Commission hears monitoring results showing lower phosphorus concentrations; presenter says Pheasant Branch meets state phosphorus criterion two years running

Presenter (speaker 2) delivered a detailed monitoring update for the Pheasant Branch watershed and Confluence Pond covering water year 2025. Key findings included slightly above‑average precipitation for the year, rising runoff volumes, continuing decreases in long‑term sediment loads at key monitoring stations, and mixed trends in flood peaks.

The presenter said the North Fork contributed the majority of phosphorus entering Confluence Pond in 2025, accounting for approximately 72% of the load, and reported that Confluence Pond trapped about 62–63% of incoming sediment and roughly 51% of phosphorus for the year.

On stream health, the presenter said that the median May–October phosphorus concentration for Pheasant Branch was below 0.075 milligrams per liter for the second consecutive year. "The median phosphorus loads show that the Pheasant Branch could now be classified as a healthy stream, again, for the second year in a row," the presenter said. Commission members cautioned that regulatory delisting requires DNR review and sustained monitoring data; staff and USGS data collection were noted as the sources used for the analysis.

Members discussed implications for Lake Mendota loading (the presentation noted that Pheasant Branch is a significant contributor of phosphorus to the lake) and emphasized that phosphorus reductions do not necessarily address other issues such as bacteria, heavy metals or PCBs. The presenter and staff agreed that the finding is promising but that DNR procedures and additional monitoring would guide any formal change in impairment listings.

Commissioners requested that staff continue monitoring and that the data be packaged for any DNR review or delisting consideration.