DNR recommends moving Prairie River to "cool" classification after multi‑year study

Michigan Department of Natural Resources fisheries staff told the Water Use Advisory Council they will recommend reclassifying a stretch of the Prairie River (Branch County) from its current "warm" designation to "cool" after multi‑year temperature logger, fish survey and connectivity work.

DNR presenter Jay Wesley summarized four years of temperature monitoring and fish surveys across five logger stations in the watershed. He reported that combined July mean temperatures across sites and years produced a July mean near 68.9°F, which the council’s temperature‑classification tool classifies as "cool." The DNR also recorded trout and other cold‑water species at downstream sites that gain groundwater.

"The most recent data and the recommendation I would give is to move it to cool and that would also match up with the downstream water management area that is also cool," the DNR presenter said. He and other staff described variability between stations and years; in 2025 the system ran warmer and drier, illustrating how annual climate variability affects the classification.

DNR and contracted data‑collection teams installed temperature loggers, ran gain/loss and connectivity surveys, and completed fish surveys that documented trout presence. One contractor (Kaiser Associates) produced annual reports and a final dataset used in the council presentation. DNR staff acknowledged that localized channel modifications and dredging by the county in one reach altered stream–groundwater connectivity and influenced temperature patterns in that reach; those human changes were discussed as part of interpreting spatial variability.

Council technical members and contractors supported the DNR assessment’s robustness. "The work that we did also supports that designation…for what it's worth the work that we did also supports that designation…it's a pretty robust data set," a field monitoring presenter said, echoing the teams that alternated temperature logger deployments and recorded connectivity and discharge data.

The recommended path to change the classification follows a public process: the department plans to present information and take public comment through the Natural Resources Commission (NRC) agenda cycle (information one month, action the next), or the director may forward a decision. The change would alter allowable index‑flow reductions and could have material consequences for withdrawals in the management area, a number of council members cautioned.

Next steps: DNR will consider whether more targeted monitoring or additional cross‑sections are needed, finalize its NRC or director‑level submittal, and provide public notice and opportunities for comment. The council’s data committee said it will review lessons learned from the Prairie River effort and consider recommending guidance on monitoring protocols and minimal datasets for future reclassification efforts.