Streams Critical to Des Moines’ Drinking Water No Longer Protected by the Clean Water Act – New Research

DES MOINES, Va. - More than a third - 36% - of the water in the Raccoon River comes from smaller streams that are no longer protected by the Clean Water Act. In the Des Moines River, these newly-unprotected streams provide 26% of the total flow, according to new research from Yale and the University of Massachusetts.

"The loss of these long-standing protections make it that much more complicated to clean up our drinking water at the source," said Ryan Smith, executive director of the Iowa Wildlife Federation. "These streams may be small but they have a meaningful impact on water quality - sending nitrates, pesticides and other pollutants downstream every time it rains."

The Supreme Court ruled in 2023 that streams can only be protected under the federal Clean Water Act if they are "relatively permanent," which excludes ephemeral streams that only flow after rainfall or snowmelt.

"Our research shows that small streams exert a meaningful influence on downstream, larger rivers, including systems that supply drinking water," said Craig Brinkerhoff, a river scientist and engineer at Yale. "All of these waters are connected. If enough of these streams were polluted or damaged, it could potentially impact Des Moines' drinking water supplies over the long run."

This new analysis of Iowa's streams used models originally created for research published in the journal Science. The models do not fully account for tile drainage, which can influence the magnitude, timing, and frequency of stream flow.

Nitrate levels in the Des Moines and Raccoon rivers have exceeded the federal maximums of 10 mg/L for most of 2026. Central Iowa Water Works has been running its world-class nitrate treatment plant for most of the year - which can cost up to $16,000 a day - and the utility recently announced a ban on lawn watering for the second summer in a row.

The EPA is currently finalizing a rule that will officially exclude ephemeral streams and 95 percent of Iowa's wetlands from protection under the Clean Water Act.

"Healthy streams and wetlands naturally remove nitrate from water. EPA and the Supreme Court are putting our free water purification systems at risk just when we need them the most," said Smith.

EPA documents acknowledge that loss of protections for these streams and wetlands could increase the cost to treat raw water to drinking water standards, but did not include these impacts in its official cost-benefit analysis.

"These Clean Water Act rollbacks will increase the risk of unsafe tap water and will increase the costs to consumers," said Jessie Ritter, Associate Vice President of Water Policy at the National Wildlife Federation. "It's a double-whammy that we are losing these longstanding protections at the same time the President's budget proposes deep cuts to water treatment funding. These rollbacks will put Iowans at greater risk."

Additional Resources:

• Ephemeral stream water contributions to United States drainage networks, Science
• Study Finds Small Streams, Recently Stripped of Protections, Are a Big Deal, New York Times
• Half the water flowing from US rivers is at risk of pollution due to lax federal regulation: Study, The Hill
• US Rivers' Total Water Output at Pollution Risk, Study Warns, Newsweek