Impaired waters list serves as a tool to prioritize local restoration efforts

DES MOINES — The Iowa Department of Natural Resources is seeking comment on the draft Integrated Report on water quality, initiating a 30-day public comment period.

This biennial report, required by the federal Clean Water Act, acts as a road map for Iowa’s rivers, lakes, and streams, identifying which water bodies are meeting their designated goals for recreation, fishing, and drinking water.

This report covers data for 2022-2024 for streams and 2020-2024 for lakes.

In this cycle, the DNR assessed more than 213,000 water quality results covering 61 parameters. The number of impairments has been relatively stable from 2014 to 2024, as stream segments or lakes can come on and off the list from one report to the next. In total, the 303(d) list shows a net reduction of three impaired segments from the list submitted by DNR in 2024.

Portions of both the Iowa and Raccoon Rivers are now impaired for nitrates.

The Integrated Report is developed using credible data gathered through several water monitoring programs. Water samples are collected to establish baseline data on the physical, chemical, and biological characteristics of Iowa streams, lakes, and wetlands. The DNR collects data on water temperature, dissolved oxygen, pH, and other physical and chemical parameters.

Additional data are analyzed before assessing a segment, including the DNR’s Supplemental Streams Monitoring program; the DNR’s Fish Kill Database; data collected by federal partners, such as the US Geological Survey; data collected by municipalities; and data collected on the border rivers by adjacent states. This data is available at programs.iowadnr.gov/aquia/.

A common misconception is that a "listed" or "impaired" body of water is toxic or unusable. In reality, an impairment is used to prioritize resources based on its “designated uses” or the specific job the water is meant to perform.

If one parameter does not meet its intended use, the water segment is impaired. The designated uses are as follows:

•Recreation (Class A): Is this water body safe for swimming?

•Aquatic Life (Class B): Can fish, insects, and other creatures live there safely?

•Drinking Water (Class C): Is this a safe source for drinking water treatment?

•Human Health (Class HH): Are the fish caught safe to eat?

"The Impaired Waters List is not merely a record of impaired waterbodies; it is a problem-identifying tool and a road map for restoration," said Mark Moeller, DNR’s water quality monitoring and assessment supervisor. "A waterbody can be listed for failing just one specific parameter, while remaining healthy for other uses like fishing or kayaking."

The status of a body of water is not permanent; a segment can be removed from the impaired list if new data shows it meets the designated uses or if the DNR develops a Total Maximum Daily Load.

A TMDL is a "pollution budget" that sets safety standards and guides restoration efforts, including industrial permit limits and conservation practices. This report uses data for streams from 2022-2024 and for lakes from 2020-2024, and it does not include 2025 data.

Public comment is welcome through March 19 and should be sent to IRcomment@dnr.iowa.gov.