Water channel through marsh grasses in Galveston, Texas
A narrow channel flows through marsh grasses at Galveston Island State Park in Galveston, Texas. Credit: Stuart Villanueva/The Galveston County Daily News via AP

The Clean Water Act (CWA), which became law in 1972, is the primary federal mechanism by which streams, lakes, and wetlands are protected from degradation in the United States. The act is enforced in tandem by the U.S. Army Corps of Engineers and the Environmental Protection Agency (EPA; hereinafter referred to as “the agencies”) and requires that a permit be issued prior to dredging, filling, or discharging pollutants in “navigable waters.” On 23 January, the agencies released the Navigable Waters Protection Rule (NWPR), which details how the CWA will be enforced, including which waters receive federal protections under the act.

We argue that this rule blatantly ignores established science and risks degrading U.S. waters to the point that ecosystems may be permanently harmed.

We argue that this rule blatantly ignores established science—including the agencies’ own studies and syntheses—and risks degrading U.S. waters to the point that ecosystems may be permanently harmed. Moreover, the rule runs counter to its own goal to strike a “reasonable and appropriate balance between Federal and State waters” by shifting the cost and burden of analysis and enforcement to states.

A Brief History of the Clean Water Act

The CWA has always been controversial, especially for its notoriously vague definition of navigable waters: “waters of the United States, including the territorial seas.” Some argue that the definition of waters of the United States, often called WOTUS, should be broad, thus allowing the federal government to secure protections for intrastate waters, headwater streams (small streams connecting watersheds to main river channels), and isolated wetlands. Others believe that its definition should be narrow, leaving states to regulate these types of waters if they so choose, arguing state agencies would have better regionalized knowledge to manage their water resources. The ongoing battle for clarity continues to this day, as the agencies promulgate rules that establish CWA jurisdiction over certain waters and as those rules are subsequently checked by the courts.

In one of the most recent battles over the CWA, a controversial and influential 2006 U.S. Supreme Court split decision gave the agencies a new test for defining navigable waters. Rapanos v. United States involved penalties brought upon a shopping center developer for filling wetlands in Michigan. Chief Justice John Roberts chided the agencies for failing to develop a comprehensive rule to be used in defining the jurisdictional scope of the CWA. Justice Anthony Kennedy offered his own “significant nexus” test, establishing jurisdiction on the basis of physical, chemical, or biological connectivity linking a traditionally regulated water (e.g., a large river) to the water body being considered (e.g., a small tributary or nearby wetlands).

On the basis of instruction from the two justices, the agencies embarked on a massive analysis of available hydrological research [U.S. Environmental Protection Agency, 2015a] and in 2015 advanced the Clean Water Rule. Several state governments immediately balked, causing the Sixth Circuit Court of Appeals to halt the new rule’s implementation in 18 states. After a series of court cases—while 26 states operated under the new rule and, after several more states resisted it, 24 continued to operate under the 1986 rule it was supposed to replace—the Clean Water Rule was formally repealed last September.

The NWPR now replaces the Clean Water Rule as the latest attempt to define WOTUS.

What Did the Navigable Waters Protection Rule Change?

Since 1986, when new regulatory guidance was established in response to the decision in United States v. Riverside Bayview Homes, the agencies have used a WOTUS definition that relies on the delineation of “ordinary high water marks” to identify streams that fall under the protection of the CWA. Determining an ordinary high water mark requires evidence of regular flow from field observations, including debris lines, water staining, and other visual indicators. The NWPR replaces this definition with one requiring that a waterway exhibit perennial or intermittent flow to be protected. Unlike the 1986 rule, the NWPR explicitly excludes ephemeral waters (those that flow only in response to precipitation events), thus contracting the network of streams that were previously regulated.

What formerly involved a simple visual inspection in the field now requires more complex assessments of databases and models describing precipitation and resultant streamflow over rolling 30-year windows.

This change, however, is in direct opposition to EPA administrator Andrew Wheeler’s objective of streamlining the permitting process and increasing regulatory efficiency. What formerly involved a simple visual inspection in the field now requires more complex assessments of databases and models describing precipitation and resultant streamflow over rolling 30-year windows. Moreover, the rule leaves open the possibility that other models and forecasts may be acceptable forms of evidence to determine which waters are WOTUS, which we expect will seed a cottage industry of consulting firms touting competing models and, ultimately, litigation when models disagree.

Another definition from the 1986 rule specified that waters “adjacent” (clarified to mean “bordering, contiguous, or neighboring”) fell under protection of the act. This definition was typically interpreted to include anything from immediately adjacent lakes and wetlands sharing a surface water connection with regulated streams to waters within 500 feet (152.4 meters) of those streams, even if they didn’t have a visible overland connection. After Rapanos, the “significant nexus” test was added, meaning the body of water in question must have a biological, chemical, or physical connection with downstream, regulated waters. For example, a wetland could be considered regulatory because biota in a river spawn in shallow waters on the floodplain, forging a biological connection between the waters that is critical to the health of the river despite no persistent overland flow linking the two (see more examples in Cohen et al. [2016]).

The new rule changes the scope of lake and wetland jurisdiction in two important ways: (1) The NWPR revises the definition of “adjacent” so that only immediately adjacent lakes and wetlands sharing a surface water connection are federally protected, with no interpretation allowing for subsurface connections. This substantially reduces wetland protections via the CWA. (2) The NWPR eliminates case-by-case significant nexus tests, which proponents view as a win in terms of regulatory efficiency. We contend that this efficiency baits litigation and comes at the expense of the environment. The NWPR broadly takes all cases that would have required a test and makes the waters not jurisdictional by rule (i.e., they are “out,” and no consideration is required). These changes reduce federal regulatory coverage of national waters, as we discussed in detail last April [Walsh and Ward, 2019].

Water Protection Now Falls to States

The contraction in federal protections under the NWPR means that each state will need to determine what waters within its boundaries are no longer covered and whether adjustments are needed to its own current regulations. Some states may need to decide whether to continue enforcing their existing regulations that go beyond the now contracted federal rules. The agencies’ own economic analysis predicts several states will contract their protections to match those of the NWPR. Although other states may expand coverage, this process is not instant and will require scientific input and political will to achieve.

Wetlands have historically been carefully protected because they not only provide important habitat, store floodwater, prevent shoreline erosion, and improve water quality but are also comparable to rain forests and coral reefs in productivity.

Notably, these states will also accrue costs as a result of ecosystem service loss. Wetlands have historically been carefully protected because they not only provide important habitat, store floodwater, prevent shoreline erosion, and improve water quality but are also comparable to rain forests and coral reefs in productivity. These and other benefits have been estimated to generate up to $78,500 per acre each year [Costanza et al., 2014]. In states choosing to contract regulations to match those of the federal government, the loss of wetlands and their associated ecosystem services will mean that floods, water treatment, and erosion control will become more costly. Although the agencies’ recent economic analysis identified wetland loss as the single highest cost resulting from the NWPR, the value it estimated for wetlands was 80%–95% lower than values suggested by the agencies’ prior economic analysis of the Clean Water Rule [U.S. Environmental Protection Agency, 2015b].

One notable danger in shifting the regulatory power to the states is that most states lack the policy infrastructure to handle these new responsibilities. For example, Michigan and New Jersey are the only states that have opted to, and have been deemed capable by the agencies of, administering the federal wetland permitting program. In all other states, final permitting decisions for WOTUS wetlands have been made by the U.S. Army Corps of Engineers. In 48 states, the decision to maintain status quo wetland protections will necessitate hiring and training new staff to handle permit obligations. The administration’s economic analysis concluded that the NWPR will net cost savings for the federal government. However, this ignores real costs to the states. From the perspective of a taxpayer who wants to keep the previous level of water protections, there are new costs in having state and local agencies re-create enforcement and protection systems that existed nationwide a month ago.

In addition, there will be costs when issues involving interstate waters inevitably arise, whether these issues are addressed collaboratively or contentiously. Waters crossing state lines have been regulated by the federal government for decades, reducing the potential for state versus state legal disagreements. The elimination of these long-standing protections will undoubtedly result in legal costs undocumented by the economic analysis.

Five Important Shortcomings of the NWPR

1. The NWPR ignores the best available science.

The EPA has a Science Advisory Board that adheres to a code first laid out at the agency in 1999: “Science is the backbone of EPA’s decision-making.” However, when developing the NWPR, the agency elected to ignore its own science, including the 2015 report [U.S. Environmental Protection Agency, 2015a] based on more than 1,200 peer-reviewed papers from the hydrological community. The board admonished the blatant disregard of the science, commenting on the draft of the new rule, “These changes are proposed without a fully supportable scientific basis, while potentially introducing substantial new risks to human and environmental health.”

In a time when the averages and extremes of weather and streamflow frequency are shifting due to climate change, the concept of “typical” is antiquated at best and irresponsible at worst.

2. The NWPR does not account for climate-induced changes in waters.

The new rule includes protection for waters based on the frequency and duration of surface flow during a “typical year.” In a time when the averages and extremes of weather and streamflow frequency are shifting due to climate change, the concept of “typical” is antiquated at best and irresponsible at worst. Our recent study found that climate change caused a network of waters that would have fallen under CWA protection to contract by more than 10% when comparing two 30-year periods ending in 1982 and 2017 (A. Ward et al., Climate change causes network contraction and disconnection in the H. J. Andrews Experimental Forest, Oregon, USA, submitted to Hydroshare, 2019). A water body transitioning between protected and unprotected status in response to weather makes consistent regulation impossible.

3. The NWPR fails to recognize that sufficient data for regulation exist.

The reduced network of waters protected by the CWA under the new rule is in part based on the premise that there is no single, comprehensive database of WOTUS. We contend that no regulatory database can possibly be complete and that the agencies have a responsibility to use the best available data to write and enforce rules and to update those rules when new data become available. The assertion that incomplete data cannot be used for regulatory purposes makes the perfect the enemy of the good, and our environment will pay the price.

4. The NWPR ignores precedent.

The NWPR blatantly disregards the history that has shaped the governance and protection of water resources in this country. The United States has had a goal of no net loss of wetlands since 1989, with support from four presidents (two Democrats and two Republicans). That goal has ended with this rule and this administration. Similarly, the agencies have elected to ignore Kennedy’s opinion in Rapanos despite (1) having provided guidance based on this opinion in 2008 that regulators have been using since and (2) developing the Clean Water Rule in direct response to Kennedy’s opinion. Only under the current administration have the agencies favored the more restrictive interpretation of “navigable waters” favored by the conservative justices in that case. This willful disregard may be part of a strategy to ultimately bring the Clean Water Act back to the Supreme Court, which is now absent Kennedy.

5. The NWPR jeopardizes streams and wetlands.

Under the CWA, the agencies enforce mitigation rules if regulated waters are degraded or destroyed. This mitigation often takes the form of restoration, preservation, or construction of new waters that functionally replace losses. Although large streams and lakes will retain these protections and mitigation requirements, the cumulative losses of smaller or isolated waters threaten a death by a thousand cuts through permanent losses in sensitive, now vulnerable ecosystems.

We Need Science-Based Rules to Protect Waters

The continued politicization of science-based policy making threatens our environmental resilience, particularly in the face of climate change. We know more about the benefits of headwater streams and wetlands than ever before (see, e.g., EPA’s own science review [U.S. Environmental Protection Agency, 2015a] and a recent book on intermittent and ephemeral streams [Datry et al., 2017]). However, our elected representatives all too often ignore the science. Instead, partisan ideologies direct environmental management decisions that will reverberate for decades.

The NWPR is purported by its backers to establish balance and clarity between the states and the federal government. But it appears to be decisively unbalanced, saving federal dollars while placing new financial burdens—and promises of future court visits—on the states. Costly and case-by-case litigation is sure to arise from poorly defined terms that are difficult to enforce in a time when extremes are the new normal.

Finally, the promulgation of a new rule while the Supreme Court is actively deliberating on the jurisdictional scope of the CWA sets up a conflict that will require resolution in the courts. Now more than ever, we require environmental rule making anchored in an understanding of ecology, hydrology, and dynamic systems based on the best available science.


Cohen, M. J., et al. (2016), Do geographically isolated wetlands influence landscape functions?, Proc. Natl. Acad. Sci. U. S. A., 113(8), 1,978–, http://www.pnas.org/cgi/doi/10.1073/pnas.1512650113.

Costanza, R., et al. (2014), Changes in the global value of ecosystem services, Global Environ. Change, 26, 152–158, https://doi.org/10.1016/j.gloenvcha.2014.04.002.

Datry, T., N. Bonada, and A. Boulton (Eds.) (2017), Intermittent Rivers and Ephemeral Streams: Ecology and Management, 597 pp., Academic, London, https://doi.org/10.1016/B978-0-12-803835-2.09998-8.

U.S. Environmental Protection Agency (2015a), Connectivity of streams and wetlands to downstream waters: A review and synthesis of the scientific evidence, Rep. EPA/600/R-14/475F, Washington, D.C., cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=296414.

U.S. Environmental Protection Agency (2015b), Economic analysis of the EPA-Army Clean Water Rule, Washington, D.C., archive.epa.gov/epa/sites/production/files/2015-06/documents/508-final_clean_water_rule_economic_analysis_5-20-15.pdf.

Walsh, R., and A. S. Ward (2019), Redefining clean water regulations reduces protections for wetlands and jurisdictional uncertainty, Front. Water, 1, 1, https://doi.org/10.3389/frwa.2019.00001.

Author Information

Adam S. Ward (adamward@indiana.edu) and Riley Walsh, Indiana University, Bloomington. Adam S. Ward is a Science Adviser for Eos.


Ward, A. S.,Walsh, R. (2020), New Clean Water Act rule leaves U.S. waters vulnerable, Eos, 101, https://doi.org/10.1029/2020EO140022. Published on 11 February 2020.

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