Climate change impacts efforts to reduce phosphorus in Yahara watershed

County supervisors and water quality partnerships discussed strategies to reduce phosphorus in the Yahara watershed at a Dane County joint meeting Wednesday. 

CLA Deputy Director Paul Dearlove explained that the Yahara CLEAN Compact, a partnership formed in 2008 to reduce phosphorus in the lakes, has made progress in keeping phosphorus on the land, especially in rural areas. The partnership works with community members such as farmers, neighborhood associations and other groups to meet the phosphorus reduction goals.

“The more we can get the community engaged, learning [and] taking action on behalf of the lakes, the more we’re going to be able to reduce phosphorus, which, as we know, is the main driver of water quality concerns in the lakes,” Dearlove explained. 

Members of the Environment, Agriculture and Natural Resources Committee, Land Conservation Committee and the Lakes and Watershed Commission heard presentations from the Yahara Watershed Improvement Network, the Clean Lakes Alliance (CLA) and the Land and Water Resources Department. 

Phosphorus entering the Yahara watershed, which encompasses a large part of southern Wisconsin, including Madison, has been a major factor in producing blue-green algae that covers large parts of Madison’s lakes, according to the CLA. The algal blooms on Lake Mendota have negatively impacted groups like the University’s rowing teams. Along with E. coli, the blooms have caused increased beach closures.

Despite making progress, the CLA emphasized that there are considerable obstacles to lowering the amount of phosphorus in the watershed. Dearlove said that increased runoff caused by storms during this past year impacted the amount of phosphorus entering local bodies of water.

“It’s quite remarkable how much these increased storm loads and runoff conditions are influencing the loads that are getting into the lakes,” Dearlove said. 

In 2019, the fifth wettest year on record for southern Wisconsin, phosphorus entered Lake Mendota in record amounts, according to the CLA’s most recent state of the lakes report. 

The Wisconsin Initiative on Climate Change Impacts report found that extreme precipitation events — like those that affected south central Wisconsin in 2018 — are becoming more common in the state.

“We’ve been putting quite a bit of funds and efforts into reducing phosphorus in our lakes and it looks like we might just be slowing the increase of phosphorus in our lakes. But it doesn't really look like we’re taking a dent out of it,” District 6 Supervisor Yogesh Chawla said. “What can we do? Is it a question of just climate change, all those factors overwhelming our system so we’re not able to get to our phosphorus targets?”

Dearlove said that going forward, the alliance will try to “figure out ways of identifying strategies that not only control phosphorus but also capture, contain [and] infiltrate runoff.” 

Chawla said that his committees are already taking steps to “keep rain where it falls” through methods such as storing manure and acquiring land to convert into wetlands. 

“I put $4 million in the budget… to purchase land that has good potential for drainage and that can be converted to wetlands so the rain stays where it falls instead of running off directly into the rivers and streams and eventually into the Yahara River,” Chawla said after the meeting.  

The committees and commission also heard updates from the Yahara Watershed Improvement Network (Yahara WINS), a collaboration led by the Madison Metropolitan Sewerage District to reduce phosphorus. 

Director of Ecosystem Services Martye Griffin showed that instream phosphorus concentrations have stabilized at lower levels at monitoring locations. 

“Even with climate change, even with these big pulses of phosphorus that we do get, over the course of time we do see reductions and we actually do see it reflected in the water quality data,” Griffin explained. “The goal is to keep these lines continually trending down over the 20 year project.” 

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