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Hydrological Connectivity of Headwaters to Downstream Waters

By Tracie-Lynn Nadeau and Mark C. Rains, Lead Environmental Scientist, U.S. Environmental Protection Agency, Office of Wetlands, Oceans and Watersheds; and Assistant Professor, University of South Florida, Department of Geology from the Journal of the American Water Resources Association (JAWRA).

In January 2001, the U.S. Supreme Court issued a ruling in the case of Solid Waste Agency of Northern Cook County v. U.S. Army Corps of Engineers, 531 U.S. 159 (2001) (SWANCC). The SWANCC case presented the Court with two issues: (1) whether an isolated water could be considered part of the “waters of the United States,” protected under the Clean Water Act (CWA) – and thus subject to the U.S. Army Corps of Engineers’ (Corps) regulatory authority under Section 404 of the CWA – solely based on its use by migratory birds; and, if so, (2) whether Congress had the constitutional authority under the Commerce Clause to include these as waters of the United States. In particular, the Court considered the Corps’ Migratory Bird Rule – which deemed waters of the United States to include isolated intrastate waters that provide habitat for migratory birds. In a 5-4 decision, the Court found that the Migratory Bird Rule exceeded the Corps’ authority under the CWA [531 U.S., 159 (2001)], and held that the CWA is not intended to protect isolated, intrastate, non-navigable waters based solely on their use by migratory birds. While the Court’s decision did not create a bright line test for what Congress intended to regulate under the CWA, the Court’s reasoning implies that the CWA intended some “connection” to navigability, and that isolated waters need a “significant nexus” to navigable waters to be jurisdictional.

The SWANCC decision has had profound implications on the legal status of so-called isolated waters – those lacking a surface water connection to other bodies of water. Furthermore, that decision affects all CWA programs – including Section 303 water quality standards, Section 311 oil spill prevention and clean-up, Section 401 water quality certification, and Section 402 pollution discharge permits – not just Section 404, which regulates the discharge of dredged or fill material into waters of the U.S, including wetlands. Initially following the SWANCC decision, much of the regulatory debate was focused on so-called isolated wetlands, while the debate in the courts focused on the jurisdictional status of tributaries, including headwater, intermittent and ephemeral streams. These case law and regulatory debates made apparent that the emerging issue is “what is the extent of the tributary system,” with a focus on headwater, intermittent and ephemeral streams and the connectivity, or “significant nexus,” of these waters to navigable waters. The Corps and the U.S. Environmental Protection Agency issued guidance in January 2003 indicating that field staff were to continue to assert jurisdiction over tributaries and their adjacent wetlands, and that formal headquarters approval should be obtained prior to asserting jurisdiction over isolated waters based solely on links to interstate commerce [68 Fed. Reg. 1995, 1998 (January 15, 2003)]. During that same time period, a significant majority of courts, including 17 appellate court decisions, concluded that SWANCC was narrowly focused on isolated waters, and did not change the jurisdictional status of tributaries or adjacent wetlands.

On October 2005, the U.S. Supreme Court agreed to review two cases related to SWANCC, the John A. Rapanos etal. v. United States (U.S., No. 04-1034, 2005) and June Carabell etal. v. United States Army Corps of Engineers and the United States Environmental Protection Agency (U.S., No. 04-1384, 2005) decisions from the Sixth Circuit. By granting review of these appellate court decisions, the Supreme Court increased uncertainty about the extent to which the CWA protected tributaries, and the jurisdictional status of headwater, ephemeral and intermittent streams. The consolidated cases were heard on February 21, 2006. The petitioners argued that CWA jurisdiction extends only to wetlands that actually abut navigable-in-fact waters, and that if the CWA extends to any other wetlands, Congress has exceeded its Commerce Clause authority. The petitioners also argued that CWA jurisdiction does not extend to non-navigable tributaries. As this JAWRA featured collection was under review, the Supreme Court handed down its judgment in these consolidated cases in five separate opinions, none of which had a majority of five votes, 126 S. Ct. 2008 (2006) (Rapanos). The 4-1-4 decision is extremely complex, and has left many questions, some highly technical in nature, regarding CWA jurisdiction over headwater, intermittent, and ephemeral streams.

Given the debate over non-navigable waters and the regulatory turmoil caused by the SWANCC and Rapanos decisions, as well as the scientific, legal, and political complexities of CWA jurisdiction, now is an opportune time to review the state of our scientific understanding of the contributions of headwater, intermittent and ephemeral streams to the integrity of downstream waters. This featured collection of the Journal of the American Water Resources Association provides such a review. One motivation for this featured collection is that scientific information will be useful for on-going policymaking, at the federal, state, and local level. Another primary motivation for the featured collection is the need to address the more basic questions of hydrological and ecological connectivity of headwaters, how such connectivity contributes to the integrity of downstream waters, and to assess our knowledge of the processes that occur in these waters and the impacts they have on the larger aquatic ecosystem. This featured collection is based on an invited special session exploring the roles played by headwaters in maintaining the physical, chemical, and biological integrity of waters in lower watershed positions, held at the American Water Resources Association Annual Conference in Seattle, Washington in November, 2005. Participants were asked to address several key topics in preparing their presentations, and subsequent manuscripts, focused on the roles played by headwater streams in maintaining the physical, chemical, and biological integrity of downstream waters, the roles played by headwater streams in maintaining the integrity of the larger stream network, the spatial and temporal scales over which this hydrological connectivity is relevant, and the relative roles of surface water and ground-water flow paths.

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