The water regulatory landscape is evolving rapidly as federal agencies, courts, states, and regulated entities adjust to shifting legal and policy priorities across the United States.
The U.S. Environmental Protection Agency, the U.S. Army Corps of Engineers, and state regulators have advanced significant changes affecting nearly every aspect of water regulation in recent months.
These changes span the scope of federal Clean Water Act jurisdiction, Section 401 certifications, stormwater regulation, PFAS drinking water rules, citizen enforcement, and water supply disputes across the western U.S.
In November 2025, EPA and the Corps proposed a new definition of “Waters of the United States,” the threshold jurisdictional term that triggers Clean Water Act jurisdiction, with the Administration now seeking supplemental public comment that will likely delay a final rule substantially.
Several states have stepped in to fill the jurisdictional gap left by EPA’s and the Corps’ push for a narrower WOTUS definition following the Supreme Court’s Sackett decision, with Colorado, California, and New York among those taking notable action.
In January 2026, EPA issued a Proposed Rule to revise its CWA Section 401 water quality certification regulations, receiving over 80,000 public comments by the February 17, 2026 deadline, though EPA has missed its June 2026 target for a final rule.
The Supreme Court’s decision in City and County of San Francisco v. EPA, 604 U.S. 334 (2025), held that the Clean Water Act does not allow EPA or states to impose “end result” requirements in NPDES permits that subject permittees to liability based on receiving water conditions.
On May 18, 2026, EPA announced two proposed rules that could reshape near-term implementation of PFAS drinking water requirements, including a proposal to retain the 4.0 parts per trillion Maximum Contaminant Levels for PFOA and PFOS while allowing eligible public water systems to request up to two additional years to comply.
EPA also proposed to rescind its regulatory determinations and remove related federal requirements for PFHxS, PFNA, HFPO-DA, commonly known as Gen-X, and the Hazard Index for mixtures containing two or more of those PFAS compounds.
In the Colorado River Basin, an approximately 2.59 million acre-foot gap between the river’s natural supply and consumptive use continues to push the reservoir system toward crisis, with Reclamation facing mounting pressure to balance storage against downstream delivery obligations.
Rio Grande Basin water users face similar challenges, with Elephant Butte Reservoir currently oscillating around 13% capacity, leaving serious doubts about whether basin states can meet their delivery obligations even under the recently approved groundwater-accounting settlement framework.
Industrial facilities and municipalities with stormwater operations should monitor permit developments in Oregon, Texas, and Louisiana, while EPA’s federal Multi-Sector General Permit remains in administrative continuation pending final action on the proposed 2026 MSGP.
Companies should also expect continued attention to CWA compliance issues reflected in the public record, as increased public access to compliance reporting databases has made it substantially easier for citizen groups to identify potential enforcement targets.