By Jon Mueller, for the Bay Journal News Service

The Supreme Court has once again waded into the debate over the reach of the Clean Water Act. How the courts rule could determine the fate of thousands of acres of wetlands and tens of thousands of miles of small streams critical to the health of the Chesapeake Bay and its tributaries.

The high court heard oral arguments in Sackett v. EPA on Oct. 3. The long-running case involves an Idaho couple whom the U.S. Environmental Protection Agency sanctioned for filling in wetlands on their property without a permit. At issue broadly is how the agency determines which waters are protected by the federal Clean Water Act — and which aren’t.

This is important because the federal government can only safeguard waters covered by the landmark law, which aims to protect and restore water quality across the country. But the 50-year-old statute does not explicitly say which “waters of the United States” it empowered the government to regulate.

The Sacketts and their supporters insist that the EPA may only oversee “navigable” waterbodies connected by surface water. This view ignores the scientific fact that all waters in a drainage basin are connected, even if only underground (a point the Chesapeake Bay Foundation and other environmental groups made in a joint amicus brief they filed in the case).

The narrower interpretation by the Sacketts would also leave vulnerable to destruction several categories of “non-navigable” waters that are nonetheless critical to restoring and protecting the Bay ecosystem. Among them are pocosins and isolated freshwater wetlands unique to the watershed: Delmarva bays (also called Delmarva potholes).

Delmarva bays are shallow, oval-shaped depressions scattered over the Delmarva Peninsula, most of them clustered on the Delaware-Maryland border. The 5,000 or so known Delmarva bays, covering 34,560 acres, contain forested wetlands, according to a 2014 report in the journal Wetlands. Pocosins, which in the Bay watershed are found only in Virginia, are isolated bogs with sandy, peat soils.

Wetlands, in general, are critical to restoring the Bay because they trap pollutants running off farmland, parking lots and city streets before they can reach the estimated 111,000 miles of local streams, creeks and rivers that empty into the Bay.

Wetlands also provide essential habitat for fish and wildlife that support the region’s multibillion-dollar seafood industry and thriving outdoor recreation and tourism sectors.

By absorbing storm surges and floodwaters like sponges, wetlands protect coastal communities from climate change effects like sea-level rise and “sunny day” flooding that threaten lives, businesses and property.

Another category of nonnavigable waters at risk — and important to Bay restoration — is streams that only run at certain times of the year (known as “intermittent” streams) or after it rains or snows (“ephemeral” streams).

While you can’t navigate a boat on them, the science is clear that they are connected to downstream rivers. This hydrological connection means they can affect water quality downstream, just like streams connected above ground that run year-round.

Virginia and Pennsylvania have the most miles of intermittent and ephemeral streams. A staggering 59 percent of linear stream miles in Virginia (55,589 miles out of 94,914 miles) are intermittent or ephemeral streams, according to the EPA. In Pennsylvania, 41 percent of linear stream miles (30,148 miles out of 74,247 miles) only run seasonally or after rain or snow, according to a 2013 EPA report.

If the Supreme Court decides that the Clean Water Act doesn’t protect Delmarva bays, pocosins or intermittent and ephemeral streams, Maryland, Pennsylvania and Virginia have state regulations that could offer some protection. But loopholes, waivers and limited enforcement by state officials would leave many of these wetlands and waterways at risk.

The danger is greatest in Delaware, which follows the federal definition of covered waters. Delaware estimates that approximately 30,000 acres of its isolated wetlands, including 1,500 acres of Delmarva bays, are unregulated and therefore could be destroyed. Nor does the First State regulate activities in ephemeral streams, according to its Department of Natural Resources and Environmental Control.

Although the Supreme Court heard oral arguments in the Sackett case on Oct. 3, it is not expected to issue a ruling for several months, perhaps as late as next June.

In the meantime, the Biden administration is drafting another rule to define wetlands and other waterbodies protected by the Clean Water Act. The move has drawn strong criticism from the Sacketts’ supporters in Congress, who want the Supreme Court to weigh in first. In addition to its amicus brief to the high court, the Chesapeake Bay Foundation and a host of water-quality groups earlier this year submitted comments on the rule to the EPA, urging the agency to protect isolated wetlands, including Delmarva bays, pocosins and seasonal streams.

It’s unclear if the new rule or the court’s decision will finally settle this question or start a new round of time-consuming litigation that only prolongs the uncertainty for both regulators and the regulated community. What is clear are the significant stakes for the Bay, its tributaries and the more than 18 million people who live, work and play in its watershed. Without federal protections for all waterbodies critical to the cleanup, our ability to save the Bay is also at risk.

Jon Mueller is vice president for litigation at the Chesapeake Bay Foundation.

His views do not necessarily reflect those of the Bay Journal.