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Clean Water Act leaves about 55% of water flowing out of rivers vulnerable to pollution, study suggests

Clean Water Act leaves about 55% of water flowing out of rivers

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Clean Water Act Leaves: Impact of Clean Water Act on River Pollution

Clean Water Act leaves about 55% of water flowing out of rivers vulnerable to pollution, new study suggests
Clean Water Act Ephemeral vs. non-ephemeral streams that make up the Connecticut River basin. “On a day in which every stream in the Connecticut River is flowing with its average annual condition, 59% of the water entering Long Island Sound was sourced from these ephemeral streams—a.k.a., dry gullies in the woods,” Gleason says. Credit: Craig B. Brinkerhoff

The Clean Water Act and Ephemeral Streams

Clean Water Act A 2023 Supreme Court decision exempted ephemeral streams, rivers that respond only to weather, from Clean Water Act protections. New research from UMass Amherst suggests this leaves many US waterways exposed to pollution.

UMass Amherst’s Colin Gleason, a civil and environmental engineering professor and co-author of the paper, highlights the Connecticut River.

The Connecticut Department of Environmental Protection (or relevant agency) regulates the dumping of sediments, nutrients, and pollutants into the river by specifying permitted locations and allowable types. “Just dumping waste in a dry gully uphill risks polluting the very Connecticut River you’re trying to save when it rains.”

Impact on River Systems

While perennial streams flow continually, an ephemeral stream does not contain groundwater, so these non-perennial streams only run when they fill up with rain.

The researchers set out to determine just how much water these sometimes-dry river beds contribute to a river system’s total output.

They found that, on average, ephemeral streams contribute 55% of the water that comes out of the mouth of regional river systems across the United States, but there is a strong east-west divide.

River basins west of the Mississippi are more influenced by ephemeral streams than eastern rivers. For instance, 94% of the water coming out of the river systems in Black Rock Desert, Nevada, and Humboldt County, California, comes from ephemeral streams.

This makes sense, says Brinkerhoff. “Normally, when we think about ephemeral streams, we think of dry riverbeds in the desert,” he explains. “The groundwater table is always way below the land surface.”

Researchers were surprised to discover just how influential these ephemeral streams were on the East Coast as well. Brinkerhoff continues, saying “Even on the East Coast, even in a humid place with a ton of groundwater, ephemeral streams still exert a big influence.”

94% of the water coming out of the river systems in Black Rock Desert, Nevada, and Humboldt County, California, comes from ephemeral streams. Credit: Craig Brinkerhoff

Impact of Supreme Court Ruling

Gleason uses his home watershed as an example. He explains, “When all the streams in the Connecticut River are flowing at their average annual rate, ephemeral streams (dry gullies in the woods) contribute 59% of the water entering Long Island Sound.”

However, the Clean Water Act (CWA) no longer regulates these ephemeral streams. Last summer, in the case of “Sackett v.The Supreme Court, in a majority decision, limited protected waters under the Clean Water Act (CWA) to those that are relatively permanent, such as streams, oceans, rivers, and lakes. These water bodies must be either standing or continuously flowing, and form recognizable geographical features.

Implications for Water Pollution

“The Clean Water Act regulates where and how much we can dump into water bodies—water bodies being rivers, lakes, wetlands, reservoirs, etc.,” says Brinkerhoff. And the implications of this new research for water pollution are clear.

“[Ephemeral streams are] not flowing most of the time, but then you get a big enough rainstorm, and all of a sudden you’re pushing the stuff that’s been accumulating in those rivers downstream. In theory, pollution in those ephemeral streams will ultimately influence water many kilometers away that is, at least nominally, still regulated by the Clean Water Act,” he says.

Clean Water Act Legal and Regulatory Challenges

Doug Kysar, Joseph M. Field Professor of Law at Yale Law School, and one of the study’s authors, says that this work helps provide a constitutional basis to include ephemeral streams in the CWA.

“Water pollution can cross state lines, affecting trade between states. This allows Congress to regulate even small streams that don’t always flow.”

However, he also says that it’s more likely that this responsibility will fall to state and local governments.

The federal Clean Water Act was adopted because state and local governments did not adequately protect the nation’s waterways, according to him.

Our research reveals the far-reaching consequences of pollution in ephemeral waterways. It demonstrates how impacts can be felt far downstream, even beyond state borders. This explains why states might be hesitant to adopt expensive water protections when the benefits accrue to ecosystems outside their jurisdiction.

Research Methodology

Hydrologists modeled ephemeral streams across the US, estimating their contribution to annual river flow.

One thing the researchers emphasize is that the size of the river basin used for their modeling does influence the results. The 55% figure is only true when you divide river basins into a certain size—if they had used smaller basins, the ephemeral influence would be larger, and if they used bigger basins, the influence would be less.

Clean Water Act Findings and Significance

But even using the scale they did—which is the second-largest river basin scale defined by the U.S. Geological Survey—ephemeral streams still influenced more than half of rivers’ total water output. In other words, 55% is a quite surprising finding for rivers so large, the researchers say. Previous thinking was that ephemeral streams only influence their immediate areas.

“Our study provides more concrete evidence that all of these things are connected,” says Brinkerhoff. “We can’t regulate water bodies ad hoc.”

More information:
Craig B. Brinkerhoff, Ephemeral stream water contributions to United States drainage networks, Science (2024). DOI: 10.1126/science.adg9430. www.science.org/doi/10.1126/science.adg9430

Provided by
University of Massachusetts Amherst

Citation:
Clean Water Act leaves about 55% of water flowing out of rivers vulnerable to pollution, study suggests (2024, June 27)
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