In recent years, environmental policy has been increasingly shaped by legal interpretations that omit critical waterways from protection. The 2023 Supreme Court ruling, which limited the scope of the Clean Water Act (CWA) to only those water bodies that are permanent and clearly navigable, marked a significant turning point. While on the surface this might seem like a narrow legal decision, its implications threaten to unravel the delicate fabric of the nation’s water systems. Beneath the surface, ephemeral streams—those that only carry water during rainfall—are playing an outsized role in maintaining the health of our rivers and lakes. Despite their importance, they have been largely invisible in environmental policymaking, and this invisibility may cost us dearly.
Ephemeral streams do not contain groundwater and usually appear as dry gullies or dried-up riverbeds during most of the year. They are triggered by precipitation, momentarily transforming from barren landforms into active waterways. These streams are often dismissed as insignificant or mere dry channels, but research reveals that they are crucial contributors to the hydrology of large river systems. When heavy rains fall, these dry gullies become active conduits that channel pollutants, sediments, and nutrients into major rivers. Ironically, the very nature that renders ephemeral streams seemingly unimportant—their intermittent flow—also makes them powerful agents of environmental change.
This underappreciation and the subsequent regulatory neglect become particularly critical when considering the latest flashpoints of legal jurisdiction. With the Supreme Court ruling, ephemeral streams are no longer protected under the CWA, which defines regulated waters as “relatively permanent” and “continuously flowing.” This legal interpretation effectively excludes the majority of ephemeral streams from federal oversight. As a result, activities like unregulated dumping, pollution runoff, and sediment displacement into these dry channels may now go unnoticed and unregulated, setting the stage for widespread environmental degradation.
Research from institutions such as the University of Massachusetts Amherst and Yale University intensifies the urgency of this issue. Their findings disclose that ephemeral streams are responsible for over half of the water flow in large river systems across the U.S., averaging around 55% of a river’s annual output. The distribution is uneven geographically, with especially high influence in Western states like Nevada and California, where ephemeral streams contribute up to 94% of the flow. The East Coast is not exempt; even in humid regions with abundant groundwater, ephemeral streams significantly impact water flow—accounting for more than half of the water reaching estuarine environments like Long Island Sound.
This substantial contribution challenges traditional perceptions that only perennial, continuously flowing streams matter in water quality management. The realization that dry or intermittently flowing streams play a dominant role in shaping river systems underscores a glaring oversight in current environmental protection frameworks. One might ask: if these ephemeral streams are so influential, how can their pollution be managed or mitigated if they fall outside legal protections?
The answer lies in understanding the interconnectedness of water systems. Pollutants and sediments that accumulate in ephemeral streams during dry periods are suddenly flushed downstream during rain events, often in high concentrations. These pulses of pollution can severely impair water quality, affect aquatic life, and accumulate in larger water bodies over time. In essence, neglecting ephemeral streams is akin to ignoring the roots of a tree while only tending to its branches. The health of major rivers and estuaries depends heavily on the condition of these often-overlooked tributaries.
From a legal perspective, this disconnect emphasizes an urgent need for redress. Some legal scholars, like Yale Law School professor Doug Kysar, suggest that federal authority could extend to ephemeral streams based on the constitutional basis of protecting interstate commerce and environmental health. Yet, practical enforcement and political will often lean toward leaving regulation at the state and local levels—an approach that is inherently inconsistent given the transboundary nature of water pollution. States may lack the incentives or resources to apply stringent protections for ephemeral streams when the downstream benefits extend beyond their jurisdictions.
The challenge lies not just in recognizing the significance of ephemeral streams but in integrating them into a cohesive water management strategy. This requires embracing scientific advancements, such as hydrological modeling, to predict these streams’ contributions accurately. The models indicate that, at their current recognized scales, ephemeral streams influence a surprising majority of river flow—even in large basins. This acknowledgment should catalyze a rethinking of environmental laws, pushing policymakers to include these critical waterways in regulatory frameworks, rather than continuing to treat them as invisible or insignificant.
Ultimately, the oversight of ephemeral streams exemplifies a broader societal tendency to undervalue complex natural systems that do not fit conventional categories. This blind spot not only imperils water quality and ecosystem health but also reflects a fundamental failure to understand the interconnectedness of environmental processes. As water systems increasingly face threats from pollution, climate change, and urbanization, the neglect of ephemeral streams can no longer be justified. If we are to protect America’s waterways effectively, acknowledging and regulating these hidden arteries isn’t just a good idea—it is an imperative for sustainable environmental stewardship.