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Ciaran Harman is an associate professor of landscape hydrology and the Russell Croft Faculty Scholar for the Johns Hopkins Department of Environmental Health and Engineering. His research focuses on how the structure of landscapes controls the movement of water from rainfall to streams, and how that structure evolves over time.
What do we need to know?
The federal Clean Water Act (CWA) protects our rivers, lakes, estuaries, and oceans from pollution. One way it does this is by requiring anyone who wants to discharge something into the "waters of the United States" to apply for a permit. State and federal agencies review these applications and will reject one if the discharge will harm the environment or public health.
But what exactly counts as the "waters of the United States", or WOTUS? If we want the CWA to protect Baltimore Harbor, but leave our backyard fishpond alone, where do we draw the line? In the U.S., this is a constitutional question because it determines what the federal government has jurisdiction over and what the limits of that jurisdiction are.
On Aug. 29, the U.S. Environmental Protection Agency (EPA) changed the official rule defining what kinds of water bodies are WOTUS and what are not. They were forced to do so by the Supreme Court, which ruled back in May of this year that the previous definition was too broad. Now that the new WOTUS rule is out, the will of the Supreme Court goes into effect.
What does this mean for environmental regulation going forward?
This change means that a lot of water bodies that were previously protected by the Clean Water Act won't be any more. Developers and industries will be able to pollute and destroy water bodies on their private property without having to apply for a permit under the CWA.
So which water bodies will be affected? It is important to understand that the CWA applies to "interstate navigable waters" and to the streams, lakes, wetlands, etc., they have a significant hydrological and ecological connection to. The new WOTUS rule changes the strength of the connection needed for the CWA to apply. The previous rule (based on a 2006 Supreme Court ruling) required that there be a "significant nexus" of connection, and recognized that water bodies connected primarily through groundwater or only intermittently through surface water can have a significant effect on downstream water quality.
The new rule requires a "continuous surface connection" to "traditional interstate navigable waters". That means that isolated wetlands and ephemeral streams are now excluded. Isolated wetlands may not have a continuous surface connection to an adjacent covered water body, but they are often connected through the groundwater system, and may connect temporarily during wet parts of the year or in large storms. Ephemeral streams are those that dry up part of the time, and only flow during wet periods.
What happens next?
Isolated wetlands and ephemeral streams serve important ecological purposes as breeding grounds for diverse species and rest stops for migratory birds. They also soak up the excess nutrients, sediment, contaminants, and pathogens washed into them and help protect us from flooding by storing some of the floodwaters.
Some have estimated that half of the wetlands of the U.S. have now lost protection. Without protection, developers will be able to fill in isolated wetlands, and polluting industries will be able to dump their waste into ephemeral streams. When that happens, you can expect to see a decline in water quality and possibly increases in flooding.