not result in improvements fast enough to avoid a potential ecological tipping point — a point when an ecosystem can no longer cope with environmental change, and the ecosystem suddenly shifts to a less desirable state where successful intervention is nearly 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 the lake’s restoration.

“If we are serious about improving Green Lake’s water quality, we will not be successful if we solely rely on traditional lake management practices,” GLA Executive Director Stephanie Prellwitz said. “We are short on time to exclusively depend 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 novel filtration system that will be retrofit to the outlet of an existing agricultural retention pond in the Green Lake watershed.

During big rain events, these runoff structures often fail to capture phosphorus pollution, which is exactly when most phosphorus loading occurs.

This one phosphorus sponge will intercept phosphorus pollution generated from 96 acres before it has a chance to flow downstream to Green Lake. If the CAPTure system is successful in removing phosphorus from agricultural runoff, the GLA and its partners have identified 50 other retention ponds where a similar approach may be applied.

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

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

“It’s an easy add-on and modification to make our basins more efficient for capturing phosphorus,” said Todd Morris, county conservationist for the Green Lake County Land Conservation Department (LCD).

The Green Lake LCD will modify the basin and install the system. The LCD plans to make necessary modifications to the basin by October and have the system installed by spring thaw next year, to maximize the amount of phosphorus captured.

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

There is no doubt: Green Lake is an incredible lake that has significant water quality challenges. By broadening their focus, the GLA and its partners can better tackle the lake’s declining water quality.

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

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