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  • January 23, 2023

    Analyzing the Impact of Wisconsin’s Phosphorus Rules on Water Quality

    Wisconsin passed some of the nation’s earliest and most comprehensive phosphorus regulations in 2010. Anya Janssen and Melissa Scanlan discuss Wisconsin’s phosphorus rules and offer an invitation to the statewide phosphorus conference on Feb. 7, 2023.

    Melissa K. Scanlan and Anya T. Janssen

    In 2010, Wisconsin passed some of the earliest and most comprehensive phosphorus regulations in the nation. Environmental Protection Agency (EPA) holds up Wisconsin as a model for Region 5 states (the upper Midwest).

    Wisconsin is one of just four states that has adopted total phosphorus and total nitrogen criteria for two or more waterbody types.1

    In February, a statewide conference brings together academics, water and agricultural professionals, agency representatives, farmers and producers, lawyers, and lawmakers to evaluate the impact of Wisconsin’s phosphorus rules on water quality.

    About Wisconsin’s Phosphorus Rules

    Wisconsin’s rules are notable because they address both point and nonpoint source pollution with management mechanisms designed to incentivize water quality improvement.

    Wisconsin’s phosphorus rules are contained in four main sections of Wisconsin law:​ Wis. Admin. Code chapters:​

    • NR 102 (Phosphorus);

    • NR 217 (Effluent standards and limitations for phosphorus);

    • NR 151 (Posphorus index performance standard); and

    • Wis. Stat. section 283 (Trading of water pollution standards).

    Section NR 102 establishes specific numeric criteria for total phosphorus in surface waters. The goal of this section is to protect freshwater resources for lawfully designated uses. Numeric criteria for total phosphorus concentrations vary depending on the type of waterbody. In Wisconsin, waterbody types are categorized by: (1) rivers, streams, and impounded flowing waters; (2) lakes and reservoirs; and (3) the Great Lakes.

    Section NR 217 sets effluent standards and phosphorus limitations on discharges to surface waters. This section is applicable to point sources that must obtain WPDES permits prior to discharging wastewater. Water quality based effluent limitations for phosphorus are established at the point of discharge and are calculated based on applicable numeric criteria for total phosphorus set in NR 102.

    Section NR 217 and Wis. Stat. section 283 establishes two market mechanisms to encourage reductions in phosphorus runoff to waterways: (1) adaptive management and (2) water quality trading. Both options allow point source producers to come into compliance with phosphorus limitations and criteria by partnering with other point and nonpoint sources to reduce total phosphorus in a watershed.

    Section NR 217 establishes the legal requirements for the adaptive management compliance option for point source facilities. Point source producers of phosphorus may come into compliance with NR 217’s phosphorus limits by financing phosphorus reduction projects for other point or nonpoint sources within the same watershed. The purpose of adaptive management is to meet applicable numeric phosphorus criteria to improve water quality.

    Wis. Stat. section 283​ authorizes the water quality trading compliance option available to WPDES permit holders. Point source producers of phosphorus may come into compliance with effluent limits by purchasing phosphorus reduction credits from another compliant party within the same watershed, thus offsetting their point source discharges. The purpose of water quality trading is to ensure compliance with permit discharge limits to reduce the overall phosphorus concentration.

    In addition to the two market mechanisms above, the EPA approved a statewide multi-discharger variance that extends the timeline for point source facilities to comply with low-level phosphorus limits. Multiple point sources may be covered under the multi-discharger variance if they commit to taking steps to reduce phosphorus within their watershed.

    Section NR 151 creates phosphorus index performance standards applicable to nonpoint source crop and livestock producers. Performance standards are set using the Wisconsin Phosphorus Index (P Index), a planning and assessment tool designed to estimate and manage phosphorus runoff to surface waters on a field-by-field basis.

    The P Index is maintained by UW-Madison's College of Agricultural and Life Sciences. P Index values estimate phosphorus runoff and are calculated using a variety of factors, including soil conditions, crop type, tillage practices, manure and fertilizer applications, and long-term weather patterns. The higher the P Index value is for a given field, the greater the likelihood that the field is contributing to phosphorus pollution in each surface waterbody.

    Finally, Section NR 119 went into effect in October 2022. This section allows any person to submit a request for WDNR review to adopt a site-specific criteria for a waterbody that is more or less stringent than statewide criteria. Site-specific evaluation of a waterbody's designated use depends on an ecosystem’s response indicators to phosphorus and the waterbody’s overall biotic integrity.

    Melissa Scanlan headshot Melissa Scanlan, is a professor and director of the Center for Water Policy at the UW-Milwaukee’s School of Freshwater Sciences.

    Anya Janssen headshot Anya Janssen, San Diego 2022, is a water policy specialist with the Center for Water Policy at UW-Milwaukee’s School of Freshwater Sciences.

    Register Now for the Phosphorus Conference on Feb. 7, 2023

    The objective for Phosphorus: Lessons from 10+ Years of Numeric Standards for Wisconsin’s Waters is to share a retrospective analysis on Wisconsin’s phosphorus rules, evaluating statewide implementation, farmer/producer compliance, and impact on the state’s water quality.

    Wisconsin’s phosphorus rules have been in effect for just over a decade. The conference will deliver a timely assessment of the state’s phosphorus regulatory impact over the last 10 years.

    Phosphorus pollution poses a significant threat to the health and stability of Wisconsin’s waters. Excess phosphorus runoff to surface waters produces an ecological imbalance that leads to nuisance or harmful algal blooms, fish kills, and human illness. Waterbodies impaired by phosphorus pollution threaten public health, reduce recreational use, and decrease property values.

    A diverse body of academic researchers, water and agricultural professionals, farmers, producers, and agency representatives from EPA Region 5, WDNR, and DATCP, will offer valuable multidisciplinary perspectives on Wisconsin’s phosphorus rules and the ongoing challenge of phosphorus-impaired water bodies. The goal of this conference is to discuss the effectiveness of Wisconsin’s phosphorus rules, identifying implementation gaps to inform a future research and policy agenda.

    The Conference Planning Committee, led by the Center for Water Policy at UW-Milwaukee’s School of Freshwater Sciences, brings together leaders from WDNR, DATCP, UW-Extension, UW-Madison, UW-Stout, UW-Stevens Point, and the Alliance for the Great Lakes. It is supported by the Freshwater Collaborative of Wisconsin.

    Panels and Presenters

    The keynote speaker is New York Times bestselling author Dan Egan. He is the Brico Fund Journalist in Residence at the Center for Water Policy at UW-Milwaukee’s School of Freshwater Sciences​. He is author of The Death and Life of the Great Lakes. He will provide insight from his forthcoming book, The Devil’s Element: Phosphorus and a World Out of Balance.

    Agency representatives from EPA Region 5 and WDNR will lay the regulatory groundwork for Wisconsin’s approach to managing point and nonpoint source phosphorus pollution on the conference’s first panel. DATCP will discuss voluntary compliance approaches for nonpoint sources. Panelists will highlight relevant sections of the federal Clean Water Act and explain the cooperative relationship between the EPA and WDNR. Attendees will gain an understanding of Wisconsin’s various regulatory and voluntary mechanisms for phosphorus management.

    A morning academic panel will explore the relationship between land use management, phosphorus runoff, and water quality. Panelists will present findings related to issues of legacy phosphorus, the effectiveness of local ordinances on water quality outcomes, nutrient-induced dead zones, and alternative land use plans for managing and reducing phosphorus.

    An afternoon academic panel will focus on Wisconsin’s phosphorus policy implementation and the various market mechanisms used in Wisconsin. Panelists will discuss Wisconsin’s innovative phosphorus compliance options and resulting policy implications, the economic effect of compliance for wastewater utilities, and whether Wisconsin policy is adequately addressing agricultural nutrient management.

    The afternoon also features case studies. A watershed program manager and farmer team from Oconomowoc will describe their experience with phosphorus management using the adaptive management compliance option. Next, a conservation specialist in Rock County and a utility director with the City of Janesville will share their experience managing phosphorus with the water quality trading compliance option.

    The conference closes with a roundup of key takeaways from the panel sessions. During this final address, we will reflect on remaining questions and research gaps with an eye toward future policy goals and research. There will be ample time for networking at the beginning and close of the day, as well as interacting with over 20 researchers presenting posters to communicate their findings.

    Where to Register

    For a more complete analysis of Wisconsin’s phosphorus rules and the impact to water quality, join the Center for Water Policy and co-hosts at Monona Terrace in Madison on Feb. 7, 2023, for Phosphorus: Lessons from 10+ Years of Numeric Standards for Wisconsin’s Waters. If we have reached capacity, register for virtual access to conference recordings and materials.


    1 U.S. Envtl. Prot. Agency, “State Progress Toward Developing Numeric Nutrient Water Quality Criteria for Nitrogen and Phosphorus,” Oct. 26, 2022.

    This article was originally published on the State Bar of Wisconsin’s Environmental Law Section Blog. Visit the State Bar sections or the Environmental Law Section webpages to learn more about the benefits of section membership.

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    Disclaimer: Views presented in blog posts are those of the blog post authors, not necessarily those of the Section or the State Bar of Wisconsin. Due to the rapidly changing nature of law and our reliance on information provided by outside sources, the State Bar of Wisconsin makes no warranty or guarantee concerning the accuracy or completeness of this content.

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