Rain-fed streams lacking federal protections are vital for water quality, study finds

By Shannon Kelleher

New data supports environmental advocates’ long-held position that small, rain-fed streams make major contributions to water quality in rivers and lakes across the US.

So-called “ephemeral streams,” which only flow after precipitation falls and are not currently protected under the Clean Water Act, contribute more than half of the water discharged from US regional rivers, according to the study, which published on Thursday in the journal Science. These streams are likely a major pathway for downstream water pollution, the study concluded.

The findings back concerns that a 2023 US Supreme Court decision in the case titled Sackett v. Environmental Protection Agency (EPA) may put many US waterways and communities living downstream at risk of exposure to pollutants. The ruling effectively removed federal protections for ephemeral streams and wetlands, narrowly defining “waters of the United States” as “relatively permanent, standing or continuously flowing bodies of water.”

The study provides “some scientific confirmation that pollution would flow significantly downstream from these smaller waterways,” said John Rumpler, clean water director and senior attorney for the organization Environment America.

“That’s a really important finding,” he said. “If polluters are allowed to dump into ephemeral streams with impunity and there’s no federal recourse, then downstream water quality can be dramatically impacted.”

The Supreme Court’s move to limit the Clean Water Act has been met with alarm by environmentalists and sharp criticism from the Biden administration, with President Joe Biden saying in a statement last May that it “upends the legal framework that has protected America’s waters for decades.”

A 2022 brief filed in the Supreme Court by 45 senators and 154 House members expressed support for more limited federal control in the Clean Water Act, siding with petitioners in the then-pending Sackett v. EPA case.