It's been more than a decade since Wisconsin cracked down on phosphorus. Has it helped protect our lakes and rivers?

Laura Schulte Madeline Heim Caitlin Looby
Milwaukee Journal Sentinel

In 2010, Wisconsin enacted new rules to limit the amount of phosphorus flowing into its waterways.

It was, and remains, one of the most stringent set of regulations in the country to address the pollutant, which was filling the state's beloved waters with foul-smelling algae blooms.

After more than a decade, progress has been made. Between 2010 and 2020, rivers around the state started to show reductions in phosphorus. Farmers started comparing notes about how to reduce runoff from their fields, use of phosphorus fertilizers decreased and industries cut down on discharge.

But experts say that progress isn't happening fast enough, or at least can't measure up to the magnitude of the problem. The number of water bodies in Wisconsin impaired by phosphorus has increased, for example, from 721 in 2016 to 1,102 in 2022.

Still, these experts see a path forward for continuing to improve water quality.

"It's clear that these (phosphorus) rules alone will not, in many cases, allow us to achieve our water quality goals," said Scott Laeser, water program director for Clean Wisconsin. "But they are a really important step along the way to doing so."

Beachgoers swim near a blue-green algae bloom near Cornucopia Beach on Lake Superior. Blue-green algae blooms typically happen in the parts of the lake where people recreate, like the shorelines and inland waterways.

What is phosphorus?

Phosphorus is an important building block of cells and helps plants grow.

It's a key ingredient in fertilizers spread on cropland, including manure, which is a natural fertilizer.

Phosphorus gets into waterways in a variety of different ways, according to the Department of Natural Resources, including from point sources, such as municipal and industrial wastewater treatment plants; nonpoint sources, such as runoff after heavy snow or rain that carries fertilizer, manure or even soil with it; and natural sources, such as erosion and the build-up of sediment in lakes.

More than 80% of phosphorus in Wisconsin waters originates from nonpoint sources.

Why is it bad for the environment?

While phosphorus is important for plant life, it can cause explosive growth of aquatic plants and algae when too much of it seeps into a body of water. That plant and algae growth sucks up dissolved oxygen, making it difficult for fish and other aquatic life to survive.

Large algae blooms are unsightly, but some of them are also dangerous — killing fish and pets and sickening humans that come into contact with their toxins. During the summertime, people may come across a public beach that is closed because of an algae bloom.

More:Here's what you should know about blue-green algae

Phosphorus runoff from much of Wisconsin flows down the Mississippi River and into the Gulf of Mexico, where it contributes to the dead zone, a more than 3,000 square-mile area where low oxygen chokes off aquatic life. A similar phenomenon is happening in the bay of Green Bay, where blue-green algae blooms can be seen from space.

Why did Wisconsin enact stricter rules than other states?

At the time the phosphorus rules were proposed, many surface water bodies were having issues with harmful algae blooms and eutrophication, which occurs when the environment becomes enriched with nutrients, increasing the amount of plant and algae growth.

Regulators knew they needed to take action to prevent conditions from growing any worse, and proposed some of the strictest phosphorus regulations in the United States.

Wisconsin is one of only a few states to even have phosphorus regulations, said Adrian Stocks, a DNR water quality program director. They were enacted to protect the waters that are such a key part of the state's identity.

"I think there was really just a recognition within the state that that the nutrient loading and the eutrophication issues within the states water resources needed to be addressed," he said. "And there was the political will at that time to enact these numeric criteria in order to provide the benchmarks for facilities to meet, in order to reduce those sources of nutrients within the water bodies."

The state finds itself in a different political environment today, and other efforts to set water quality rules have been slower to progress — like PFAS, for which lawmakers allowed standards to go into effect last year after years of heated debate.

Laeser said it's "fair to observe" that the strict phosphorus rules contributed to efforts to undermine the state's rule-making process, especially in an increasingly partisan political climate.

The rules drew ire at the time from the state's business lobby, including Wisconsin Manufacturers & Commerce, which argued that because Wisconsin was at the forefront of such regulations, state companies would be paying higher costs for compliance than their competitors. At the same time, environmental groups had threatened to file a lawsuit if the regulations weren't set.

"It's clear that we have some hurdles — that have only grown — to use regulatory tools to address water quality," he said, but added that he's optimistic that stakeholders could come together to chart a different path forward.

More:'The Devil's Element' chronicles humanity's deadly dance with phosphorus

What have the rules accomplished?

While the issue of phosphorus in Wisconsin's surface water persists, things are getting better, Stocks said.

"It has taken us generations to get to this point, and it will take likely decades to get back out and see the improvements," he said. "But we have seen phosphorus trends within the surface waters decline since the implementation of the rule, so that is trending in the right direction."

The rules were also unique for the innovative methods they prompted for point and nonpoint sources to work together to reduce pollution: allowing a wastewater treatment plant to work with a farmer, for example, to reduce runoff on his land so that by the time it comes out of the pipe at the plant, it's already cleaner.

What are the regulations?

The criteria for the amount of phosphorus allowed in water varies by the type of water body being measured.

For Wisconsin, the amount of phosphorus allowed in waterbodies includes:

  • Rivers: 100 micrograms per liter
  • Streams: 75 micrograms/liter
  • Reservoirs: 30-40 micrograms/liter
  • Lakes: 15-40 micrograms/liter

The Great Lakes follow separate guidelines set forth by the Great Lakes Water Quality Agreement between the U.S. and Canada. The recommended phosphorus loads for Lake Michigan is 7 micrograms per liter and 5 micrograms per liter for Lake Superior.

How are the rules affecting algae blooms in the Great Lakes?

Cyanobacteria, or blue-green algae, on the surface of Green Bay just north of the Leo Frigo Memorial Bridge.

In Lake Michigan, phosphorus causes a lot of problems near shore.

Every summer, agricultural runoff from the Fox River feeds algae blooms in the bay of Green Bay. Large blooms can suck the oxygen out of the water, creating “dead zones” where aquatic life can’t survive. The dead zones also have a major economic impact.

Algae blooms have even recently been observed along the shores of Lake Superior, although it’s not yet clear why.

While most of Wisconsin’s water bodies are seeing progress, “the Fox River is going in the wrong direction,” said Melissa Scanlan, Director for the Center for Water Policy at the University of Wisconsin-Milwaukee. 

There is a lot of legacy phosphorus in the soil that’s leaking into the Fox River watershed, Scanlan said. This causes a lag effect where it takes a long time to see the benefits of any land use change.  

There are no silver bullets in dealing with phosphorus runoff in the Fox River, she said, but there need to be transformative changes that work for farmers.

What about the rest of Lake Michigan?

There’s a different kind of phosphorus problem out in the open lake.

Phosphorus is a necessary part of the lakes’ food web. Plants and phytoplankton that fish rely on need phosphorus to grow.  

But invasive mussels that now cover the bottom of Lake Michigan have created a phosphorus “desert” in the deeper waters offshore. These mussels filter nutrients, sucking out phosphorus from the water and making there less to go around. 

The lack of phosphorus is part of the reason why invasive mussels have made the lake water clearer. But when they die off they release that phosphorus back into the lake, creating a phosphorus pulse. 

In fact, invasive quagga mussels are now in control of the phosphorus cycle in all of the lakes, except Lake Superior.

What challenges still exist?

Even as farmers and others adapt their practices to reduce runoff, the state also has to grapple with legacy phosphorus — that is, phosphorus that has built up over time from fertilizer and other sources and is seeping into waterways. A 2017 study of a creek in Dane County found that phosphorus at the core of some stream bottoms was 120 years old.

Phosphorus runoff also increases after extreme precipitation events, which are projected to be more frequent as the climate changes. A 2017 study from the University of Wisconsin-Madison's Center for Limnology found that phosphorus "pulses" into waterways after extreme rainfall, building on previous research that showed waterways receive most of their phosphorus in just a dozen or two events per year. The bigger the rainstorm, the more phosphorus was flushed downstream, the UW study found.

Another issue is the different regulations applied to point and nonpoint sources — and the resources they have to address the problem.

Point sources, like a wastewater treatment facility, for example, can measure the phosphorus coming out of the pipe connecting their building to a nearby waterway. And if they need to make upgrades that help them reduce phosphorus levels, they can pass those costs on to ratepayers.

Farm fields, on the other hand, a nonpoint source, don't have one specific place to measure how much phosphorus is coming off a given field. And farmers can't charge more for their harvest if they need to spend money on reducing their phosphorus levels.

The current rule requires that all farms have a plan to manage their nutrients that includes having levels of phosphorus below a 6 on the Wisconsin Phosphorus Index, a tool created to manage that runoff.

But the rule also says that the state would have to pay 70% of the costs of any on-farm projects to reduce phosphorus in order to enforce that requirement, said Sara Walling, who worked for the state Department of Agriculture, Trade and Consumer Protection when the rule was being written.

Agricultural reductions lag, then, because the state can't require anything, while for point sources, "day one came and all the wastewater dischargers were on notice immediately," said Walling, who now serves as senior policy manager for agriculture and restoration for the Alliance for the Great Lakes.

What's more, data collected since the rule was enacted has led scientists to realize that a phosphorus index reading of 6 included in a farm's nutrient management plan actually isn't enough to meet the water quality standards they wanted for lakes and streams. About six pounds of phosphorus are lost annually from an acre of cropland with an index reading of 6, Walling said.

Laura Schulte, Madeline Heim and Caitlin Looby cover environmental issues for the Milwaukee Journal Sentinel.